ws2812_i2s: WS2812 leds driver implementation using i2s_dma library

extras/ws2812_i2s/ws2812_i2s.h

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+/**
+ * The MIT License (MIT)
+ *
+ * Copyright (c) 2016 sheinz (https://github.com/sheinz)
+ *
+ * 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.
+ */
+#ifndef __WS2812_I2S_H__
+#define __WS2812_I2S_H__
+
+#include <stdint.h>
+#include <stdbool.h>
+
+typedef struct {
+    uint8_t red;
+    uint8_t green;
+    uint8_t blue;
+} ws2812_pixel_t;
+
+/**
+ * Initialize i2s and dma subsystems to work with ws2812 led strip.
+ *
+ * Please note that each pixel will take 12 bytes of RAM.
+ *
+ * @param pixels_number Number of pixels in the strip.
+ */
+void ws2812_i2s_init(uint32_t pixels_number);
+
+/**
+ * Update ws2812 pixels.
+ *
+ * @param pixels Array of 'pixels_number' pixels. The array must contain all
+ * the pixels.
+ */
+void ws2812_i2s_update(ws2812_pixel_t *pixels);
+
+#endif  // __WS2812_I2S_H__