ESP8266 implementation of WS2811 LED Strip protocol (without I²S / DMA)

ws2811.c

// System
#include <ets_sys.h>
#include <osapi.h>
#include <gpio.h>
#include <os_type.h>
#include <user_interface.h>

// Project
#include "ws2811.h"

#define CPU_FREQ 26000000
#define CYCLES_PER_US CPU_FREQ/(2*1000000)

void __attribute__((optimize("O2"))) ws2811_putbit(bool bit) {
	uint8_t i;
	if (bit) {
		i = 0.6 * CYCLES_PER_US;
		while (i--) GPIO_REG_WRITE(GPIO_OUT_W1TS_ADDRESS, BIT(WSGPIO));
		i = 0.65 * CYCLES_PER_US;
		while (i--) GPIO_REG_WRITE(GPIO_OUT_W1TC_ADDRESS, BIT(WSGPIO));
	} else {
		i = 0.25 * CYCLES_PER_US;
		while (i--) GPIO_REG_WRITE(GPIO_OUT_W1TS_ADDRESS, BIT(WSGPIO));
		i = 1.0 * CYCLES_PER_US;
		while (i--) GPIO_REG_WRITE(GPIO_OUT_W1TC_ADDRESS, BIT(WSGPIO));
	}
}

void ICACHE_FLASH_ATTR ws2811_put(uint8_t pxbuf[][3], uint16_t pixels)
{
	PIN_PULLUP_DIS(WSGPIO_MUX);
	PIN_FUNC_SELECT(WSGPIO_MUX, WSGPIO_FUNC);
	CLEAR_PERI_REG_MASK(WSGPIO_MUX, BIT6);
	GPIO_OUTPUT_SET(GPIO_ID_PIN(WSGPIO), 0);

	os_delay_us(1);
	uint8_t px;

	ets_intr_lock();
	for (px = 0; px < pixels * 3; ++px) {
		ws2811_putbit(pxbuf[px / 3][px % 3] & (1<<7));
		ws2811_putbit(pxbuf[px / 3][px % 3] & (1<<6));
		ws2811_putbit(pxbuf[px / 3][px % 3] & (1<<5));
		ws2811_putbit(pxbuf[px / 3][px % 3] & (1<<4));
		ws2811_putbit(pxbuf[px / 3][px % 3] & (1<<3));
		ws2811_putbit(pxbuf[px / 3][px % 3] & (1<<2));
		ws2811_putbit(pxbuf[px / 3][px % 3] & (1<<1));
		ws2811_putbit(pxbuf[px / 3][px % 3] & (1<<0));
	}
	ets_intr_unlock();
}

ws2811.h

/**
 * Driver for both WS2811 (in fast mode, as used in plastic led pixels)
 * and WS2812B (as used in LED Strips).
 */

#ifndef _WS2811_H
#define _WS2811_H

#define WSGPIO 14
#define WSGPIO_MUX PERIPHS_IO_MUX_MTMS_U
#define WSGPIO_FUNC FUNC_GPIO14

void ws2811_put(uint8_t buffer[][3], uint16_t pixels);

#endif