1 files changed, 96 insertions, 0 deletions
diff --git a/ports/stm32f4/common-hal/neopixel_write/__init__.c b/ports/stm32f4/common-hal/neopixel_write/__init__.c
new file mode 100644
index 000000000..fd46825d0
--- /dev/null
+++ b/ports/stm32f4/common-hal/neopixel_write/__init__.c
@@ -0,0 +1,96 @@
+/*
+ * This file is part of the MicroPython project, http://micropython.org/
+ *
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2019 Lucian Copeland for Adafruit Industries
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy
+ * of this software and associated documentation files (the "Software"), to deal
+ * in the Software without restriction, including without limitation the rights
+ * to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+ * copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in
+ * all copies or substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+ * IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+ * FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+ * AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+ * LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+ * THE SOFTWARE.
+ */
+
+#include "py/mphal.h"
+#include "shared-bindings/neopixel_write/__init__.h"
+
+#include "tick.h"
+#include "common-hal/microcontroller/Pin.h"
+#include "stm32f4xx_hal.h"
+#include "stm32f4xx_ll_gpio.h"
+
+uint64_t next_start_tick_ms = 0;
+uint32_t next_start_tick_us = 1000;
+
+//sysclock divisors
+#define MAGIC_800_INT  900000  // ~1.11 us  -> 1.2  field
+#define MAGIC_800_T0H  2800000  // ~0.36 us -> 0.44 field
+#define MAGIC_800_T1H  1350000  // ~0.74 us -> 0.84 field
+
+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;
+    uint32_t start = 0;
+    uint32_t cyc = 0;
+
+    //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
+    uint32_t sys_freq = HAL_RCC_GetSysClockFreq();
+    uint32_t interval = sys_freq/MAGIC_800_INT;
+    uint32_t t0 = (sys_freq/MAGIC_800_T0H);
+    uint32_t t1 = (sys_freq/MAGIC_800_T1H);
+
+    // This must be called while interrupts are on in case we're waiting for a
+    // future ms tick.
+    wait_until(next_start_tick_ms, next_start_tick_us);
+
+    GPIO_TypeDef * p_port = pin_port(digitalinout->pin->port);
+    uint32_t p_mask = pin_mask(digitalinout->pin->number);
+
+    __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(;;) {
+        start = DWT->CYCCNT;
+        LL_GPIO_SetOutputPin(p_port, p_mask);
+        cyc = (pix & mask) ? t1 : t0;
+        while(DWT->CYCCNT - start < cyc);
+        LL_GPIO_ResetOutputPin(p_port, p_mask);
+        if(!(mask >>= 1)) {
+            if(p >= end) break;
+            pix       = *p++;
+            mask = 0x80;
+        }
+        while(DWT->CYCCNT - start < interval); //wait for interval to finish
+    }
+
+    // Enable interrupts again
+    __enable_irq();
+
+    // Update the next start.
+    current_tick(&next_start_tick_ms, &next_start_tick_us);
+    if (next_start_tick_us < 100) {
+        next_start_tick_ms += 1;
+        next_start_tick_us = 100 - next_start_tick_us;
+    } else {
+        next_start_tick_us -= 100;
+    }
+}