Merge pull request #2350 from hierophect/stm32-neopixel-fix

Fix for neopixels on <100MHz STM32 boards

Author: tannewt

ports/stm32f4/common-hal/digitalio/DigitalInOut.c

@@ -47,7 +47,7 @@ digitalinout_result_t common_hal_digitalio_digitalinout_construct(
     GPIO_InitStruct.Pin = pin_mask(self->pin->number);
     GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
     GPIO_InitStruct.Pull = GPIO_NOPULL;
-    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
+    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
     HAL_GPIO_Init(pin_port(self->pin->port), &GPIO_InitStruct);
 
     return DIGITALINOUT_OK;
@@ -73,7 +73,7 @@ void common_hal_digitalio_digitalinout_switch_to_input(
     GPIO_InitStruct.Pin = pin_mask(self->pin->number);
     GPIO_InitStruct.Mode = GPIO_MODE_INPUT;
     GPIO_InitStruct.Pull = GPIO_NOPULL;
-    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_LOW;
+    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
     HAL_GPIO_Init(pin_port(self->pin->port), &GPIO_InitStruct);
 
     common_hal_digitalio_digitalinout_set_pull(self, pull);
@@ -114,7 +114,7 @@ void common_hal_digitalio_digitalinout_set_drive_mode(
     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_LOW;
+    GPIO_InitStruct.Speed = GPIO_SPEED_FREQ_VERY_HIGH;
     HAL_GPIO_Init(pin_port(self->pin->port), &GPIO_InitStruct);
 }
 

ports/stm32f4/common-hal/neopixel_write/__init__.c

@@ -28,6 +28,8 @@
 #include "shared-bindings/neopixel_write/__init__.h"
 
 #include "tick.h"
+#include "py/mperrno.h"
+#include "py/runtime.h"
 #include "common-hal/microcontroller/Pin.h"
 #include "stm32f4xx_hal.h"
 #include "stm32f4xx_ll_gpio.h"
@@ -40,6 +42,9 @@ uint32_t next_start_tick_us = 1000;
 #define MAGIC_800_T0H  2800000  // ~0.36 us -> 0.44 field
 #define MAGIC_800_T1H  1350000  // ~0.74 us -> 0.84 field
 
+#pragma GCC push_options
+#pragma GCC optimize ("Os")
+
 void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout, uint8_t *pixels, 
                                 uint32_t numBytes) {
     uint8_t *p = pixels, *end = p + numBytes, pix = *p++, mask = 0x80;
@@ -48,7 +53,7 @@ void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout
 
     //assumes 800_000Hz frequency
     //Theoretical values here are 800_000 -> 1.25us, 2500000->0.4us, 1250000->0.8us
-    //But they don't work, possibly due to bad optimization? Use tested magic values instead
+    //TODO: try to get dynamic weighting working again
     uint32_t sys_freq = HAL_RCC_GetSysClockFreq();
     uint32_t interval = sys_freq/MAGIC_800_INT;
     uint32_t t0 = (sys_freq/MAGIC_800_T0H);
@@ -63,23 +68,22 @@ void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout
 
     __disable_irq();
     // Enable DWT in debug core. Useable when interrupts disabled, as opposed to Systick->VAL
-    //ITM->LAR = 0xC5ACCE55; //this should be required but isn't
     CoreDebug->DEMCR |= CoreDebug_DEMCR_TRCENA_Msk;
     DWT->CTRL |= DWT_CTRL_CYCCNTENA_Msk;
     DWT->CYCCNT = 0;
 
     for(;;) {
+        cyc = (pix & mask) ? t1 : t0;
         start = DWT->CYCCNT;
         LL_GPIO_SetOutputPin(p_port, p_mask);
-        cyc = (pix & mask) ? t1 : t0;
-        while(DWT->CYCCNT - start < cyc);
+        while((DWT->CYCCNT - start) < cyc);
         LL_GPIO_ResetOutputPin(p_port, p_mask);
+        while((DWT->CYCCNT - start) < interval);
         if(!(mask >>= 1)) {
             if(p >= end) break;
             pix       = *p++;
             mask = 0x80;
         }
-        while(DWT->CYCCNT - start < interval); //wait for interval to finish
     }
 
     // Enable interrupts again
@@ -94,3 +98,5 @@ void common_hal_neopixel_write (const digitalio_digitalinout_obj_t* digitalinout
         next_start_tick_us -= 100;
     }
 }
+
+#pragma GCC pop_options