diff --git a/ports/stm32f4/boards/meowbit_v121/pins.c b/ports/stm32f4/boards/meowbit_v121/pins.c
index 0cdbefd59b..1489c23f1c 100644
--- a/ports/stm32f4/boards/meowbit_v121/pins.c
+++ b/ports/stm32f4/boards/meowbit_v121/pins.c
@@ -60,6 +60,6 @@ STATIC const mp_rom_map_elem_t board_module_globals_table[] = {
     { MP_ROM_QSTR(MP_QSTR_P0), MP_ROM_PTR(&pin_PA00) },
     { MP_ROM_QSTR(MP_QSTR_P3), MP_ROM_PTR(&pin_PB00) },
 
-    { MP_ROM_QSTR(MP_QSTR_INTERNAL_SPI), MP_ROM_PTR(&spi) },
+    { MP_ROM_QSTR(MP_QSTR_INTERNAL_SPI), MP_ROM_PTR(&supervisor_flash_spi_bus) },
 };
 MP_DEFINE_CONST_DICT(board_module_globals, board_module_globals_table);
diff --git a/ports/stm32f4/common-hal/pulseio/PWMOut.c b/ports/stm32f4/common-hal/pulseio/PWMOut.c
index 000325be30..29376691bb 100644
--- a/ports/stm32f4/common-hal/pulseio/PWMOut.c
+++ b/ports/stm32f4/common-hal/pulseio/PWMOut.c
@@ -68,9 +68,9 @@ STATIC uint32_t timer_get_source_freq(uint32_t tim_id) {
 }
 
 STATIC uint32_t timer_get_internal_duty(uint16_t duty, uint32_t period) {
-    //duty cycle is (0xFFFF - duty)/0xFFFF fraction x (number of pulses per period)
+    //duty cycle is duty/0xFFFF fraction x (number of pulses per period)
     //Note that pulses are inverted, so duty cycle is inverted
-    return ((0xFFFF - duty)*period) / ((1 << 16) - 1);
+    return (duty*period) / ((1 << 16) - 1);
 }
 
 STATIC void timer_get_optimal_divisors(uint32_t*period, uint32_t*prescaler, 
@@ -203,7 +203,7 @@ pwmout_result_t common_hal_pulseio_pwmout_construct(pulseio_pwmout_obj_t* self,
     //Channel/PWM init
     self->chan_handle.OCMode = TIM_OCMODE_PWM1;
     self->chan_handle.Pulse = timer_get_internal_duty(duty, period);
-    self->chan_handle.OCPolarity = TIM_OCPOLARITY_LOW;
+    self->chan_handle.OCPolarity = TIM_OCPOLARITY_HIGH;
     self->chan_handle.OCFastMode = TIM_OCFAST_DISABLE;
     self->chan_handle.OCNPolarity = TIM_OCNPOLARITY_LOW; // needed for TIM1 and TIM8
     self->chan_handle.OCIdleState = TIM_OCIDLESTATE_SET; // needed for TIM1 and TIM8
diff --git a/shared-module/displayio/__init__.c b/shared-module/displayio/__init__.c
index 8d9f148834..efa61265e6 100644
--- a/shared-module/displayio/__init__.c
+++ b/shared-module/displayio/__init__.c
@@ -104,7 +104,7 @@ void reset_displays(void) {
                     }
                 #endif
                 #ifdef BOARD_USE_INTERNAL_SPI
-                    if (original_spi == (mp_obj_t)(&spi)) {
+                    if (original_spi == (mp_obj_t)(&supervisor_flash_spi_bus)) {
                         continue;
                     }
                 #endif
diff --git a/supervisor/shared/external_flash/spi_flash.c b/supervisor/shared/external_flash/spi_flash.c
index 12888f2d33..67e64c970e 100644
--- a/supervisor/shared/external_flash/spi_flash.c
+++ b/supervisor/shared/external_flash/spi_flash.c
@@ -36,33 +36,33 @@
 #include "py/mpconfig.h"
 
 digitalio_digitalinout_obj_t cs_pin;
-busio_spi_obj_t spi;
+busio_spi_obj_t supervisor_flash_spi_bus;
 
 const external_flash_device* flash_device;
 uint32_t spi_flash_baudrate;
 
 // Enable the flash over SPI.
 static void flash_enable(void) {
-    while (!common_hal_busio_spi_try_lock(&spi)) {}
+    while (!common_hal_busio_spi_try_lock(&supervisor_flash_spi_bus)) {}
     common_hal_digitalio_digitalinout_set_value(&cs_pin, false);
 }
 
 // Disable the flash over SPI.
 static void flash_disable(void) {
     common_hal_digitalio_digitalinout_set_value(&cs_pin, true);
-    common_hal_busio_spi_unlock(&spi);
+    common_hal_busio_spi_unlock(&supervisor_flash_spi_bus);
 }
 
 static bool transfer(uint8_t* command, uint32_t command_length, uint8_t* data_in, uint8_t* data_out, uint32_t data_length) {
     flash_enable();
-    bool status = common_hal_busio_spi_write(&spi, command, command_length);
+    bool status = common_hal_busio_spi_write(&supervisor_flash_spi_bus, command, command_length);
     if (status) {
         if (data_in != NULL && data_out != NULL) {
-            status = common_hal_busio_spi_transfer(&spi, data_out, data_in, data_length);
+            status = common_hal_busio_spi_transfer(&supervisor_flash_spi_bus, data_out, data_in, data_length);
         } else if (data_out != NULL) {
-            status = common_hal_busio_spi_read(&spi, data_out, data_length, 0xff);
+            status = common_hal_busio_spi_read(&supervisor_flash_spi_bus, data_out, data_length, 0xff);
         } else if (data_in != NULL) {
-            status = common_hal_busio_spi_write(&spi, data_in, data_length);
+            status = common_hal_busio_spi_write(&supervisor_flash_spi_bus, data_in, data_length);
         }
     }
     flash_disable();
@@ -103,10 +103,10 @@ bool spi_flash_write_data(uint32_t address, uint8_t* data, uint32_t data_length)
     // Write the SPI flash write address into the bytes following the command byte.
     address_to_bytes(address, request + 1);
     flash_enable();
-    common_hal_busio_spi_configure(&spi, spi_flash_baudrate, 0, 0, 8);
-    bool status = common_hal_busio_spi_write(&spi, request, 4);
+    common_hal_busio_spi_configure(&supervisor_flash_spi_bus, spi_flash_baudrate, 0, 0, 8);
+    bool status = common_hal_busio_spi_write(&supervisor_flash_spi_bus, request, 4);
     if (status) {
-        status = common_hal_busio_spi_write(&spi, data, data_length);
+        status = common_hal_busio_spi_write(&supervisor_flash_spi_bus, data, data_length);
     }
     flash_disable();
     return status;
@@ -122,10 +122,10 @@ bool spi_flash_read_data(uint32_t address, uint8_t* data, uint32_t data_length)
     // Write the SPI flash write address into the bytes following the command byte.
     address_to_bytes(address, request + 1);
     flash_enable();
-    common_hal_busio_spi_configure(&spi, spi_flash_baudrate, 0, 0, 8);
-    bool status = common_hal_busio_spi_write(&spi, request, command_length);
+    common_hal_busio_spi_configure(&supervisor_flash_spi_bus, spi_flash_baudrate, 0, 0, 8);
+    bool status = common_hal_busio_spi_write(&supervisor_flash_spi_bus, request, command_length);
     if (status) {
-        status = common_hal_busio_spi_read(&spi, data, data_length, 0xff);
+        status = common_hal_busio_spi_read(&supervisor_flash_spi_bus, data, data_length, 0xff);
     }
     flash_disable();
     return status;
@@ -140,9 +140,9 @@ void spi_flash_init(void) {
     common_hal_digitalio_digitalinout_switch_to_output(&cs_pin, true, DRIVE_MODE_PUSH_PULL);
     common_hal_digitalio_digitalinout_never_reset(&cs_pin);
 
-    spi.base.type = &busio_spi_type;
-    common_hal_busio_spi_construct(&spi, SPI_FLASH_SCK_PIN, SPI_FLASH_MOSI_PIN, SPI_FLASH_MISO_PIN);
-    common_hal_busio_spi_never_reset(&spi);
+    supervisor_flash_spi_bus.base.type = &busio_spi_type;
+    common_hal_busio_spi_construct(&supervisor_flash_spi_bus, SPI_FLASH_SCK_PIN, SPI_FLASH_MOSI_PIN, SPI_FLASH_MISO_PIN);
+    common_hal_busio_spi_never_reset(&supervisor_flash_spi_bus);
 }
 
 void spi_flash_init_device(const external_flash_device* device) {
diff --git a/supervisor/spi_flash_api.h b/supervisor/spi_flash_api.h
index b477308bab..f59346e25a 100644
--- a/supervisor/spi_flash_api.h
+++ b/supervisor/spi_flash_api.h
@@ -33,7 +33,7 @@
 
 #include "shared-bindings/busio/SPI.h"
 
-extern busio_spi_obj_t spi; //Used to share SPI bus on some boards
+extern busio_spi_obj_t supervisor_flash_spi_bus; //Used to share SPI bus on some boards
 
 // This API is implemented for both normal SPI peripherals and QSPI peripherals.