esp8266: Add esp.neopixel_write function to bit-bang WS2812 data.

1 files changed, 64 insertions, 0 deletions

diff --git a/esp8266/espneopixel.c b/esp8266/espneopixel.c
new file mode 100644
index 0000000000..26776f025e
--- /dev/null
+++ b/esp8266/espneopixel.c
@@ -0,0 +1,64 @@
+// Original version from https://github.com/adafruit/Adafruit_NeoPixel
+// Modifications by dpgeorge to support auto-CPU-frequency detection
+
+// This is a mash-up of the Due show() code + insights from Michael Miller's
+// ESP8266 work for the NeoPixelBus library: github.com/Makuna/NeoPixelBus
+// Needs to be a separate .c file to enforce ICACHE_RAM_ATTR execution.
+
+#include "c_types.h"
+#include "eagle_soc.h"
+#include "user_interface.h"
+#include "espneopixel.h"
+
+#define NEO_KHZ400 (1)
+
+static uint32_t _getCycleCount(void) __attribute__((always_inline));
+static inline uint32_t _getCycleCount(void) {
+  uint32_t ccount;
+  __asm__ __volatile__("rsr %0,ccount":"=a" (ccount));
+  return ccount;
+}
+
+void /*ICACHE_RAM_ATTR*/ esp_neopixel_write(uint8_t pin, uint8_t *pixels, uint32_t numBytes, bool is800KHz) {
+
+  uint8_t *p, *end, pix, mask;
+  uint32_t t, time0, time1, period, c, startTime, pinMask;
+
+  pinMask   = 1 << pin;
+  p         =  pixels;
+  end       =  p + numBytes;
+  pix       = *p++;
+  mask      = 0x80;
+  startTime = 0;
+
+  uint32_t fcpu = system_get_cpu_freq() * 1000000;
+
+#ifdef NEO_KHZ400
+  if(is800KHz) {
+#endif
+    time0  = fcpu / 2500000; // 0.4us
+    time1  = fcpu / 1250000; // 0.8us
+    period = fcpu /  800000; // 1.25us per bit
+#ifdef NEO_KHZ400
+  } else { // 400 KHz bitstream
+    time0  = fcpu / 2000000; // 0.5uS
+    time1  = fcpu /  833333; // 1.2us
+    period = fcpu /  400000; // 2.5us per bit
+  }
+#endif
+
+  for(t = time0;; t = time0) {
+    if(pix & mask) t = time1;                             // Bit high duration
+    while(((c = _getCycleCount()) - startTime) < period); // Wait for bit start
+    GPIO_REG_WRITE(GPIO_OUT_W1TS_ADDRESS, pinMask);       // Set high
+    startTime = c;                                        // Save start time
+    while(((c = _getCycleCount()) - startTime) < t);      // Wait high duration
+    GPIO_REG_WRITE(GPIO_OUT_W1TC_ADDRESS, pinMask);       // Set low
+    if(!(mask >>= 1)) {                                   // Next bit/byte
+      if(p >= end) break;
+      pix  = *p++;
+      mask = 0x80;
+    }
+  }
+  while((_getCycleCount() - startTime) < period); // Wait for last bit
+}