new pin validation routines; don't use mp_const_none if NULL will do

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;

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;

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;

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;

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;

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;

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;

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;

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() {

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,

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->clock_pin = NULL;
-    self->data_pin = mp_const_none;
+    self->data_pin = NULL;
 }
 
 uint8_t common_hal_audiobusio_pdmin_get_bit_depth(audiobusio_pdmin_obj_t* self) {

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
 }
 

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 mosi_none = mosi == NULL;
-    bool miso_none = miso == mp_const_none || miso == NULL;
+    bool miso_none = miso == NULL;
     uint32_t mosi_pinmux = 0;
     uint32_t miso_pinmux = 0;
     uint8_t clock_pad = 0;

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_tx = tx != NULL;
-    bool have_rx = rx != mp_const_none;
+    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;
             }

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(

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) {

ports/cxd56/common-hal/analogio/AnalogIn.c

@@ -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) {

ports/cxd56/common-hal/busio/UART.c

@@ -60,7 +60,7 @@ 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"));
     }
 

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) {

ports/cxd56/common-hal/pulseio/PWMOut.c

@@ -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) {

ports/cxd56/common-hal/pulseio/PulseIn.c

@@ -116,11 +116,11 @@ 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) {
@@ -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;
 }
- 

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) {

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_tx = tx != NULL;
-    bool have_rx = rx != mp_const_none;
+    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 (rs485_dir != NULL) {
-      if ((rts != mp_const_none) || (cts != mp_const_none)) {
+      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) {
@@ -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;

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(

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;

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;

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) {

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);

ports/nrf/common-hal/busio/UART.c

@@ -135,7 +135,7 @@ 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"));
     }
 
@@ -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,
+        .pseltxd = (tx == NULL) ? NRF_UARTE_PSEL_DISCONNECTED : tx->number,
-        .pselrxd = (rx == mp_const_none) ? NRF_UARTE_PSEL_DISCONNECTED : rx->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 {

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(

ports/stm32f4/common-hal/analogio/AnalogIn.c

@@ -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) {

ports/stm32f4/common-hal/analogio/AnalogOut.c

@@ -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

ports/stm32f4/common-hal/busio/I2C.c

@@ -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->sda = NULL;
-    self->scl = mp_const_none;
+    self->scl = NULL;
 }
 
 bool common_hal_busio_i2c_probe(busio_i2c_obj_t *self, uint8_t addr) {

ports/stm32f4/common-hal/busio/SPI.c

@@ -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) {
@@ -137,7 +137,7 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
                     }
                 }
             // 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)) {
@@ -154,7 +154,7 @@ void common_hal_busio_spi_construct(busio_spi_obj_t *self,
                     }
                 }
             // 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)) {
@@ -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->mosi != NULL && miso == NULL) ||
-        (self->sck != NULL && self->miso != NULL && mosi == mp_const_none)) {
+        (self->sck != NULL && self->miso != NULL && mosi == NULL)) {
         SPIx = mcu_spi_banks[self->sck->spi_index - 1];
     } else {
         if (spi_taken) {
@@ -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) {
@@ -287,9 +287,9 @@ 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->sck = NULL;
-    self->mosi = mp_const_none;
+    self->mosi = NULL;
-    self->miso = mp_const_none;
+    self->miso = NULL;
 }
 
 bool common_hal_busio_spi_configure(busio_spi_obj_t *self,

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->tx = NULL;
-    self->rx = mp_const_none;
+    self->rx = NULL;
     gc_free(self->rbuf.buf);
     self->rbuf.size = 0;
     self->rbuf.iput = self->rbuf.iget = 0;

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(

ports/stm32f4/common-hal/pulseio/PWMOut.c

@@ -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]) {

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];
+    const mcu_pin_obj_t *pin = validate_is_free_pin(args[0]);
-    assert_pin(pin_obj, false);
 
     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()

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 = validate_is_free_pin(args[0]);
-    const mcu_pin_obj_t *pin = MP_OBJ_TO_PTR(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()

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;
+    const mcu_pin_obj_t *bit_clock = validate_is_free_pin(args[ARG_bit_clock].u_obj);
-    assert_pin(bit_clock_obj, false);
+    const mcu_pin_obj_t *word_select = validate_is_free_pin(args[ARG_word_select].u_obj);
-    const mcu_pin_obj_t *bit_clock = MP_OBJ_TO_PTR(bit_clock_obj);
+    const mcu_pin_obj_t *data = validate_is_free_pin(args[ARG_data].u_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);
 
     audiobusio_i2sout_obj_t *self = m_new_obj_with_finaliser(audiobusio_i2sout_obj_t);
     self->base.type = &audiobusio_i2sout_type;

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;
+    const mcu_pin_obj_t *clock_pin = validate_is_free_pin(args[ARG_clock_pin].u_obj);
-    assert_pin(clock_pin_obj, false);
+    const mcu_pin_obj_t *data_pin = validate_is_free_pin(args[ARG_data_pin].u_obj);
-    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);
 
     // create PDMIn object from the given pin
     audiobusio_pdmin_obj_t *self = m_new_obj(audiobusio_pdmin_obj_t);

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;
+    const mcu_pin_obj_t *left_channel_pin = validate_is_free_pin(args[ARG_left_channel].u_obj);
-    assert_pin(left_channel_obj, false);
+    const mcu_pin_obj_t *right_channel_pin = validate_is_free_pin_or_none(args[ARG_right_channel].u_obj);
-    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);
-    }
 
     // create AudioOut object from the given pin
     audioio_audioout_obj_t *self = m_new_obj(audioio_audioout_obj_t);

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;
+    const mcu_pin_obj_t *left_channel_pin = validate_is_free_pin(args[ARG_left_channel].u_obj);
-    assert_pin(left_channel_obj, false);
+    const mcu_pin_obj_t *right_channel_pin = validate_is_free_pin_or_none(args[ARG_right_channel].u_obj)
-    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);
-    }
 
     // create AudioOut object from the given pin
     audiopwmio_pwmaudioout_obj_t *self = m_new_obj(audiopwmio_pwmaudioout_obj_t);

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 = validate_is_free_pin(args[ARG_scl].u_obj);
-    const mcu_pin_obj_t* scl = MP_OBJ_TO_PTR(args[ARG_scl].u_obj);
+    const mcu_pin_obj_t* sda = validate_is_free_pin(args[ARG_sda].u_obj);
-    const mcu_pin_obj_t* sda = MP_OBJ_TO_PTR(args[ARG_sda].u_obj);
 
     bitbangio_i2c_obj_t *self = m_new_obj(bitbangio_i2c_obj_t);
     self->base.type = &bitbangio_i2c_type;

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);
+    const mcu_pin_obj_t* pin = validate_is_free_pin(args[ARG_pin].u_obj);
-    assert_pin_free(pin);
 
     bitbangio_onewire_obj_t *self = m_new_obj(bitbangio_onewire_obj_t);
     self->base.type = &bitbangio_onewire_type;

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);
+    const mcu_pin_obj_t* clock = validate_is_free_pin(args[ARG_clock].u_obj);
-    assert_pin(args[ARG_MISO].u_obj, true);
+    const mcu_pin_obj_t* mosi = validate_is_free_pin_or_none(args[ARG_MOSI].u_obj);
-    const mcu_pin_obj_t* clock = MP_OBJ_TO_PTR(args[ARG_clock].u_obj);
+    const mcu_pin_obj_t* miso = validate_is_free_pin_or_none(args[ARG_MISO].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);
 
     bitbangio_spi_obj_t *self = m_new_obj(bitbangio_spi_obj_t);
     self->base.type = &bitbangio_spi_type;

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 = validate_is_free_pin(args[ARG_scl].u_obj);
-    const mcu_pin_obj_t* scl = MP_OBJ_TO_PTR(args[ARG_scl].u_obj);
+    const mcu_pin_obj_t* sda = validate_is_free_pin(args[ARG_sda].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);
     common_hal_busio_i2c_construct(self, scl, sda, args[ARG_frequency].u_int, args[ARG_timeout].u_int);
     return (mp_obj_t)self;
 }

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 = validate_is_free_pin(args[ARG_pin].u_obj);
-    const mcu_pin_obj_t* pin = MP_OBJ_TO_PTR(args[ARG_pin].u_obj);
-    assert_pin_free(pin);
 
     busio_onewire_obj_t *self = m_new_obj(busio_onewire_obj_t);
     self->base.type = &busio_onewire_type;

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);
+    const mcu_pin_obj_t* clock = validate_is_free_pin(args[ARG_clock].u_obj);
-    assert_pin(args[ARG_MISO].u_obj, true);
+    const mcu_pin_obj_t* mosi = validate_is_free_pin_or_none(args[ARG_MOSI].u_obj);
-    const mcu_pin_obj_t* clock = MP_OBJ_TO_PTR(args[ARG_clock].u_obj);
+    const mcu_pin_obj_t* miso = validate_is_free_pin_or_none(args[ARG_MISO].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);
     common_hal_busio_spi_construct(self, clock, mosi, miso);
-    return (mp_obj_t)self;
+    return MP_OBJ_FROM_PTR(self);
 }
 
 //|   .. method:: deinit()

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 = validate_is_free_pin_or_none(args[ARG_rx].u_obj);
-    const mcu_pin_obj_t* rx = MP_OBJ_TO_PTR(args[ARG_rx].u_obj);
+    const mcu_pin_obj_t* tx = validate_is_free_pin_or_none(args[ARG_tx].u_obj);
-    assert_pin_free(rx);
 
-    assert_pin(args[ARG_tx].u_obj, true);
+    if ( (tx == NULL) && (rx == NULL) ) {
-    const mcu_pin_obj_t* tx = MP_OBJ_TO_PTR(args[ARG_tx].u_obj);
+        mp_raise_ValueError(translate("tx and rx cannot both be None"));
-    assert_pin_free(tx);
+    }
 
     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 bool rs485_invert = args[ARG_rs485_invert].u_bool;
-
-    const mcu_pin_obj_t* rs485_dir = args[ARG_rs485_dir].u_obj;
-    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,

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 = validate_is_free_pin(args[0]);
-    mcu_pin_obj_t *pin = MP_OBJ_TO_PTR(args[0]);
-    assert_pin_free(pin);
     common_hal_digitalio_digitalinout_construct(self, pin);
 
-    return (mp_obj_t)self;
+    return MP_OBJ_FROM_PTR(self);
 }
 
 //|   .. method:: deinit()

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;
+    const mcu_pin_obj_t* backlight_pin = validate_is_free_pin_or_none(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);
-    }
 
     mp_float_t brightness = mp_obj_get_float(args[ARG_brightness].u_obj);
 

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;
+    const mcu_pin_obj_t* busy_pin = validate_is_free_pin_or_none(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);
-    }
 
     mp_int_t rotation = args[ARG_rotation].u_int;
     if (rotation % 90 != 0) {

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 = validate_is_free_pin(args[ARG_pin].u_obj);
-    mcu_pin_obj_t* pin = MP_OBJ_TO_PTR(args[ARG_pin].u_obj);
-    assert_pin_free(pin);
 
     const uint16_t capture_period = args[ARG_capture_period].u_int;
 

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);
+    const mcu_pin_obj_t* scl = validate_is_free_pin(args[ARG_scl].u_obj);
-    assert_pin(args[ARG_sda].u_obj, false);
+    const mcu_pin_obj_t* sda = validate_is_free_pin(args[ARG_sda].u_obj);
-    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);
 
     mp_obj_iter_buf_t iter_buf;
     mp_obj_t iterable = mp_getiter(args[ARG_addresses].u_obj, &iter_buf);

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) {
+mcu_pin_obj_t *validate_is_pin(mp_obj_t obj) {
-    if ((obj != mp_const_none || !none_ok) && !MP_OBJ_IS_TYPE(obj, &mcu_pin_type)) {
+    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) {

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);

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 = validate_is_free_pin(args[ARG_clkpin].u_obj);
-    const mcu_pin_obj_t* clkpin = MP_OBJ_TO_PTR(args[ARG_clkpin].u_obj);
+    const mcu_pin_obj_t* datapin = validate_is_free_pin(args[ARG_datapin].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);
 
     ps2io_ps2_obj_t *self = m_new_obj(ps2io_ps2_obj_t);
     self->base.type = &ps2io_ps2_type;

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;
+    const mcu_pin_obj_t *pin = validate_is_free_pin(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);
 
     uint16_t duty_cycle = parsed_args[ARG_duty_cycle].u_int;
     uint32_t frequency = parsed_args[ARG_frequency].u_int;

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 = validate_is_free_pin(args[ARG_pin].u_obj);
-    const mcu_pin_obj_t* pin = MP_OBJ_TO_PTR(args[ARG_pin].u_obj);
-    assert_pin_free(pin);
 
     pulseio_pulsein_obj_t *self = m_new_obj(pulseio_pulsein_obj_t);
     self->base.type = &pulseio_pulsein_type;

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 = validate_is_free_pin(args[ARG_pin_a].u_obj);
-    const mcu_pin_obj_t* pin_a = MP_OBJ_TO_PTR(args[ARG_pin_a].u_obj);
+    const mcu_pin_obj_t* pin_b = validate_is_free_pin(args[ARG_pin_b].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);
 
     rotaryio_incrementalencoder_obj_t *self = m_new_obj(rotaryio_incrementalencoder_obj_t);
     self->base.type = &rotaryio_incrementalencoder_type;

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];
+    const mcu_pin_obj_t *pin = validate_is_free_pin(args[0]);
-    assert_pin(pin_obj, false);
-    const mcu_pin_obj_t *pin = MP_OBJ_TO_PTR(pin_obj);
-    assert_pin_free(pin);
 
     touchio_touchin_obj_t *self = m_new_obj(touchio_touchin_obj_t);
     self->base.type = &touchio_touchin_type;

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);
+    const mcu_pin_obj_t *cs = validate_is_free_pin(args[ARG_cs].u_obj);
-    assert_pin(args[ARG_rst].u_obj, true); // may be NULL
+    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;
 }

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);
@@ -55,7 +55,7 @@ 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) {