diff --git a/ports/atmel-samd/boards/hallowing_m4_express/board.c b/ports/atmel-samd/boards/hallowing_m4_express/board.c
index 5d1ef6d9be..6bb2a591f0 100644
--- a/ports/atmel-samd/boards/hallowing_m4_express/board.c
+++ b/ports/atmel-samd/boards/hallowing_m4_express/board.c
@@ -49,7 +49,7 @@ uint8_t display_init_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_PA01, &pin_PA00, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_PA01, &pin_PA00, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/atmel-samd/boards/monster_m4sk/board.c b/ports/atmel-samd/boards/monster_m4sk/board.c
index 40141ca157..2377f4a9da 100644
--- a/ports/atmel-samd/boards/monster_m4sk/board.c
+++ b/ports/atmel-samd/boards/monster_m4sk/board.c
@@ -50,7 +50,7 @@ uint8_t display_init_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_PA13, &pin_PA12, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_PA13, &pin_PA12, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/atmel-samd/boards/openbook_m4/board.c b/ports/atmel-samd/boards/openbook_m4/board.c
index 85a5888799..2d9b316474 100644
--- a/ports/atmel-samd/boards/openbook_m4/board.c
+++ b/ports/atmel-samd/boards/openbook_m4/board.c
@@ -55,7 +55,7 @@ uint8_t stop_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB15, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB15, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/atmel-samd/boards/pewpew_m4/board.c b/ports/atmel-samd/boards/pewpew_m4/board.c
index 1872d18763..5f5a01e48e 100644
--- a/ports/atmel-samd/boards/pewpew_m4/board.c
+++ b/ports/atmel-samd/boards/pewpew_m4/board.c
@@ -97,7 +97,7 @@ uint8_t display_init_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_PA13, &pin_PA15, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_PA13, &pin_PA15, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/atmel-samd/boards/pybadge/board.c b/ports/atmel-samd/boards/pybadge/board.c
index 28e1aec131..bead06f3c6 100644
--- a/ports/atmel-samd/boards/pybadge/board.c
+++ b/ports/atmel-samd/boards/pybadge/board.c
@@ -72,7 +72,7 @@ uint8_t display_init_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB15, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB15, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/atmel-samd/boards/pybadge_airlift/board.c b/ports/atmel-samd/boards/pybadge_airlift/board.c
index fbb4441f0e..061f3d7772 100644
--- a/ports/atmel-samd/boards/pybadge_airlift/board.c
+++ b/ports/atmel-samd/boards/pybadge_airlift/board.c
@@ -50,7 +50,7 @@ uint8_t display_init_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB15, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB15, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/atmel-samd/boards/pygamer/board.c b/ports/atmel-samd/boards/pygamer/board.c
index c052614dbb..70d4a05dcd 100644
--- a/ports/atmel-samd/boards/pygamer/board.c
+++ b/ports/atmel-samd/boards/pygamer/board.c
@@ -72,7 +72,7 @@ uint8_t display_init_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB15, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB15, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/atmel-samd/boards/pygamer_advance/board.c b/ports/atmel-samd/boards/pygamer_advance/board.c
index a138c7e504..ff2da34a26 100644
--- a/ports/atmel-samd/boards/pygamer_advance/board.c
+++ b/ports/atmel-samd/boards/pygamer_advance/board.c
@@ -50,7 +50,7 @@ uint8_t display_init_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB12, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_PB13, &pin_PB12, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/atmel-samd/common-hal/analogio/AnalogIn.c b/ports/atmel-samd/common-hal/analogio/AnalogIn.c
index fc11d5d19f..2bd218cdda 100644
--- a/ports/atmel-samd/common-hal/analogio/AnalogIn.c
+++ b/ports/atmel-samd/common-hal/analogio/AnalogIn.c
@@ -73,7 +73,7 @@ void common_hal_analogio_analogin_construct(analogio_analogin_obj_t* self,
 }
 
 bool common_hal_analogio_analogin_deinited(analogio_analogin_obj_t *self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
@@ -81,7 +81,7 @@ void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
         return;
     }
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 void analogin_reset() {
diff --git a/ports/atmel-samd/common-hal/audiobusio/I2SOut.c b/ports/atmel-samd/common-hal/audiobusio/I2SOut.c
index 05a6aaf7b0..99d3762cbf 100644
--- a/ports/atmel-samd/common-hal/audiobusio/I2SOut.c
+++ b/ports/atmel-samd/common-hal/audiobusio/I2SOut.c
@@ -204,7 +204,7 @@ void common_hal_audiobusio_i2sout_construct(audiobusio_i2sout_obj_t* self,
 }
 
 bool common_hal_audiobusio_i2sout_deinited(audiobusio_i2sout_obj_t* self) {
-    return self->bit_clock == mp_const_none;
+    return self->bit_clock == NULL;
 }
 
 void common_hal_audiobusio_i2sout_deinit(audiobusio_i2sout_obj_t* self) {
@@ -213,11 +213,11 @@ void common_hal_audiobusio_i2sout_deinit(audiobusio_i2sout_obj_t* self) {
     }
 
     reset_pin_number(self->bit_clock->number);
-    self->bit_clock = mp_const_none;
+    self->bit_clock = NULL;
     reset_pin_number(self->word_select->number);
-    self->word_select = mp_const_none;
+    self->word_select = NULL;
     reset_pin_number(self->data->number);
-    self->data = mp_const_none;
+    self->data = NULL;
 }
 
 void common_hal_audiobusio_i2sout_play(audiobusio_i2sout_obj_t* self,
diff --git a/ports/atmel-samd/common-hal/audiobusio/PDMIn.c b/ports/atmel-samd/common-hal/audiobusio/PDMIn.c
index 3a51cce8f1..f70f1fec0d 100644
--- a/ports/atmel-samd/common-hal/audiobusio/PDMIn.c
+++ b/ports/atmel-samd/common-hal/audiobusio/PDMIn.c
@@ -219,7 +219,7 @@ void common_hal_audiobusio_pdmin_construct(audiobusio_pdmin_obj_t* self,
 }
 
 bool common_hal_audiobusio_pdmin_deinited(audiobusio_pdmin_obj_t* self) {
-    return self->clock_pin == mp_const_none;
+    return self->clock_pin == NULL;
 }
 
 void common_hal_audiobusio_pdmin_deinit(audiobusio_pdmin_obj_t* self) {
@@ -237,8 +237,8 @@ void common_hal_audiobusio_pdmin_deinit(audiobusio_pdmin_obj_t* self) {
 
     reset_pin_number(self->clock_pin->number);
     reset_pin_number(self->data_pin->number);
-    self->clock_pin = mp_const_none;
-    self->data_pin = mp_const_none;
+    self->clock_pin = NULL;
+    self->data_pin = NULL;
 }
 
 uint8_t common_hal_audiobusio_pdmin_get_bit_depth(audiobusio_pdmin_obj_t* self) {
diff --git a/ports/atmel-samd/common-hal/audioio/AudioOut.c b/ports/atmel-samd/common-hal/audioio/AudioOut.c
index b75c2b3350..1d9b4cbe8f 100644
--- a/ports/atmel-samd/common-hal/audioio/AudioOut.c
+++ b/ports/atmel-samd/common-hal/audioio/AudioOut.c
@@ -304,7 +304,7 @@ void common_hal_audioio_audioout_construct(audioio_audioout_obj_t* self,
 }
 
 bool common_hal_audioio_audioout_deinited(audioio_audioout_obj_t* self) {
-    return self->left_channel == mp_const_none;
+    return self->left_channel == NULL;
 }
 
 void common_hal_audioio_audioout_deinit(audioio_audioout_obj_t* self) {
@@ -332,10 +332,10 @@ void common_hal_audioio_audioout_deinit(audioio_audioout_obj_t* self) {
     tc_set_enable(tc_insts[self->tc_index], false);
 
     reset_pin_number(self->left_channel->number);
-    self->left_channel = mp_const_none;
+    self->left_channel = NULL;
     #ifdef SAMD51
     reset_pin_number(self->right_channel->number);
-    self->right_channel = mp_const_none;
+    self->right_channel = NULL;
     #endif
 }
 
diff --git a/ports/atmel-samd/common-hal/busio/SPI.c b/ports/atmel-samd/common-hal/busio/SPI.c
index 7a1426bedc..1dc389027d 100644
--- a/ports/atmel-samd/common-hal/busio/SPI.c
+++ b/ports/atmel-samd/common-hal/busio/SPI.c
@@ -89,8 +89,8 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
     Sercom* sercom = NULL;
     uint8_t sercom_index;
     uint32_t clock_pinmux = 0;
-    bool mosi_none = mosi == mp_const_none || mosi == NULL;
-    bool miso_none = miso == mp_const_none || miso == NULL;
+    bool mosi_none = mosi == NULL;
+    bool miso_none = miso == NULL;
     uint32_t mosi_pinmux = 0;
     uint32_t miso_pinmux = 0;
     uint8_t clock_pad = 0;
diff --git a/ports/atmel-samd/common-hal/busio/UART.c b/ports/atmel-samd/common-hal/busio/UART.c
index fb9968605f..1f6b75f972 100644
--- a/ports/atmel-samd/common-hal/busio/UART.c
+++ b/ports/atmel-samd/common-hal/busio/UART.c
@@ -65,7 +65,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     uint32_t tx_pinmux = 0;
     uint8_t tx_pad = 255; // Unset pad
 
-    if ((rts != mp_const_none) || (cts != mp_const_none) || (rs485_dir != mp_const_none) || (rs485_invert)) {
+    if ((rts != NULL) || (cts != NULL) || (rs485_dir != NULL) || (rs485_invert)) {
         mp_raise_ValueError(translate("RTS/CTS/RS485 Not yet supported on this device"));
     }
 
@@ -73,8 +73,8 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
         mp_raise_NotImplementedError(translate("bytes > 8 bits not supported"));
     }
 
-    bool have_tx = tx != mp_const_none;
-    bool have_rx = rx != mp_const_none;
+    bool have_tx = tx != NULL;
+    bool have_rx = rx != NULL;
     if (!have_tx && !have_rx) {
         mp_raise_ValueError(translate("tx and rx cannot both be None"));
     }
@@ -109,7 +109,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
 #endif
             tx_pinmux = PINMUX(tx->number, (i == 0) ? MUX_C : MUX_D);
             tx_pad = tx->sercom[i].pad;
-            if (rx == mp_const_none) {
+            if (rx == NULL) {
                 sercom = potential_sercom;
                 break;
             }
diff --git a/ports/atmel-samd/common-hal/digitalio/DigitalInOut.c b/ports/atmel-samd/common-hal/digitalio/DigitalInOut.c
index e167cbb694..68d3da806c 100644
--- a/ports/atmel-samd/common-hal/digitalio/DigitalInOut.c
+++ b/ports/atmel-samd/common-hal/digitalio/DigitalInOut.c
@@ -55,7 +55,7 @@ void common_hal_digitalio_digitalinout_never_reset(
 }
 
 bool common_hal_digitalio_digitalinout_deinited(digitalio_digitalinout_obj_t* self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_digitalio_digitalinout_deinit(digitalio_digitalinout_obj_t* self) {
@@ -63,7 +63,7 @@ void common_hal_digitalio_digitalinout_deinit(digitalio_digitalinout_obj_t* self
         return;
     }
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 void common_hal_digitalio_digitalinout_switch_to_input(
diff --git a/ports/atmel-samd/common-hal/pulseio/PWMOut.c b/ports/atmel-samd/common-hal/pulseio/PWMOut.c
index 0adb23fc5d..fef581584f 100644
--- a/ports/atmel-samd/common-hal/pulseio/PWMOut.c
+++ b/ports/atmel-samd/common-hal/pulseio/PWMOut.c
@@ -292,7 +292,7 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
 }
 
 bool common_hal_pulseio_pwmout_deinited(pulseio_pwmout_obj_t* self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_pulseio_pwmout_deinit(pulseio_pwmout_obj_t* self) {
@@ -319,7 +319,7 @@ void common_hal_pulseio_pwmout_deinit(pulseio_pwmout_obj_t* self) {
         }
     }
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 extern void common_hal_pulseio_pwmout_set_duty_cycle(pulseio_pwmout_obj_t* self, uint16_t duty) {
diff --git a/ports/cxd56/common-hal/analogio/AnalogIn.c b/ports/cxd56/common-hal/analogio/AnalogIn.c
index e2ca5e4a42..cdf37c06a7 100644
--- a/ports/cxd56/common-hal/analogio/AnalogIn.c
+++ b/ports/cxd56/common-hal/analogio/AnalogIn.c
@@ -83,7 +83,7 @@ void common_hal_analogio_analogin_construct(analogio_analogin_obj_t *self, const
 
     // start ADC
     ioctl(analogin_dev[self->number].fd, ANIOC_CXD56_START, 0);
-    
+
     self->pin = pin;
 }
 
@@ -97,7 +97,7 @@ void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
     close(analogin_dev[self->number].fd);
     analogin_dev[self->number].fd = -1;
 
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 bool common_hal_analogio_analogin_deinited(analogio_analogin_obj_t *self) {
diff --git a/ports/cxd56/common-hal/busio/UART.c b/ports/cxd56/common-hal/busio/UART.c
index 3ed9809529..3bca240e01 100644
--- a/ports/cxd56/common-hal/busio/UART.c
+++ b/ports/cxd56/common-hal/busio/UART.c
@@ -60,10 +60,10 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     mp_float_t timeout, uint16_t receiver_buffer_size) {
     struct termios tio;
 
-    if ((rts != mp_const_none) || (cts != mp_const_none) || (rs485_dir != mp_const_none) || (rs485_invert)) {
+    if ((rts != NULL) || (cts != NULL) || (rs485_dir != NULL) || (rs485_invert)) {
         mp_raise_ValueError(translate("RTS/CTS/RS485 Not yet supported on this device"));
     }
-    
+
     if (bits != 8) {
         mp_raise_ValueError(translate("Could not initialize UART"));
     }
diff --git a/ports/cxd56/common-hal/digitalio/DigitalInOut.c b/ports/cxd56/common-hal/digitalio/DigitalInOut.c
index 7b1f6cc031..c9af12e443 100644
--- a/ports/cxd56/common-hal/digitalio/DigitalInOut.c
+++ b/ports/cxd56/common-hal/digitalio/DigitalInOut.c
@@ -56,11 +56,11 @@ void common_hal_digitalio_digitalinout_deinit(digitalio_digitalinout_obj_t *self
     board_gpio_config(self->pin->number, 0, false, true, PIN_FLOAT);
 
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 bool common_hal_digitalio_digitalinout_deinited(digitalio_digitalinout_obj_t *self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_digitalio_digitalinout_switch_to_input(digitalio_digitalinout_obj_t *self, digitalio_pull_t pull) {
diff --git a/ports/cxd56/common-hal/pulseio/PWMOut.c b/ports/cxd56/common-hal/pulseio/PWMOut.c
index a0b4e79c60..7e0be566b4 100644
--- a/ports/cxd56/common-hal/pulseio/PWMOut.c
+++ b/ports/cxd56/common-hal/pulseio/PWMOut.c
@@ -50,7 +50,7 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t *self,
     const mcu_pin_obj_t *pin, uint16_t duty, uint32_t frequency,
     bool variable_frequency) {
     self->number = -1;
-    
+
     for (int i = 0; i < MP_ARRAY_SIZE(pwmout_dev); i++) {
         if (pin->number == pwmout_dev[i].pin->number) {
             self->number = i;
@@ -95,7 +95,7 @@ void common_hal_pulseio_pwmout_deinit(pulseio_pwmout_obj_t *self) {
     pwmout_dev[self->number].fd = -1;
 
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 bool common_hal_pulseio_pwmout_deinited(pulseio_pwmout_obj_t *self) {
@@ -131,11 +131,11 @@ bool common_hal_pulseio_pwmout_get_variable_frequency(pulseio_pwmout_obj_t *self
 void common_hal_pulseio_pwmout_never_reset(pulseio_pwmout_obj_t *self) {
     never_reset_pin_number(self->pin->number);
 
-    pwmout_dev[self->number].reset = false;    
+    pwmout_dev[self->number].reset = false;
 }
 
 void common_hal_pulseio_pwmout_reset_ok(pulseio_pwmout_obj_t *self) {
-    pwmout_dev[self->number].reset = true; 
+    pwmout_dev[self->number].reset = true;
 }
 
 void pwmout_reset(void) {
diff --git a/ports/cxd56/common-hal/pulseio/PulseIn.c b/ports/cxd56/common-hal/pulseio/PulseIn.c
index dd2773d1d0..65ca1d97eb 100644
--- a/ports/cxd56/common-hal/pulseio/PulseIn.c
+++ b/ports/cxd56/common-hal/pulseio/PulseIn.c
@@ -106,7 +106,7 @@ void common_hal_pulseio_pulsein_construct(pulseio_pulsein_obj_t *self,
 
     board_gpio_int(self->pin->number, true);
 }
-    
+
 void common_hal_pulseio_pulsein_deinit(pulseio_pulsein_obj_t *self) {
     if (common_hal_pulseio_pulsein_deinited(self)) {
         return;
@@ -116,18 +116,18 @@ void common_hal_pulseio_pulsein_deinit(pulseio_pulsein_obj_t *self) {
     board_gpio_intconfig(self->pin->number, 0, false, NULL);
 
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
- 
+
 bool common_hal_pulseio_pulsein_deinited(pulseio_pulsein_obj_t *self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
- 
+
 void common_hal_pulseio_pulsein_pause(pulseio_pulsein_obj_t *self) {
     board_gpio_int(self->pin->number, false);
     self->paused = true;
 }
- 
+
 void common_hal_pulseio_pulsein_resume(pulseio_pulsein_obj_t *self, uint16_t trigger_duration) {
     // Make sure we're paused.
     common_hal_pulseio_pulsein_pause(self);
@@ -147,14 +147,14 @@ void common_hal_pulseio_pulsein_resume(pulseio_pulsein_obj_t *self, uint16_t tri
     pulsein_set_config(self, true);
     board_gpio_int(self->pin->number, true);
 }
- 
+
 void common_hal_pulseio_pulsein_clear(pulseio_pulsein_obj_t *self) {
     common_hal_mcu_disable_interrupts();
     self->start = 0;
     self->len = 0;
     common_hal_mcu_enable_interrupts();
 }
- 
+
 uint16_t common_hal_pulseio_pulsein_popleft(pulseio_pulsein_obj_t *self) {
     if (self->len == 0) {
         mp_raise_IndexError(translate("pop from an empty PulseIn"));
@@ -167,19 +167,19 @@ uint16_t common_hal_pulseio_pulsein_popleft(pulseio_pulsein_obj_t *self) {
 
     return value;
 }
- 
+
 uint16_t common_hal_pulseio_pulsein_get_maxlen(pulseio_pulsein_obj_t *self) {
     return self->maxlen;
 }
- 
+
 bool common_hal_pulseio_pulsein_get_paused(pulseio_pulsein_obj_t *self) {
     return self->paused;
 }
- 
+
 uint16_t common_hal_pulseio_pulsein_get_len(pulseio_pulsein_obj_t *self) {
     return self->len;
 }
- 
+
 uint16_t common_hal_pulseio_pulsein_get_item(pulseio_pulsein_obj_t *self, int16_t index) {
     common_hal_mcu_disable_interrupts();
     if (index < 0) {
@@ -193,4 +193,3 @@ uint16_t common_hal_pulseio_pulsein_get_item(pulseio_pulsein_obj_t *self, int16_
     common_hal_mcu_enable_interrupts();
     return value;
 }
- 
\ No newline at end of file
diff --git a/ports/mimxrt10xx/common-hal/analogio/AnalogIn.c b/ports/mimxrt10xx/common-hal/analogio/AnalogIn.c
index d714001f33..2cc2681b44 100644
--- a/ports/mimxrt10xx/common-hal/analogio/AnalogIn.c
+++ b/ports/mimxrt10xx/common-hal/analogio/AnalogIn.c
@@ -58,7 +58,7 @@ void common_hal_analogio_analogin_construct(analogio_analogin_obj_t* self,
 }
 
 bool common_hal_analogio_analogin_deinited(analogio_analogin_obj_t *self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
@@ -66,7 +66,7 @@ void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
         return;
     }
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {
diff --git a/ports/mimxrt10xx/common-hal/busio/UART.c b/ports/mimxrt10xx/common-hal/busio/UART.c
index 4fd7afecbc..b34b948b29 100644
--- a/ports/mimxrt10xx/common-hal/busio/UART.c
+++ b/ports/mimxrt10xx/common-hal/busio/UART.c
@@ -80,8 +80,8 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
 
     // TODO: Allow none rx or tx
 
-    bool have_tx = tx != mp_const_none;
-    bool have_rx = rx != mp_const_none;
+    bool have_tx = tx != NULL;
+    bool have_rx = rx != NULL;
     if (!have_tx && !have_rx) {
         mp_raise_ValueError(translate("tx and rx cannot both be None"));
     }
@@ -116,8 +116,8 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     }
 
     // Filter for sane settings for RS485
-    if (rs485_dir != mp_const_none) {
-      if ((rts != mp_const_none) || (cts != mp_const_none)) {
+    if (rs485_dir != NULL) {
+      if ((rts != NULL) || (cts != NULL)) {
         mp_raise_ValueError(translate("Cannot specify RTS or CTS in RS485 mode"));
       }
       // For IMXRT the RTS pin is used for RS485 direction
@@ -133,7 +133,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     const uint32_t rts_count = sizeof(mcu_uart_rts_list) / sizeof(mcu_periph_obj_t);
     const uint32_t cts_count = sizeof(mcu_uart_cts_list) / sizeof(mcu_periph_obj_t);
 
-    if (rts != mp_const_none) {
+    if (rts != NULL) {
       for (uint32_t i=0; i < rts_count; ++i) {
         if (mcu_uart_rts_list[i].bank_idx == self->rx_pin->bank_idx) {
           if (mcu_uart_rts_list[i].pin == rts) {
@@ -146,7 +146,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
         mp_raise_ValueError(translate("Selected RTS pin not valid"));
     }
 
-    if (cts != mp_const_none) {
+    if (cts != NULL) {
       for (uint32_t i=0; i < cts_count; ++i) {
         if (mcu_uart_cts_list[i].bank_idx == self->rx_pin->bank_idx) {
           if (mcu_uart_cts_list[i].pin == cts) {
@@ -158,7 +158,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
       if (self->cts_pin == NULL)
         mp_raise_ValueError(translate("Selected CTS pin not valid"));
     }
-    
+
     self->uart = mcu_uart_banks[self->tx_pin->bank_idx - 1];
 
     config_periph_pin(self->rx_pin);
@@ -166,7 +166,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     if (self->rts_pin)
       config_periph_pin(self->rts_pin);
     if (self->cts_pin)
-      config_periph_pin(self->cts_pin);    
+      config_periph_pin(self->cts_pin);
 
     lpuart_config_t config = { 0 };
     LPUART_GetDefaultConfig(&config);
@@ -187,7 +187,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     // Before we init, setup RS485 direction pin
     // ..unfortunately this isn't done by the driver library
     uint32_t modir = (self->uart->MODIR) & ~(LPUART_MODIR_TXRTSPOL_MASK | LPUART_MODIR_TXRTSE_MASK);
-    if (rs485_dir != mp_const_none) {
+    if (rs485_dir != NULL) {
       modir |= LPUART_MODIR_TXRTSE_MASK;
       if (rs485_invert)
         modir |= LPUART_MODIR_TXRTSPOL_MASK;
diff --git a/ports/mimxrt10xx/common-hal/digitalio/DigitalInOut.c b/ports/mimxrt10xx/common-hal/digitalio/DigitalInOut.c
index d69a18d962..603515764f 100644
--- a/ports/mimxrt10xx/common-hal/digitalio/DigitalInOut.c
+++ b/ports/mimxrt10xx/common-hal/digitalio/DigitalInOut.c
@@ -78,7 +78,7 @@ void common_hal_digitalio_digitalinout_never_reset(
 }
 
 bool common_hal_digitalio_digitalinout_deinited(digitalio_digitalinout_obj_t* self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_digitalio_digitalinout_deinit(digitalio_digitalinout_obj_t* self) {
@@ -86,7 +86,7 @@ void common_hal_digitalio_digitalinout_deinit(digitalio_digitalinout_obj_t* self
         return;
     }
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 void common_hal_digitalio_digitalinout_switch_to_input(
diff --git a/ports/nrf/boards/clue_nrf52840_express/board.c b/ports/nrf/boards/clue_nrf52840_express/board.c
index 5f5337a3da..e342c6d939 100644
--- a/ports/nrf/boards/clue_nrf52840_express/board.c
+++ b/ports/nrf/boards/clue_nrf52840_express/board.c
@@ -49,7 +49,7 @@ uint8_t display_init_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_P0_14, &pin_P0_15, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_P0_14, &pin_P0_15, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/nrf/boards/ohs2020_badge/board.c b/ports/nrf/boards/ohs2020_badge/board.c
index 7e3e058144..9e881d7639 100644
--- a/ports/nrf/boards/ohs2020_badge/board.c
+++ b/ports/nrf/boards/ohs2020_badge/board.c
@@ -49,7 +49,7 @@ uint8_t display_init_sequence[] = {
 
 void board_init(void) {
     busio_spi_obj_t* spi = &displays[0].fourwire_bus.inline_bus;
-    common_hal_busio_spi_construct(spi, &pin_P0_11, &pin_P0_12, mp_const_none);
+    common_hal_busio_spi_construct(spi, &pin_P0_11, &pin_P0_12, NULL);
     common_hal_busio_spi_never_reset(spi);
 
     displayio_fourwire_obj_t* bus = &displays[0].fourwire_bus;
diff --git a/ports/nrf/common-hal/analogio/AnalogIn.c b/ports/nrf/common-hal/analogio/AnalogIn.c
index 3bc097019e..dbcc5281ce 100644
--- a/ports/nrf/common-hal/analogio/AnalogIn.c
+++ b/ports/nrf/common-hal/analogio/AnalogIn.c
@@ -55,7 +55,7 @@ void common_hal_analogio_analogin_construct(analogio_analogin_obj_t *self, const
 }
 
 bool common_hal_analogio_analogin_deinited(analogio_analogin_obj_t *self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
@@ -65,7 +65,7 @@ void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
     nrf_gpio_cfg_default(self->pin->number);
 
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {
diff --git a/ports/nrf/common-hal/busio/SPI.c b/ports/nrf/common-hal/busio/SPI.c
index b4ebddde1d..3f205e7782 100644
--- a/ports/nrf/common-hal/busio/SPI.c
+++ b/ports/nrf/common-hal/busio/SPI.c
@@ -155,7 +155,7 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self, const mcu_pin_obj_t *
     self->clock_pin_number = clock->number;
     claim_pin(clock);
 
-    if (mosi != mp_const_none) {
+    if (mosi != NULL) {
         config.mosi_pin = mosi->number;
         self->MOSI_pin_number = mosi->number;
         claim_pin(mosi);
@@ -163,7 +163,7 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self, const mcu_pin_obj_t *
         self->MOSI_pin_number = NO_PIN;
     }
 
-    if (miso != mp_const_none) {
+    if (miso != NULL) {
         config.miso_pin = miso->number;
         self->MISO_pin_number = mosi->number;
         claim_pin(miso);
diff --git a/ports/nrf/common-hal/busio/UART.c b/ports/nrf/common-hal/busio/UART.c
index 933faf17b8..14fa363749 100644
--- a/ports/nrf/common-hal/busio/UART.c
+++ b/ports/nrf/common-hal/busio/UART.c
@@ -135,10 +135,10 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     uint32_t baudrate, uint8_t bits, uart_parity_t parity, uint8_t stop,
     mp_float_t timeout, uint16_t receiver_buffer_size) {
 
-    if ((rts != mp_const_none) || (cts != mp_const_none) || (rs485_dir != mp_const_none) || (rs485_invert)) {
+    if ((rts != NULL) || (cts != NULL) || (rs485_dir != NULL) || (rs485_invert)) {
         mp_raise_ValueError(translate("RTS/CTS/RS485 Not yet supported on this device"));
     }
-  
+
     // Find a free UART peripheral.
     self->uarte = NULL;
     for (size_t i = 0 ; i < MP_ARRAY_SIZE(nrfx_uartes); i++) {
@@ -152,7 +152,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
         mp_raise_ValueError(translate("All UART peripherals are in use"));
     }
 
-    if ( (tx == mp_const_none) && (rx == mp_const_none) ) {
+    if ( (tx == NULL) && (rx == NULL) ) {
         mp_raise_ValueError(translate("tx and rx cannot both be None"));
     }
 
@@ -165,8 +165,8 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     }
 
     nrfx_uarte_config_t config = {
-        .pseltxd = (tx == mp_const_none) ? NRF_UARTE_PSEL_DISCONNECTED : tx->number,
-        .pselrxd = (rx == mp_const_none) ? NRF_UARTE_PSEL_DISCONNECTED : rx->number,
+        .pseltxd = (tx == NULL) ? NRF_UARTE_PSEL_DISCONNECTED : tx->number,
+        .pselrxd = (rx == NULL) ? NRF_UARTE_PSEL_DISCONNECTED : rx->number,
         .pselcts = NRF_UARTE_PSEL_DISCONNECTED,
         .pselrts = NRF_UARTE_PSEL_DISCONNECTED,
         .p_context = self,
@@ -181,7 +181,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     _VERIFY_ERR(nrfx_uarte_init(self->uarte, &config, uart_callback_irq));
 
     // Init buffer for rx
-    if ( rx != mp_const_none ) {
+    if ( rx != NULL ) {
         // Initially allocate the UART's buffer in the long-lived part of the
         // heap.  UARTs are generally long-lived objects, but the "make long-
         // lived" machinery is incapable of moving internal pointers like
@@ -200,7 +200,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
         claim_pin(rx);
     }
 
-    if ( tx != mp_const_none ) {
+    if ( tx != NULL ) {
         self->tx_pin_number = tx->number;
         claim_pin(tx);
     } else {
diff --git a/ports/nrf/common-hal/digitalio/DigitalInOut.c b/ports/nrf/common-hal/digitalio/DigitalInOut.c
index 0836962c63..c5a7a7dfba 100644
--- a/ports/nrf/common-hal/digitalio/DigitalInOut.c
+++ b/ports/nrf/common-hal/digitalio/DigitalInOut.c
@@ -46,7 +46,7 @@ digitalinout_result_t common_hal_digitalio_digitalinout_construct(
 }
 
 bool common_hal_digitalio_digitalinout_deinited(digitalio_digitalinout_obj_t *self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_digitalio_digitalinout_deinit(digitalio_digitalinout_obj_t *self) {
@@ -56,7 +56,7 @@ void common_hal_digitalio_digitalinout_deinit(digitalio_digitalinout_obj_t *self
     nrf_gpio_cfg_default(self->pin->number);
 
     reset_pin_number(self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 void common_hal_digitalio_digitalinout_switch_to_input(
diff --git a/ports/stm32f4/common-hal/analogio/AnalogIn.c b/ports/stm32f4/common-hal/analogio/AnalogIn.c
index 3ee3c4dbbb..1d1b308b66 100644
--- a/ports/stm32f4/common-hal/analogio/AnalogIn.c
+++ b/ports/stm32f4/common-hal/analogio/AnalogIn.c
@@ -45,11 +45,11 @@ void common_hal_analogio_analogin_construct(analogio_analogin_obj_t* self,
     }
     // TODO: add ADC traits to structure?
 
-    // Note that ADC2 is always bundled pin-to-pin with ADC1 if it exists, and used only 
-    // for dual conversion. For this basic application it is never used. 
+    // Note that ADC2 is always bundled pin-to-pin with ADC1 if it exists, and used only
+    // for dual conversion. For this basic application it is never used.
     LL_GPIO_SetPinMode(pin_port(pin->port), (uint32_t)pin_mask(pin->number), LL_GPIO_MODE_ANALOG);
     if (pin->adc_unit & 0x01) {
-        LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_ADC1); 
+        LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_ADC1);
     } else if (pin->adc_unit == 0x04) {
         #ifdef LL_APB2_GRP1_PERIPH_ADC3
         LL_APB2_GRP1_EnableClock(LL_APB2_GRP1_PERIPH_ADC3);
@@ -62,7 +62,7 @@ void common_hal_analogio_analogin_construct(analogio_analogin_obj_t* self,
 }
 
 bool common_hal_analogio_analogin_deinited(analogio_analogin_obj_t *self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
@@ -70,7 +70,7 @@ void common_hal_analogio_analogin_deinit(analogio_analogin_obj_t *self) {
         return;
     }
     reset_pin_number(self->pin->port,self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {
@@ -116,10 +116,10 @@ uint16_t common_hal_analogio_analogin_get_value(analogio_analogin_obj_t *self) {
     HAL_ADC_ConfigChannel(&AdcHandle, &sConfig);
 
     HAL_ADC_Start(&AdcHandle);
-    HAL_ADC_PollForConversion(&AdcHandle,1); 
+    HAL_ADC_PollForConversion(&AdcHandle,1);
     uint16_t value = (uint16_t)HAL_ADC_GetValue(&AdcHandle);
     HAL_ADC_Stop(&AdcHandle);
-    
+
     // // Shift the value to be 16 bit.
     return value << 4;
 }
diff --git a/ports/stm32f4/common-hal/analogio/AnalogOut.c b/ports/stm32f4/common-hal/analogio/AnalogOut.c
index 79ced0492f..2ea969f503 100644
--- a/ports/stm32f4/common-hal/analogio/AnalogOut.c
+++ b/ports/stm32f4/common-hal/analogio/AnalogOut.c
@@ -39,7 +39,7 @@
 
 #include "stm32f4xx_hal.h"
 
-//DAC is shared between both channels. 
+//DAC is shared between both channels.
 #if HAS_DAC
 DAC_HandleTypeDef handle;
 #endif
@@ -97,7 +97,7 @@ bool common_hal_analogio_analogout_deinited(analogio_analogout_obj_t *self) {
 void common_hal_analogio_analogout_deinit(analogio_analogout_obj_t *self) {
     #if HAS_DAC
     reset_pin_number(self->pin->port,self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
     dac_on[self->dac_index] = false;
 
     //turn off the DAC if both channels are off
diff --git a/ports/stm32f4/common-hal/busio/I2C.c b/ports/stm32f4/common-hal/busio/I2C.c
index 1437e5e784..8e98b966d2 100644
--- a/ports/stm32f4/common-hal/busio/I2C.c
+++ b/ports/stm32f4/common-hal/busio/I2C.c
@@ -100,14 +100,14 @@ void common_hal_busio_i2c_construct(busio_i2c_obj_t *self,
     GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
     GPIO_InitStruct.Pull = GPIO_PULLUP;
     GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
-    GPIO_InitStruct.Alternate = self->sda->altfn_index; 
+    GPIO_InitStruct.Alternate = self->sda->altfn_index;
     HAL_GPIO_Init(pin_port(sda->port), &GPIO_InitStruct);
 
     GPIO_InitStruct.Pin = pin_mask(scl->number);
     GPIO_InitStruct.Mode = GPIO_MODE_AF_OD;
     GPIO_InitStruct.Pull = GPIO_PULLUP;
     GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
-    GPIO_InitStruct.Alternate = self->scl->altfn_index; 
+    GPIO_InitStruct.Alternate = self->scl->altfn_index;
     HAL_GPIO_Init(pin_port(scl->port), &GPIO_InitStruct);
 
     //Note: due to I2C soft reboot issue, do not relocate clock init.
@@ -144,7 +144,7 @@ void common_hal_busio_i2c_never_reset(busio_i2c_obj_t *self) {
 }
 
 bool common_hal_busio_i2c_deinited(busio_i2c_obj_t *self) {
-    return self->sda->pin == mp_const_none;
+    return self->sda == NULL;
 }
 
 void common_hal_busio_i2c_deinit(busio_i2c_obj_t *self) {
@@ -158,8 +158,8 @@ void common_hal_busio_i2c_deinit(busio_i2c_obj_t *self) {
 
     reset_pin_number(self->sda->pin->port,self->sda->pin->number);
     reset_pin_number(self->scl->pin->port,self->scl->pin->number);
-    self->sda = mp_const_none;
-    self->scl = mp_const_none;
+    self->sda = NULL;
+    self->scl = NULL;
 }
 
 bool common_hal_busio_i2c_probe(busio_i2c_obj_t *self, uint8_t addr) {
@@ -169,7 +169,7 @@ bool common_hal_busio_i2c_probe(busio_i2c_obj_t *self, uint8_t addr) {
 bool common_hal_busio_i2c_try_lock(busio_i2c_obj_t *self) {
     bool grabbed_lock = false;
 
-    //Critical section code that may be required at some point. 
+    //Critical section code that may be required at some point.
     // uint32_t store_primask = __get_PRIMASK();
     // __disable_irq();
     // __DMB();
@@ -195,19 +195,19 @@ void common_hal_busio_i2c_unlock(busio_i2c_obj_t *self) {
 
 uint8_t common_hal_busio_i2c_write(busio_i2c_obj_t *self, uint16_t addr,
                                    const uint8_t *data, size_t len, bool transmit_stop_bit) {
-    HAL_StatusTypeDef result = HAL_I2C_Master_Transmit(&(self->handle), (uint16_t)(addr << 1), 
+    HAL_StatusTypeDef result = HAL_I2C_Master_Transmit(&(self->handle), (uint16_t)(addr << 1),
                                                         (uint8_t *)data, (uint16_t)len, 500);
     return result == HAL_OK ? 0 : MP_EIO;
 }
 
 uint8_t common_hal_busio_i2c_read(busio_i2c_obj_t *self, uint16_t addr,
         uint8_t *data, size_t len) {
-    return HAL_I2C_Master_Receive(&(self->handle), (uint16_t)(addr<<1), data, (uint16_t)len, 500) 
+    return HAL_I2C_Master_Receive(&(self->handle), (uint16_t)(addr<<1), data, (uint16_t)len, 500)
                                     == HAL_OK ? 0 : MP_EIO;
 }
 
 STATIC void i2c_clock_enable(uint8_t mask) {
-    //Note: hard reset required due to soft reboot issue. 
+    //Note: hard reset required due to soft reboot issue.
     #ifdef I2C1
     if (mask & (1 << 0)) {
         __HAL_RCC_I2C1_CLK_ENABLE();
diff --git a/ports/stm32f4/common-hal/busio/SPI.c b/ports/stm32f4/common-hal/busio/SPI.c
index e00b5e9f0c..7e25e0a571 100644
--- a/ports/stm32f4/common-hal/busio/SPI.c
+++ b/ports/stm32f4/common-hal/busio/SPI.c
@@ -49,7 +49,7 @@ STATIC void spi_clock_enable(uint8_t mask);
 STATIC void spi_clock_disable(uint8_t mask);
 
 STATIC uint32_t get_busclock(SPI_TypeDef * instance) {
-    //SPI2 and 3 are on PCLK1, if they exist. 
+    //SPI2 and 3 are on PCLK1, if they exist.
     #ifdef SPI2
         if (instance == SPI2) return HAL_RCC_GetPCLK1Freq();
     #endif
@@ -113,7 +113,7 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
     for (uint i = 0; i < sck_len; i++) {
         if (mcu_spi_sck_list[i].pin == sck) {
             //if both MOSI and MISO exist, loop search normally
-            if ((mosi != mp_const_none) && (miso != mp_const_none)) {
+            if ((mosi != NULL) && (miso != NULL)) {
                 //MOSI
                 for (uint j = 0; j < mosi_len; j++) {
                     if (mcu_spi_mosi_list[j].pin == mosi) {
@@ -133,11 +133,11 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
                                 self->miso = &mcu_spi_miso_list[k];
                                 break;
                             }
-                        }   
+                        }
                     }
                 }
             // if just MISO, reduce search
-            } else if (miso != mp_const_none) {
+            } else if (miso != NULL) {
                 for (uint j = 0; j < miso_len; j++) {
                     if ((mcu_spi_miso_list[j].pin == miso) //only SCK and MISO need the same index
                         && (mcu_spi_sck_list[i].spi_index == mcu_spi_miso_list[j].spi_index)) {
@@ -152,9 +152,9 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
                         self->miso = &mcu_spi_miso_list[j];
                         break;
                     }
-                }  
+                }
             // if just MOSI, reduce search
-            } else if (mosi != mp_const_none) {
+            } else if (mosi != NULL) {
                 for (uint j = 0; j < mosi_len; j++) {
                     if ((mcu_spi_mosi_list[j].pin == mosi) //only SCK and MOSI need the same index
                         && (mcu_spi_sck_list[i].spi_index == mcu_spi_mosi_list[j].spi_index)) {
@@ -169,7 +169,7 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
                         self->miso = NULL;
                         break;
                     }
-                }  
+                }
             } else {
                 //throw an error immediately
                 mp_raise_ValueError(translate("Must provide MISO or MOSI pin"));
@@ -179,8 +179,8 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
 
     //handle typedef selection, errors
     if ( (self->sck != NULL && self->mosi != NULL && self->miso != NULL) ||
-        (self->sck != NULL && self->mosi != NULL && miso == mp_const_none) ||
-        (self->sck != NULL && self->miso != NULL && mosi == mp_const_none)) {
+        (self->sck != NULL && self->mosi != NULL && miso == NULL) ||
+        (self->sck != NULL && self->miso != NULL && mosi == NULL)) {
         SPIx = mcu_spi_banks[self->sck->spi_index - 1];
     } else {
         if (spi_taken) {
@@ -196,7 +196,7 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
     GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
     GPIO_InitStruct.Pull = GPIO_NOPULL;
     GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
-    GPIO_InitStruct.Alternate = self->sck->altfn_index; 
+    GPIO_InitStruct.Alternate = self->sck->altfn_index;
     HAL_GPIO_Init(pin_port(sck->port), &GPIO_InitStruct);
 
     if (self->mosi != NULL) {
@@ -204,7 +204,7 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
         GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
         GPIO_InitStruct.Pull = GPIO_NOPULL;
         GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
-        GPIO_InitStruct.Alternate = self->mosi->altfn_index; 
+        GPIO_InitStruct.Alternate = self->mosi->altfn_index;
         HAL_GPIO_Init(pin_port(mosi->port), &GPIO_InitStruct);
     }
 
@@ -213,14 +213,14 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
         GPIO_InitStruct.Mode = GPIO_MODE_AF_PP;
         GPIO_InitStruct.Pull = GPIO_NOPULL;
         GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
-        GPIO_InitStruct.Alternate = self->miso->altfn_index; 
+        GPIO_InitStruct.Alternate = self->miso->altfn_index;
         HAL_GPIO_Init(pin_port(miso->port), &GPIO_InitStruct);
     }
 
     spi_clock_enable(1 << (self->sck->spi_index - 1));
     reserved_spi[self->sck->spi_index - 1] = true;
-    
-    self->handle.Instance = SPIx; 
+
+    self->handle.Instance = SPIx;
     self->handle.Init.Mode = SPI_MODE_MASTER;
     // Direction change only required for RX-only, see RefMan RM0090:884
     self->handle.Init.Direction = (self->mosi == NULL) ? SPI_CR1_RXONLY : SPI_DIRECTION_2LINES;
@@ -269,7 +269,7 @@ void common_hal_busio_spi_never_reset(busio_spi_obj_t *self) {
 }
 
 bool common_hal_busio_spi_deinited(busio_spi_obj_t *self) {
-    return self->sck->pin == mp_const_none;
+    return self->sck->pin == NULL;
 }
 
 void common_hal_busio_spi_deinit(busio_spi_obj_t *self) {
@@ -287,15 +287,15 @@ void common_hal_busio_spi_deinit(busio_spi_obj_t *self) {
     if (self->miso != NULL) {
         reset_pin_number(self->miso->pin->port,self->miso->pin->number);
     }
-    self->sck = mp_const_none;
-    self->mosi = mp_const_none;
-    self->miso = mp_const_none;
+    self->sck = NULL;
+    self->mosi = NULL;
+    self->miso = NULL;
 }
 
 bool common_hal_busio_spi_configure(busio_spi_obj_t *self,
         uint32_t baudrate, uint8_t polarity, uint8_t phase, uint8_t bits) {
     //This resets the SPI, so check before updating it redundantly
-    if (baudrate == self->baudrate && polarity== self->polarity 
+    if (baudrate == self->baudrate && polarity== self->polarity
         && phase == self->phase && bits == self->bits) {
         return true;
     }
@@ -307,7 +307,7 @@ bool common_hal_busio_spi_configure(busio_spi_obj_t *self,
     self->handle.Init.CLKPolarity = (polarity) ? SPI_POLARITY_HIGH : SPI_POLARITY_LOW;
     self->handle.Init.CLKPhase = (phase) ? SPI_PHASE_2EDGE : SPI_PHASE_1EDGE;
 
-    self->handle.Init.BaudRatePrescaler = stm32_baud_to_spi_div(baudrate, &self->prescaler, 
+    self->handle.Init.BaudRatePrescaler = stm32_baud_to_spi_div(baudrate, &self->prescaler,
                                             get_busclock(self->handle.Instance));
 
     if (HAL_SPI_Init(&self->handle) != HAL_OK)
@@ -325,7 +325,7 @@ bool common_hal_busio_spi_configure(busio_spi_obj_t *self,
 bool common_hal_busio_spi_try_lock(busio_spi_obj_t *self) {
     bool grabbed_lock = false;
 
-    //Critical section code that may be required at some point. 
+    //Critical section code that may be required at some point.
     // uint32_t store_primask = __get_PRIMASK();
     // __disable_irq();
     // __DMB();
@@ -367,7 +367,7 @@ bool common_hal_busio_spi_read(busio_spi_obj_t *self,
     return result == HAL_OK;
 }
 
-bool common_hal_busio_spi_transfer(busio_spi_obj_t *self, 
+bool common_hal_busio_spi_transfer(busio_spi_obj_t *self,
         uint8_t *data_out, uint8_t *data_in, size_t len) {
     if (self->miso == NULL || self->mosi == NULL) {
         mp_raise_ValueError(translate("Missing MISO or MOSI Pin"));
diff --git a/ports/stm32f4/common-hal/busio/UART.c b/ports/stm32f4/common-hal/busio/UART.c
index 3c19092591..0b434fd023 100644
--- a/ports/stm32f4/common-hal/busio/UART.c
+++ b/ports/stm32f4/common-hal/busio/UART.c
@@ -86,12 +86,12 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
     bool uart_taken = false;
     uint8_t uart_index = 0; //origin 0 corrected
 
-    if ((rts != mp_const_none) || (cts != mp_const_none) || (rs485_dir != mp_const_none) || (rs485_invert == true)) {
+    if ((rts != NULL) || (cts != NULL) || (rs485_dir != NULL) || (rs485_invert == true)) {
         mp_raise_ValueError(translate("RTS/CTS/RS485 Not yet supported on this device"));
     }
-    
+
     //Can have both pins, or either
-    if ((tx != mp_const_none) && (rx != mp_const_none)) {
+    if ((tx != NULL) && (rx != NULL)) {
         //normal find loop if both pins exist
         for (uint i = 0; i < tx_len; i++) {
             if (mcu_uart_tx_list[i].pin == tx) {
@@ -115,7 +115,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
         uart_index = self->tx->uart_index - 1;
         USARTx = assign_uart_or_throw(self, (self->tx != NULL && self->rx != NULL),
             uart_index, uart_taken);
-    } else if (tx == mp_const_none) {
+    } else if (tx == NULL) {
         //If there is no tx, run only rx
         for (uint i = 0; i < rx_len; i++) {
             if (mcu_uart_rx_list[i].pin == rx) {
@@ -132,7 +132,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
         uart_index = self->rx->uart_index - 1;
         USARTx = assign_uart_or_throw(self, (self->rx != NULL),
             uart_index, uart_taken);
-    } else if (rx == mp_const_none) {
+    } else if (rx == NULL) {
         //If there is no rx, run only tx
         for (uint i = 0; i < tx_len; i++) {
             if (mcu_uart_tx_list[i].pin == tx) {
@@ -236,7 +236,7 @@ void common_hal_busio_uart_construct(busio_uart_obj_t *self,
 }
 
 bool common_hal_busio_uart_deinited(busio_uart_obj_t *self) {
-    return self->tx->pin == mp_const_none;
+    return self->tx->pin == NULL;
 }
 
 void common_hal_busio_uart_deinit(busio_uart_obj_t *self) {
@@ -244,8 +244,8 @@ void common_hal_busio_uart_deinit(busio_uart_obj_t *self) {
 
     reset_pin_number(self->tx->pin->port,self->tx->pin->number);
     reset_pin_number(self->rx->pin->port,self->rx->pin->number);
-    self->tx = mp_const_none;
-    self->rx = mp_const_none;
+    self->tx = NULL;
+    self->rx = NULL;
     gc_free(self->rbuf.buf);
     self->rbuf.size = 0;
     self->rbuf.iput = self->rbuf.iget = 0;
diff --git a/ports/stm32f4/common-hal/digitalio/DigitalInOut.c b/ports/stm32f4/common-hal/digitalio/DigitalInOut.c
index 36c1075e23..be2db4dace 100644
--- a/ports/stm32f4/common-hal/digitalio/DigitalInOut.c
+++ b/ports/stm32f4/common-hal/digitalio/DigitalInOut.c
@@ -54,7 +54,7 @@ digitalinout_result_t common_hal_digitalio_digitalinout_construct(
 }
 
 bool common_hal_digitalio_digitalinout_deinited(digitalio_digitalinout_obj_t *self) {
-    return self->pin == mp_const_none;
+    return self->pin == NULL;
 }
 
 void common_hal_digitalio_digitalinout_deinit(digitalio_digitalinout_obj_t *self) {
@@ -63,7 +63,7 @@ void common_hal_digitalio_digitalinout_deinit(digitalio_digitalinout_obj_t *self
     }
 
     reset_pin_number(self->pin->port, self->pin->number);
-    self->pin = mp_const_none;
+    self->pin = NULL;
 }
 
 void common_hal_digitalio_digitalinout_switch_to_input(
@@ -90,7 +90,7 @@ void common_hal_digitalio_digitalinout_switch_to_output(
 digitalio_direction_t common_hal_digitalio_digitalinout_get_direction(
         digitalio_digitalinout_obj_t *self) {
 
-    return (LL_GPIO_GetPinMode(pin_port(self->pin->port), pin_mask(self->pin->number)) 
+    return (LL_GPIO_GetPinMode(pin_port(self->pin->port), pin_mask(self->pin->number))
         == LL_GPIO_MODE_INPUT) ? DIRECTION_INPUT : DIRECTION_OUTPUT;
 }
 
@@ -111,7 +111,7 @@ void common_hal_digitalio_digitalinout_set_drive_mode(
         digitalio_drive_mode_t drive_mode) {
     GPIO_InitTypeDef GPIO_InitStruct = {0};
     GPIO_InitStruct.Pin = pin_mask(self->pin->number);
-    GPIO_InitStruct.Mode = (drive_mode == DRIVE_MODE_OPEN_DRAIN ? 
+    GPIO_InitStruct.Mode = (drive_mode == DRIVE_MODE_OPEN_DRAIN ?
         GPIO_MODE_OUTPUT_OD : GPIO_MODE_OUTPUT_PP);
     GPIO_InitStruct.Pull = GPIO_NOPULL;
     GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
@@ -121,7 +121,7 @@ void common_hal_digitalio_digitalinout_set_drive_mode(
 digitalio_drive_mode_t common_hal_digitalio_digitalinout_get_drive_mode(
         digitalio_digitalinout_obj_t *self) {
 
-    return LL_GPIO_GetPinOutputType(pin_port(self->pin->port), pin_mask(self->pin->number)) 
+    return LL_GPIO_GetPinOutputType(pin_port(self->pin->port), pin_mask(self->pin->number))
         == LL_GPIO_OUTPUT_OPENDRAIN ? DRIVE_MODE_OPEN_DRAIN : DRIVE_MODE_PUSH_PULL;
 }
 
@@ -145,7 +145,7 @@ void common_hal_digitalio_digitalinout_set_pull(
 
 digitalio_pull_t common_hal_digitalio_digitalinout_get_pull(
         digitalio_digitalinout_obj_t *self) {
-    
+
 
     switch (LL_GPIO_GetPinPull(pin_port(self->pin->port), pin_mask(self->pin->number))) {
         case LL_GPIO_PULL_UP:
diff --git a/ports/stm32f4/common-hal/pulseio/PWMOut.c b/ports/stm32f4/common-hal/pulseio/PWMOut.c
index 50bacbb514..c23fa74625 100644
--- a/ports/stm32f4/common-hal/pulseio/PWMOut.c
+++ b/ports/stm32f4/common-hal/pulseio/PWMOut.c
@@ -72,7 +72,7 @@ STATIC uint32_t timer_get_internal_duty(uint16_t duty, uint32_t period) {
     return (duty*period) / ((1 << 16) - 1);
 }
 
-STATIC void timer_get_optimal_divisors(uint32_t*period, uint32_t*prescaler, 
+STATIC void timer_get_optimal_divisors(uint32_t*period, uint32_t*prescaler,
                                        uint32_t frequency, uint32_t source_freq) {
     //Find the largest possible period supported by this frequency
     for (int i = 0; i < (1 << 16); i++) {
@@ -139,7 +139,7 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
                 first_time_setup = false; //skip setting up the timer
             }
             //No problems taken, so set it up
-            self->tim = l_tim; 
+            self->tim = l_tim;
             break;
         }
     }
@@ -182,7 +182,7 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
 
     uint32_t prescaler = 0; //prescaler is 15 bit
     uint32_t period = 0; //period is 16 bit
-    timer_get_optimal_divisors(&period, &prescaler, frequency, 
+    timer_get_optimal_divisors(&period, &prescaler, frequency,
                             timer_get_source_freq(self->tim->tim_index));
 
     //Timer init
@@ -240,7 +240,7 @@ void common_hal_pulseio_pwmout_reset_ok(pulseio_pwmout_obj_t *self) {
 }
 
 bool common_hal_pulseio_pwmout_deinited(pulseio_pwmout_obj_t* self) {
-    return self->tim == mp_const_none;
+    return self->tim == NULL;
 }
 
 void common_hal_pulseio_pwmout_deinit(pulseio_pwmout_obj_t* self) {
@@ -255,7 +255,7 @@ void common_hal_pulseio_pwmout_deinit(pulseio_pwmout_obj_t* self) {
         HAL_TIM_PWM_Stop(&self->handle, self->channel);
     }
     reset_pin_number(self->tim->pin->port,self->tim->pin->number);
-    self->tim = mp_const_none;
+    self->tim = NULL;
 
     //if reserved timer has no active channels, we can disable it
     if (!reserved_tim[self->tim->tim_index - 1]) {
@@ -276,13 +276,13 @@ uint16_t common_hal_pulseio_pwmout_get_duty_cycle(pulseio_pwmout_obj_t* self) {
 
 void common_hal_pulseio_pwmout_set_frequency(pulseio_pwmout_obj_t* self, uint32_t frequency) {
     //don't halt setup for the same frequency
-    if (frequency == self->frequency) { 
+    if (frequency == self->frequency) {
         return;
     }
 
     uint32_t prescaler = 0;
     uint32_t period = 0;
-    timer_get_optimal_divisors(&period, &prescaler, frequency, 
+    timer_get_optimal_divisors(&period, &prescaler, frequency,
                                 timer_get_source_freq(self->tim->tim_index));
 
     //shut down
@@ -290,7 +290,7 @@ void common_hal_pulseio_pwmout_set_frequency(pulseio_pwmout_obj_t* self, uint32_
 
     //Only change altered values
     self->handle.Init.Period = period - 1;
-    self->handle.Init.Prescaler = prescaler - 1; 
+    self->handle.Init.Prescaler = prescaler - 1;
 
     //restart everything, adjusting for new speed
     if (HAL_TIM_PWM_Init(&self->handle) != HAL_OK) {
diff --git a/shared-bindings/analogio/AnalogIn.c b/shared-bindings/analogio/AnalogIn.c
index 9a9b525d8b..9d1312dd86 100644
--- a/shared-bindings/analogio/AnalogIn.c
+++ b/shared-bindings/analogio/AnalogIn.c
@@ -63,16 +63,13 @@ STATIC mp_obj_t analogio_analogin_make_new(const mp_obj_type_t *type,
     mp_arg_check_num(n_args, kw_args, 1, 1, false);
 
     // 1st argument is the pin
-    mp_obj_t pin_obj = args[0];
-    assert_pin(pin_obj, false);
+    const mcu_pin_obj_t *pin = validate_is_free_pin(args[0]);
 
     analogio_analogin_obj_t *self = m_new_obj(analogio_analogin_obj_t);
     self->base.type = &analogio_analogin_type;
-    const mcu_pin_obj_t *pin = MP_OBJ_TO_PTR(pin_obj);
-    assert_pin_free(pin);
     common_hal_analogio_analogin_construct(self, pin);
 
-    return (mp_obj_t) self;
+    return MP_OBJ_FROM_PTR(self);
 }
 
 //|   .. method:: deinit()
@@ -141,7 +138,7 @@ STATIC mp_obj_t analogio_analogin_obj_get_reference_voltage(mp_obj_t self_in) {
 
     float reference_voltage = common_hal_analogio_analogin_get_reference_voltage(self);
     if (reference_voltage <= 0.0f) {
-        return mp_const_none; 
+        return mp_const_none;
     } else {
         return mp_obj_new_float(reference_voltage);
     }
diff --git a/shared-bindings/analogio/AnalogOut.c b/shared-bindings/analogio/AnalogOut.c
index 0816da4657..2496f17849 100644
--- a/shared-bindings/analogio/AnalogOut.c
+++ b/shared-bindings/analogio/AnalogOut.c
@@ -62,15 +62,13 @@ STATIC mp_obj_t analogio_analogout_make_new(const mp_obj_type_t *type, mp_uint_t
     // check arguments
     mp_arg_check_num(n_args, kw_args, 1, 1, false);
 
-    assert_pin(args[0], false);
-    const mcu_pin_obj_t *pin = MP_OBJ_TO_PTR(args[0]);
+    const mcu_pin_obj_t *pin = validate_is_free_pin(args[0]);
 
     analogio_analogout_obj_t *self = m_new_obj(analogio_analogout_obj_t);
     self->base.type = &analogio_analogout_type;
-    assert_pin_free(pin);
     common_hal_analogio_analogout_construct(self, pin);
 
-    return self;
+    return MP_OBJ_FROM_PTR(self);
 }
 
 //|   .. method:: deinit()
diff --git a/shared-bindings/audiobusio/I2SOut.c b/shared-bindings/audiobusio/I2SOut.c
index 8f7382fde5..45f7037954 100644
--- a/shared-bindings/audiobusio/I2SOut.c
+++ b/shared-bindings/audiobusio/I2SOut.c
@@ -105,17 +105,9 @@ STATIC mp_obj_t audiobusio_i2sout_make_new(const mp_obj_type_t *type, size_t n_a
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    mp_obj_t bit_clock_obj = args[ARG_bit_clock].u_obj;
-    assert_pin(bit_clock_obj, false);
-    const mcu_pin_obj_t *bit_clock = MP_OBJ_TO_PTR(bit_clock_obj);
-
-    mp_obj_t word_select_obj = args[ARG_word_select].u_obj;
-    assert_pin(word_select_obj, false);
-    const mcu_pin_obj_t *word_select = MP_OBJ_TO_PTR(word_select_obj);
-
-    mp_obj_t data_obj = args[ARG_data].u_obj;
-    assert_pin(data_obj, false);
-    const mcu_pin_obj_t *data = MP_OBJ_TO_PTR(data_obj);
+    const mcu_pin_obj_t *bit_clock = validate_is_free_pin(args[ARG_bit_clock].u_obj);
+    const mcu_pin_obj_t *word_select = validate_is_free_pin(args[ARG_word_select].u_obj);
+    const mcu_pin_obj_t *data = validate_is_free_pin(args[ARG_data].u_obj);
 
     audiobusio_i2sout_obj_t *self = m_new_obj_with_finaliser(audiobusio_i2sout_obj_t);
     self->base.type = &audiobusio_i2sout_type;
diff --git a/shared-bindings/audiobusio/PDMIn.c b/shared-bindings/audiobusio/PDMIn.c
index 0c92c24780..65bc5a9d26 100644
--- a/shared-bindings/audiobusio/PDMIn.c
+++ b/shared-bindings/audiobusio/PDMIn.c
@@ -104,15 +104,8 @@ STATIC mp_obj_t audiobusio_pdmin_make_new(const mp_obj_type_t *type, size_t n_ar
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    mp_obj_t clock_pin_obj = args[ARG_clock_pin].u_obj;
-    assert_pin(clock_pin_obj, false);
-    const mcu_pin_obj_t *clock_pin = MP_OBJ_TO_PTR(clock_pin_obj);
-    assert_pin_free(clock_pin);
-
-    mp_obj_t data_pin_obj = args[ARG_data_pin].u_obj;
-    assert_pin(data_pin_obj, false);
-    const mcu_pin_obj_t *data_pin = MP_OBJ_TO_PTR(data_pin_obj);
-    assert_pin_free(data_pin);
+    const mcu_pin_obj_t *clock_pin = validate_is_free_pin(args[ARG_clock_pin].u_obj);
+    const mcu_pin_obj_t *data_pin = validate_is_free_pin(args[ARG_data_pin].u_obj);
 
     // create PDMIn object from the given pin
     audiobusio_pdmin_obj_t *self = m_new_obj(audiobusio_pdmin_obj_t);
diff --git a/shared-bindings/audioio/AudioOut.c b/shared-bindings/audioio/AudioOut.c
index eb4ef1fc6c..687db22d3f 100644
--- a/shared-bindings/audioio/AudioOut.c
+++ b/shared-bindings/audioio/AudioOut.c
@@ -104,16 +104,8 @@ STATIC mp_obj_t audioio_audioout_make_new(const mp_obj_type_t *type, size_t n_ar
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    mp_obj_t left_channel_obj = args[ARG_left_channel].u_obj;
-    assert_pin(left_channel_obj, false);
-    const mcu_pin_obj_t *left_channel_pin = MP_OBJ_TO_PTR(left_channel_obj);
-
-    mp_obj_t right_channel_obj = args[ARG_right_channel].u_obj;
-    const mcu_pin_obj_t *right_channel_pin = NULL;
-    if (right_channel_obj != mp_const_none) {
-        assert_pin(right_channel_obj, false);
-        right_channel_pin = MP_OBJ_TO_PTR(right_channel_obj);
-    }
+    const mcu_pin_obj_t *left_channel_pin = validate_is_free_pin(args[ARG_left_channel].u_obj);
+    const mcu_pin_obj_t *right_channel_pin = validate_is_free_pin_or_none(args[ARG_right_channel].u_obj);
 
     // create AudioOut object from the given pin
     audioio_audioout_obj_t *self = m_new_obj(audioio_audioout_obj_t);
diff --git a/shared-bindings/audiopwmio/PWMAudioOut.c b/shared-bindings/audiopwmio/PWMAudioOut.c
index 60bf085002..c1c11f9cdc 100644
--- a/shared-bindings/audiopwmio/PWMAudioOut.c
+++ b/shared-bindings/audiopwmio/PWMAudioOut.c
@@ -107,16 +107,8 @@ STATIC mp_obj_t audiopwmio_pwmaudioout_make_new(const mp_obj_type_t *type, size_
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    mp_obj_t left_channel_obj = args[ARG_left_channel].u_obj;
-    assert_pin(left_channel_obj, false);
-    const mcu_pin_obj_t *left_channel_pin = MP_OBJ_TO_PTR(left_channel_obj);
-
-    mp_obj_t right_channel_obj = args[ARG_right_channel].u_obj;
-    const mcu_pin_obj_t *right_channel_pin = NULL;
-    if (right_channel_obj != mp_const_none) {
-        assert_pin(right_channel_obj, false);
-        right_channel_pin = MP_OBJ_TO_PTR(right_channel_obj);
-    }
+    const mcu_pin_obj_t *left_channel_pin = validate_is_free_pin(args[ARG_left_channel].u_obj);
+    const mcu_pin_obj_t *right_channel_pin = validate_is_free_pin_or_none(args[ARG_right_channel].u_obj)
 
     // create AudioOut object from the given pin
     audiopwmio_pwmaudioout_obj_t *self = m_new_obj(audiopwmio_pwmaudioout_obj_t);
diff --git a/shared-bindings/bitbangio/I2C.c b/shared-bindings/bitbangio/I2C.c
index 01a128393b..bdfbfb2ca9 100644
--- a/shared-bindings/bitbangio/I2C.c
+++ b/shared-bindings/bitbangio/I2C.c
@@ -63,10 +63,9 @@ STATIC mp_obj_t bitbangio_i2c_make_new(const mp_obj_type_t *type, size_t n_args,
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-    assert_pin(args[ARG_scl].u_obj, false);
-    assert_pin(args[ARG_sda].u_obj, false);
-    const mcu_pin_obj_t* scl = MP_OBJ_TO_PTR(args[ARG_scl].u_obj);
-    const mcu_pin_obj_t* sda = MP_OBJ_TO_PTR(args[ARG_sda].u_obj);
+
+    const mcu_pin_obj_t* scl = validate_is_free_pin(args[ARG_scl].u_obj);
+    const mcu_pin_obj_t* sda = validate_is_free_pin(args[ARG_sda].u_obj);
 
     bitbangio_i2c_obj_t *self = m_new_obj(bitbangio_i2c_obj_t);
     self->base.type = &bitbangio_i2c_type;
diff --git a/shared-bindings/bitbangio/OneWire.c b/shared-bindings/bitbangio/OneWire.c
index 73bedcd8d5..20ca81c5dc 100644
--- a/shared-bindings/bitbangio/OneWire.c
+++ b/shared-bindings/bitbangio/OneWire.c
@@ -69,9 +69,8 @@ STATIC mp_obj_t bitbangio_onewire_make_new(const mp_obj_type_t *type, size_t n_a
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-    assert_pin(args[ARG_pin].u_obj, false);
-    const mcu_pin_obj_t* pin = MP_OBJ_TO_PTR(args[ARG_pin].u_obj);
-    assert_pin_free(pin);
+
+    const mcu_pin_obj_t* pin = validate_is_free_pin(args[ARG_pin].u_obj);
 
     bitbangio_onewire_obj_t *self = m_new_obj(bitbangio_onewire_obj_t);
     self->base.type = &bitbangio_onewire_type;
diff --git a/shared-bindings/bitbangio/SPI.c b/shared-bindings/bitbangio/SPI.c
index 9a51bde665..4623523523 100644
--- a/shared-bindings/bitbangio/SPI.c
+++ b/shared-bindings/bitbangio/SPI.c
@@ -71,12 +71,10 @@ STATIC mp_obj_t bitbangio_spi_make_new(const mp_obj_type_t *type, size_t n_args,
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-    assert_pin(args[ARG_clock].u_obj, false);
-    assert_pin(args[ARG_MOSI].u_obj, true);
-    assert_pin(args[ARG_MISO].u_obj, true);
-    const mcu_pin_obj_t* clock = MP_OBJ_TO_PTR(args[ARG_clock].u_obj);
-    const mcu_pin_obj_t* mosi = MP_OBJ_TO_PTR(args[ARG_MOSI].u_obj);
-    const mcu_pin_obj_t* miso = MP_OBJ_TO_PTR(args[ARG_MISO].u_obj);
+
+    const mcu_pin_obj_t* clock = validate_is_free_pin(args[ARG_clock].u_obj);
+    const mcu_pin_obj_t* mosi = validate_is_free_pin_or_none(args[ARG_MOSI].u_obj);
+    const mcu_pin_obj_t* miso = validate_is_free_pin_or_none(args[ARG_MISO].u_obj);
 
     bitbangio_spi_obj_t *self = m_new_obj(bitbangio_spi_obj_t);
     self->base.type = &bitbangio_spi_type;
diff --git a/shared-bindings/busio/I2C.c b/shared-bindings/busio/I2C.c
index 50a95beb2e..618a5ad320 100644
--- a/shared-bindings/busio/I2C.c
+++ b/shared-bindings/busio/I2C.c
@@ -76,12 +76,10 @@ STATIC mp_obj_t busio_i2c_make_new(const mp_obj_type_t *type, size_t n_args, con
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-    assert_pin(args[ARG_scl].u_obj, false);
-    assert_pin(args[ARG_sda].u_obj, false);
-    const mcu_pin_obj_t* scl = MP_OBJ_TO_PTR(args[ARG_scl].u_obj);
-    assert_pin_free(scl);
-    const mcu_pin_obj_t* sda = MP_OBJ_TO_PTR(args[ARG_sda].u_obj);
-    assert_pin_free(sda);
+
+    const mcu_pin_obj_t* scl = validate_is_free_pin(args[ARG_scl].u_obj);
+    const mcu_pin_obj_t* sda = validate_is_free_pin(args[ARG_sda].u_obj);
+
     common_hal_busio_i2c_construct(self, scl, sda, args[ARG_frequency].u_int, args[ARG_timeout].u_int);
     return (mp_obj_t)self;
 }
diff --git a/shared-bindings/busio/OneWire.c b/shared-bindings/busio/OneWire.c
index aca2a3ef20..b28495096d 100644
--- a/shared-bindings/busio/OneWire.c
+++ b/shared-bindings/busio/OneWire.c
@@ -69,9 +69,7 @@ STATIC mp_obj_t busio_onewire_make_new(const mp_obj_type_t *type, size_t n_args,
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-    assert_pin(args[ARG_pin].u_obj, false);
-    const mcu_pin_obj_t* pin = MP_OBJ_TO_PTR(args[ARG_pin].u_obj);
-    assert_pin_free(pin);
+    const mcu_pin_obj_t* pin = validate_is_free_pin(args[ARG_pin].u_obj);
 
     busio_onewire_obj_t *self = m_new_obj(busio_onewire_obj_t);
     self->base.type = &busio_onewire_type;
diff --git a/shared-bindings/busio/SPI.c b/shared-bindings/busio/SPI.c
index 828ffb8d00..ca84c0f246 100644
--- a/shared-bindings/busio/SPI.c
+++ b/shared-bindings/busio/SPI.c
@@ -89,17 +89,13 @@ STATIC mp_obj_t busio_spi_make_new(const mp_obj_type_t *type, size_t n_args, con
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-    assert_pin(args[ARG_clock].u_obj, false);
-    assert_pin(args[ARG_MOSI].u_obj, true);
-    assert_pin(args[ARG_MISO].u_obj, true);
-    const mcu_pin_obj_t* clock = MP_OBJ_TO_PTR(args[ARG_clock].u_obj);
-    assert_pin_free(clock);
-    const mcu_pin_obj_t* mosi = MP_OBJ_TO_PTR(args[ARG_MOSI].u_obj);
-    assert_pin_free(mosi);
-    const mcu_pin_obj_t* miso = MP_OBJ_TO_PTR(args[ARG_MISO].u_obj);
-    assert_pin_free(miso);
+
+    const mcu_pin_obj_t* clock = validate_is_free_pin(args[ARG_clock].u_obj);
+    const mcu_pin_obj_t* mosi = validate_is_free_pin_or_none(args[ARG_MOSI].u_obj);
+    const mcu_pin_obj_t* miso = validate_is_free_pin_or_none(args[ARG_MISO].u_obj);
+
     common_hal_busio_spi_construct(self, clock, mosi, miso);
-    return (mp_obj_t)self;
+    return MP_OBJ_FROM_PTR(self);
 }
 
 //|   .. method:: deinit()
diff --git a/shared-bindings/busio/UART.c b/shared-bindings/busio/UART.c
index 02c5afb16e..ffa50fd7d8 100644
--- a/shared-bindings/busio/UART.c
+++ b/shared-bindings/busio/UART.c
@@ -105,13 +105,12 @@ STATIC mp_obj_t busio_uart_make_new(const mp_obj_type_t *type, size_t n_args, co
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    assert_pin(args[ARG_rx].u_obj, true);
-    const mcu_pin_obj_t* rx = MP_OBJ_TO_PTR(args[ARG_rx].u_obj);
-    assert_pin_free(rx);
+    const mcu_pin_obj_t* rx = validate_is_free_pin_or_none(args[ARG_rx].u_obj);
+    const mcu_pin_obj_t* tx = validate_is_free_pin_or_none(args[ARG_tx].u_obj);
 
-    assert_pin(args[ARG_tx].u_obj, true);
-    const mcu_pin_obj_t* tx = MP_OBJ_TO_PTR(args[ARG_tx].u_obj);
-    assert_pin_free(tx);
+    if ( (tx == NULL) && (rx == NULL) ) {
+        mp_raise_ValueError(translate("tx and rx cannot both be None"));
+    }
 
     uint8_t bits = args[ARG_bits].u_int;
     if (bits < 7 || bits > 9) {
@@ -133,12 +132,11 @@ STATIC mp_obj_t busio_uart_make_new(const mp_obj_type_t *type, size_t n_args, co
     mp_float_t timeout = mp_obj_get_float(args[ARG_timeout].u_obj);
     validate_timeout(timeout);
 
-    const mcu_pin_obj_t* rts = MP_OBJ_TO_PTR(args[ARG_rts].u_obj);
+    const mcu_pin_obj_t* rts = validate_is_free_pin_or_none(args[ARG_rts].u_obj);
+    const mcu_pin_obj_t* cts = validate_is_free_pin_or_none(args[ARG_cts].u_obj);
+    const mcu_pin_obj_t* rs485_dir = validate_is_free_pin_or_none(args[ARG_rs485_dir].u_obj);
 
-    const mcu_pin_obj_t* cts = MP_OBJ_TO_PTR(args[ARG_cts].u_obj);
-
-    const mcu_pin_obj_t* rs485_dir = args[ARG_rs485_dir].u_obj;
-    bool rs485_invert = args[ARG_rs485_invert].u_bool;
+    const bool rs485_invert = args[ARG_rs485_invert].u_bool;
 
     common_hal_busio_uart_construct(self, tx, rx, rts, cts, rs485_dir, rs485_invert,
                                     args[ARG_baudrate].u_int, bits, parity, stop, timeout,
diff --git a/shared-bindings/digitalio/DigitalInOut.c b/shared-bindings/digitalio/DigitalInOut.c
index 16472c12c1..1610c83f8b 100644
--- a/shared-bindings/digitalio/DigitalInOut.c
+++ b/shared-bindings/digitalio/DigitalInOut.c
@@ -68,12 +68,10 @@ STATIC mp_obj_t digitalio_digitalinout_make_new(const mp_obj_type_t *type,
     digitalio_digitalinout_obj_t *self = m_new_obj(digitalio_digitalinout_obj_t);
     self->base.type = &digitalio_digitalinout_type;
 
-    assert_pin(args[0], false);
-    mcu_pin_obj_t *pin = MP_OBJ_TO_PTR(args[0]);
-    assert_pin_free(pin);
+    mcu_pin_obj_t *pin = validate_is_free_pin(args[0]);
     common_hal_digitalio_digitalinout_construct(self, pin);
 
-    return (mp_obj_t)self;
+    return MP_OBJ_FROM_PTR(self);
 }
 
 //|   .. method:: deinit()
diff --git a/shared-bindings/displayio/Display.c b/shared-bindings/displayio/Display.c
index 5759e8ad22..9fa976b86b 100644
--- a/shared-bindings/displayio/Display.c
+++ b/shared-bindings/displayio/Display.c
@@ -141,13 +141,7 @@ STATIC mp_obj_t displayio_display_make_new(const mp_obj_type_t *type, size_t n_a
     mp_buffer_info_t bufinfo;
     mp_get_buffer_raise(args[ARG_init_sequence].u_obj, &bufinfo, MP_BUFFER_READ);
 
-    mp_obj_t backlight_pin_obj = args[ARG_backlight_pin].u_obj;
-    assert_pin(backlight_pin_obj, true);
-    const mcu_pin_obj_t* backlight_pin = NULL;
-    if (backlight_pin_obj != NULL && backlight_pin_obj != mp_const_none) {
-        backlight_pin = MP_OBJ_TO_PTR(backlight_pin_obj);
-        assert_pin_free(backlight_pin);
-    }
+    const mcu_pin_obj_t* backlight_pin = validate_is_free_pin_or_none(args[ARG_backlight_pin].u_obj);
 
     mp_float_t brightness = mp_obj_get_float(args[ARG_brightness].u_obj);
 
diff --git a/shared-bindings/displayio/EPaperDisplay.c b/shared-bindings/displayio/EPaperDisplay.c
index 81e06f82f9..60a3838a40 100644
--- a/shared-bindings/displayio/EPaperDisplay.c
+++ b/shared-bindings/displayio/EPaperDisplay.c
@@ -129,13 +129,7 @@ STATIC mp_obj_t displayio_epaperdisplay_make_new(const mp_obj_type_t *type, size
     mp_get_buffer_raise(args[ARG_stop_sequence].u_obj, &stop_bufinfo, MP_BUFFER_READ);
 
 
-    mp_obj_t busy_pin_obj = args[ARG_busy_pin].u_obj;
-    assert_pin(busy_pin_obj, true);
-    const mcu_pin_obj_t* busy_pin = NULL;
-    if (busy_pin_obj != NULL && busy_pin_obj != mp_const_none) {
-        busy_pin = MP_OBJ_TO_PTR(busy_pin_obj);
-        assert_pin_free(busy_pin);
-    }
+    const mcu_pin_obj_t* busy_pin = validate_is_free_pin_or_none(args[ARG_busy_pin].u_obj);
 
     mp_int_t rotation = args[ARG_rotation].u_int;
     if (rotation % 90 != 0) {
diff --git a/shared-bindings/frequencyio/FrequencyIn.c b/shared-bindings/frequencyio/FrequencyIn.c
index e2b924c079..349ef7e970 100644
--- a/shared-bindings/frequencyio/FrequencyIn.c
+++ b/shared-bindings/frequencyio/FrequencyIn.c
@@ -87,9 +87,7 @@ STATIC mp_obj_t frequencyio_frequencyin_make_new(const mp_obj_type_t *type, size
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    assert_pin(args[ARG_pin].u_obj, false);
-    mcu_pin_obj_t* pin = MP_OBJ_TO_PTR(args[ARG_pin].u_obj);
-    assert_pin_free(pin);
+    mcu_pin_obj_t* pin = validate_is_free_pin(args[ARG_pin].u_obj);
 
     const uint16_t capture_period = args[ARG_capture_period].u_int;
 
diff --git a/shared-bindings/i2cslave/I2CSlave.c b/shared-bindings/i2cslave/I2CSlave.c
index c98ea52e06..b7980d5174 100644
--- a/shared-bindings/i2cslave/I2CSlave.c
+++ b/shared-bindings/i2cslave/I2CSlave.c
@@ -77,12 +77,8 @@ STATIC mp_obj_t i2cslave_i2c_slave_make_new(const mp_obj_type_t *type, size_t n_
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    assert_pin(args[ARG_scl].u_obj, false);
-    assert_pin(args[ARG_sda].u_obj, false);
-    const mcu_pin_obj_t* scl = MP_OBJ_TO_PTR(args[ARG_scl].u_obj);
-    assert_pin_free(scl);
-    const mcu_pin_obj_t* sda = MP_OBJ_TO_PTR(args[ARG_sda].u_obj);
-    assert_pin_free(sda);
+    const mcu_pin_obj_t* scl = validate_is_free_pin(args[ARG_scl].u_obj);
+    const mcu_pin_obj_t* sda = validate_is_free_pin(args[ARG_sda].u_obj);
 
     mp_obj_iter_buf_t iter_buf;
     mp_obj_t iterable = mp_getiter(args[ARG_addresses].u_obj, &iter_buf);
diff --git a/shared-bindings/microcontroller/Pin.c b/shared-bindings/microcontroller/Pin.c
index 3635f0afbd..ef80088272 100644
--- a/shared-bindings/microcontroller/Pin.c
+++ b/shared-bindings/microcontroller/Pin.c
@@ -84,10 +84,35 @@ const mp_obj_type_t mcu_pin_type = {
     .print = mcu_pin_print
 };
 
-void assert_pin(mp_obj_t obj, bool none_ok) {
-    if ((obj != mp_const_none || !none_ok) && !MP_OBJ_IS_TYPE(obj, &mcu_pin_type)) {
+mcu_pin_obj_t *validate_is_pin(mp_obj_t obj) {
+    if (!MP_OBJ_IS_TYPE(obj, &mcu_pin_type)) {
         mp_raise_TypeError_varg(translate("Expected a %q"), mcu_pin_type.name);
     }
+    return MP_OBJ_TO_PTR(obj);
+}
+
+// Validate that the obj is a pin or None. Return an mcu_pin_obj_t* or NULL, correspondingly.
+mcu_pin_obj_t *validate_is_pin_or_none(mp_obj_t obj) {
+    if (obj == mp_const_none) {
+        return NULL;
+    }
+    return validate_is_pin(obj);
+}
+
+mcu_pin_obj_t *validate_is_free_pin(mp_obj_t obj) {
+    mcu_pin_obj_t *pin = validate_is_pin(obj);
+    assert_pin_free(pin);
+    return pin;
+}
+
+// Validate that the obj is a free pin or None. Return an mcu_pin_obj_t* or NULL, correspondingly.
+mcu_pin_obj_t *validate_is_free_pin_or_none(mp_obj_t obj) {
+    if (obj == mp_const_none) {
+        return NULL;
+    }
+    mcu_pin_obj_t *pin = validate_is_pin(obj);
+    assert_pin_free(pin);
+    return pin;
 }
 
 void assert_pin_free(const mcu_pin_obj_t* pin) {
diff --git a/shared-bindings/microcontroller/Pin.h b/shared-bindings/microcontroller/Pin.h
index 2d15dd5c58..2b40838278 100644
--- a/shared-bindings/microcontroller/Pin.h
+++ b/shared-bindings/microcontroller/Pin.h
@@ -33,7 +33,11 @@
 // Type object used in Python. Should be shared between ports.
 extern const mp_obj_type_t mcu_pin_type;
 
-void assert_pin(mp_obj_t obj, bool none_ok);
+mcu_pin_obj_t *validate_is_pin(mp_obj_t obj);
+mcu_pin_obj_t *validate_is_pin_or_none(mp_obj_t obj);
+mcu_pin_obj_t *validate_is_free_pin(mp_obj_t obj);
+mcu_pin_obj_t *validate_is_free_pin_or_none(mp_obj_t obj);
+
 void assert_pin_free(const mcu_pin_obj_t* pin);
 
 bool common_hal_mcu_pin_is_free(const mcu_pin_obj_t* pin);
diff --git a/shared-bindings/ps2io/Ps2.c b/shared-bindings/ps2io/Ps2.c
index fb5c24b85c..f5aa70907a 100644
--- a/shared-bindings/ps2io/Ps2.c
+++ b/shared-bindings/ps2io/Ps2.c
@@ -77,12 +77,9 @@ STATIC mp_obj_t ps2io_ps2_make_new(const mp_obj_type_t *type, size_t n_args, con
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-    assert_pin(args[ARG_clkpin].u_obj, false);
-    assert_pin(args[ARG_datapin].u_obj, false);
-    const mcu_pin_obj_t* clkpin = MP_OBJ_TO_PTR(args[ARG_clkpin].u_obj);
-    assert_pin_free(clkpin);
-    const mcu_pin_obj_t* datapin = MP_OBJ_TO_PTR(args[ARG_datapin].u_obj);
-    assert_pin_free(datapin);
+
+    const mcu_pin_obj_t* clkpin = validate_is_free_pin(args[ARG_clkpin].u_obj);
+    const mcu_pin_obj_t* datapin = validate_is_free_pin(args[ARG_datapin].u_obj);
 
     ps2io_ps2_obj_t *self = m_new_obj(ps2io_ps2_obj_t);
     self->base.type = &ps2io_ps2_type;
diff --git a/shared-bindings/pulseio/PWMOut.c b/shared-bindings/pulseio/PWMOut.c
index 53b88c61a5..d04b469c1c 100644
--- a/shared-bindings/pulseio/PWMOut.c
+++ b/shared-bindings/pulseio/PWMOut.c
@@ -96,10 +96,7 @@ STATIC mp_obj_t pulseio_pwmout_make_new(const mp_obj_type_t *type, size_t n_args
     mp_arg_val_t parsed_args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, parsed_args);
 
-    mp_obj_t pin_obj = parsed_args[ARG_pin].u_obj;
-    assert_pin(pin_obj, false);
-    const mcu_pin_obj_t *pin = MP_OBJ_TO_PTR(pin_obj);
-    assert_pin_free(pin);
+    const mcu_pin_obj_t *pin = validate_is_free_pin(parsed_args[ARG_pin].u_obj);
 
     uint16_t duty_cycle = parsed_args[ARG_duty_cycle].u_int;
     uint32_t frequency = parsed_args[ARG_frequency].u_int;
diff --git a/shared-bindings/pulseio/PulseIn.c b/shared-bindings/pulseio/PulseIn.c
index 8b69109f04..dbab253af4 100644
--- a/shared-bindings/pulseio/PulseIn.c
+++ b/shared-bindings/pulseio/PulseIn.c
@@ -90,9 +90,7 @@ STATIC mp_obj_t pulseio_pulsein_make_new(const mp_obj_type_t *type, size_t n_arg
     };
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
-    assert_pin(args[ARG_pin].u_obj, false);
-    const mcu_pin_obj_t* pin = MP_OBJ_TO_PTR(args[ARG_pin].u_obj);
-    assert_pin_free(pin);
+    const mcu_pin_obj_t* pin = validate_is_free_pin(args[ARG_pin].u_obj);
 
     pulseio_pulsein_obj_t *self = m_new_obj(pulseio_pulsein_obj_t);
     self->base.type = &pulseio_pulsein_type;
diff --git a/shared-bindings/rotaryio/IncrementalEncoder.c b/shared-bindings/rotaryio/IncrementalEncoder.c
index f2f1578478..78dccacb52 100644
--- a/shared-bindings/rotaryio/IncrementalEncoder.c
+++ b/shared-bindings/rotaryio/IncrementalEncoder.c
@@ -73,13 +73,8 @@ STATIC mp_obj_t rotaryio_incrementalencoder_make_new(const mp_obj_type_t *type,
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
 
-    assert_pin(args[ARG_pin_a].u_obj, false);
-    const mcu_pin_obj_t* pin_a = MP_OBJ_TO_PTR(args[ARG_pin_a].u_obj);
-    assert_pin_free(pin_a);
-
-    assert_pin(args[ARG_pin_b].u_obj, false);
-    const mcu_pin_obj_t* pin_b = MP_OBJ_TO_PTR(args[ARG_pin_b].u_obj);
-    assert_pin_free(pin_b);
+    const mcu_pin_obj_t* pin_a = validate_is_free_pin(args[ARG_pin_a].u_obj);
+    const mcu_pin_obj_t* pin_b = validate_is_free_pin(args[ARG_pin_b].u_obj);
 
     rotaryio_incrementalencoder_obj_t *self = m_new_obj(rotaryio_incrementalencoder_obj_t);
     self->base.type = &rotaryio_incrementalencoder_type;
diff --git a/shared-bindings/touchio/TouchIn.c b/shared-bindings/touchio/TouchIn.c
index 33d369c748..5eadb2cc49 100644
--- a/shared-bindings/touchio/TouchIn.c
+++ b/shared-bindings/touchio/TouchIn.c
@@ -66,10 +66,7 @@ STATIC mp_obj_t touchio_touchin_make_new(const mp_obj_type_t *type,
     mp_arg_check_num(n_args, kw_args, 1, 1, false);
 
     // 1st argument is the pin
-    mp_obj_t pin_obj = args[0];
-    assert_pin(pin_obj, false);
-    const mcu_pin_obj_t *pin = MP_OBJ_TO_PTR(pin_obj);
-    assert_pin_free(pin);
+    const mcu_pin_obj_t *pin = validate_is_free_pin(args[0]);
 
     touchio_touchin_obj_t *self = m_new_obj(touchio_touchin_obj_t);
     self->base.type = &touchio_touchin_type;
diff --git a/shared-bindings/wiznet/wiznet5k.c b/shared-bindings/wiznet/wiznet5k.c
index ac89cc691e..1b7f76e122 100644
--- a/shared-bindings/wiznet/wiznet5k.c
+++ b/shared-bindings/wiznet/wiznet5k.c
@@ -78,10 +78,10 @@ STATIC mp_obj_t wiznet5k_make_new(const mp_obj_type_t *type, size_t n_args, cons
     mp_arg_val_t args[MP_ARRAY_SIZE(allowed_args)];
     mp_arg_parse_all(n_args, pos_args, kw_args, MP_ARRAY_SIZE(allowed_args), allowed_args, args);
     // TODO check type of ARG_spi?
-    assert_pin(args[ARG_cs].u_obj, false);
-    assert_pin(args[ARG_rst].u_obj, true); // may be NULL
+    const mcu_pin_obj_t *cs = validate_is_free_pin(args[ARG_cs].u_obj);
+    const mcu_pin_obj_t *rst = validate_is_free_pin_or_none(args[ARG_rst].u_obj);
 
-    mp_obj_t ret = wiznet5k_create(args[ARG_spi].u_obj, args[ARG_cs].u_obj, args[ARG_rst].u_obj);
+    mp_obj_t ret = wiznet5k_create(args[ARG_spi].u_obj, cs, rst);
     if (args[ARG_dhcp].u_bool) wiznet5k_start_dhcp();
     return ret;
 }
diff --git a/shared-module/bitbangio/SPI.c b/shared-module/bitbangio/SPI.c
index d02adf34fb..e0ff1184fe 100644
--- a/shared-module/bitbangio/SPI.c
+++ b/shared-module/bitbangio/SPI.c
@@ -45,7 +45,7 @@ void shared_module_bitbangio_spi_construct(bitbangio_spi_obj_t *self,
     }
     common_hal_digitalio_digitalinout_switch_to_output(&self->clock, self->polarity == 1, DRIVE_MODE_PUSH_PULL);
 
-    if (mosi != mp_const_none) {
+    if (mosi != NULL) {
         result = common_hal_digitalio_digitalinout_construct(&self->mosi, mosi);
         if (result != DIGITALINOUT_OK) {
             common_hal_digitalio_digitalinout_deinit(&self->clock);
@@ -55,12 +55,12 @@ void shared_module_bitbangio_spi_construct(bitbangio_spi_obj_t *self,
         common_hal_digitalio_digitalinout_switch_to_output(&self->mosi, false, DRIVE_MODE_PUSH_PULL);
     }
 
-    if (miso != mp_const_none) {
+    if (miso != NULL) {
         // Starts out as input by default, no need to change.
         result = common_hal_digitalio_digitalinout_construct(&self->miso, miso);
         if (result != DIGITALINOUT_OK) {
             common_hal_digitalio_digitalinout_deinit(&self->clock);
-            if (mosi != mp_const_none) {
+            if (mosi != NULL) {
                 common_hal_digitalio_digitalinout_deinit(&self->mosi);
             }
             mp_raise_ValueError(translate("MISO pin init failed."));
diff --git a/shared-module/board/__init__.c b/shared-module/board/__init__.c
index bbf177384b..789318a053 100644
--- a/shared-module/board/__init__.c
+++ b/shared-module/board/__init__.c
@@ -103,12 +103,12 @@ mp_obj_t common_hal_board_create_uart(void) {
 #ifdef DEFAULT_UART_BUS_RTS
     const mcu_pin_obj_t* rts = MP_OBJ_TO_PTR(DEFAULT_UART_BUS_RTS);
 #else
-    const mcu_pin_obj_t* rts = mp_const_none;
+    const mcu_pin_obj_t* rts = NULL;
 #endif
 #ifdef DEFAULT_UART_BUS_CTS
     const mcu_pin_obj_t* cts = MP_OBJ_TO_PTR(DEFAULT_UART_BUS_CTS);
 #else
-    const mcu_pin_obj_t* cts = mp_const_none;
+    const mcu_pin_obj_t* cts = NULL;
 #endif
 #ifdef DEFAULT_UART_IS_RS485
     const mcu_pin_obj_t* rs485_dir = MP_OBJ_TO_PTR(DEFAULT_UART_BUS_RS485DIR);
@@ -118,7 +118,7 @@ mp_obj_t common_hal_board_create_uart(void) {
     const bool rs485_invert = false;
 #endif
 #else
-    const mcu_pin_obj_t* rs485_dir = mp_const_none;
+    const mcu_pin_obj_t* rs485_dir = NULL;
     const bool rs485_invert = false;
 #endif