add ws2812 compatibility layer (#1947)

docs/en/modules/ws2812.md

@@ -6,6 +6,10 @@
 ws2812 is a library to handle ws2812-like led strips.
 It works at least on WS2812, WS2812b, APA104, SK6812 (RGB or RGBW).
 
+!!! note
+
+    The API on ESP32 differs from the API on ESP8266. For backwards compatibility please refer to [`lua_compat/ws2812_compat.lua`](../../../lua_compat/ws2812_compat.lua`).
+
 ## ws2812.write()
 Send data to up to 8 led strip using its native format which is generally Green,Red,Blue for RGB strips and Green,Red,Blue,White for RGBW strips.
 

lua_compat/ws2812_compat.lua

@@ -0,0 +1,74 @@
+-- ****************************************************************************
+--
+-- Compatability wrapper for mapping ESP8266's ws2812 module API to ESP32
+--
+-- Usage:
+--
+--   ws2812 = require("ws2812_compat")(pin_strip1[, pin_strip2])
+--
+--     pin_strip1: GPIO pin of first led strip, mandatory
+--     pin_strip2: GPIO pin of second led strip, optional
+--
+-- ****************************************************************************
+
+local M = {}
+
+local _pin_strip1, _pin_strip2
+local _mode
+
+local _ws2812
+
+
+-- ****************************************************************************
+-- Implement esp8266 compatability API
+--
+function M.init(mode)
+  if _pin_strip1 == nil then
+    error("gpio for data1 undefined")
+  end
+
+  if _pin_strip2 == nil and mode == M.MODE_DUAL then
+    error("gpio for data2 undefined")
+  end
+
+  _mode = mode or M.MODE_SINGLE
+end
+
+function M.write(data1, data2)
+  if _mode == nil then
+    error("call init() first")
+  end
+
+  local strip1 = {pin = _pin_strip1, data = data1}
+  local strip2
+
+  if _pin_strip2 and data2 then
+    strip2 = {pin = _pin_strip2, data = data2}
+  end
+
+  _ws2812.write(strip1, strip2)
+end
+
+return function (pin_strip1, pin_strip2)
+  -- cache built-in module
+  _ws2812 = ws2812
+  -- invalidate built-in module
+  ws2812 = nil
+
+  -- forward unchanged functions
+  M.newBuffer = _ws2812.newBuffer
+
+  -- forward constant definitions
+  M.FADE_IN        = _ws2812.FADE_IN
+  M.FADE_OUT       = _ws2812.FADE_OUT
+  M.MODE_SINGLE    = 0   -- encoding from ws2812.c
+  M.MODE_DUAL      = 1   -- encoding from ws2812.c
+  M.SHIFT_LOGICAL  = _ws2812.SHIFT_LOGICAL
+  M.SHIFT_CIRCULAR = _ws2812.SHIFT_CIRCULAR
+
+  _pin_strip1 = pin_strip1
+  _pin_strip2 = pin_strip2
+
+  return M
+end
+