CJMCU-8*8 RGB LED matrix example added

Author: jandelgado

.gitignore

@@ -0,0 +1,3 @@
+*~
+libraries
+libraries/*

README.md

@@ -1,10 +1,27 @@
 # arduino
-Arduino libraries and sketches
+
+Arduino libraries and sketches.
+
+
+<!-- vim-markdown-toc GFM -->
+
+* [Libraries](#libraries)
+    * [JLed](#jled)
+    * [log4arduino](#log4arduino)
+* [Sketches](#sketches)
+    * [Interfacing SSD1306 based OLED displays (SPI)](#interfacing-ssd1306-based-oled-displays-spi)
+    * [Colorduino RGB matrix driver](#colorduino-rgb-matrix-driver)
+    * [CMJMCU-8x8 RGB matix](#cmjmcu-8x8-rgb-matix)
+
+<!-- vim-markdown-toc -->
 
 ## Libraries
 
 ### JLed
-JLed is an Arduino library to control LEDs. It uses a non-blocking approach and can control LEDs in simple (on/off) and complex (blinking, breathing) ways in a time-driven manner.
+
+JLed is an Arduino library to control LEDs. It uses a non-blocking approach and
+can control LEDs in simple (on/off) and complex (blinking, breathing) ways in a
+time-driven manner.
 
 * https://github.com/jandelgado/jled
 
@@ -16,12 +33,27 @@ A lightweight, no-frills logging library for Arduino & friends.
 
 ## Sketches
 
-### interfacing SSD1306 based OLED displays (SPI)
+### Interfacing SSD1306 based OLED displays (SPI)
+
+<img alt="ssd1306" width=256 src="images/ssd1306.jpg">
 
-* ssd1306_sample_adafruit - sample code for ssd1306 based oled display. see [wiki](http://github.com/pacodelgado/arduino/wiki/SSD1306-based-OLED-connected-to-Arduino) for detailed information
-*  ssd1306_sample_u8g - sample code for ssd1306 based oled display. see [wiki](http://github.com/pacodelgado/arduino/wiki/SSD1306-based-OLED-connected-to-Arduino) for detailed information
+* [ssd1306_sample_adafruit](ssd1306_sample_adafruit) - sample code for ssd1306 based oled display. see [wiki](http://github.com/jandelgado/arduino/wiki/SSD1306-based-OLED-connected-to-Arduino) for detailed information
+* [ssd1306_sample_u8g](ssd1306_sample_u8g) - sample code for ssd1306 based oled display. see [wiki](http://github.com/jandelgado/arduino/wiki/SSD1306-based-OLED-connected-to-Arduino) for detailed information
 
 
 ### Colorduino RGB matrix driver
 
-* see [wiki](https://github.com/pacodelgado/arduino/wiki/Colorduino) for detailed information
+Driver for 8x8 RGB LED matrix.
+
+<img alt="Colorduino" width=256 src="images/colorduino.JPG">
+
+* see [wiki](https://github.com/jandelgado/arduino/wiki/Colorduino) for detailed information
+
+
+### CMJMCU-8x8 RGB matix
+
+An 8x8 LED RGB matrix based on WS2812 "NeoPixels".
+
+<img alt="CJMCU-8*8" width=256 src="images/cjmcu-8x8/cjmcu.jpg">
+
+* see [README of example sketch](cjmcu_8x8_sample/README.md) for detailed information.

cjmcu_8x8_sample/README.md

@@ -0,0 +1,32 @@
+# CJMCU-8*8 LED RGB Matrix
+
+<img alt="CJMCU-8*8" width=480 src="../images/cjmcu-8x8/cjmcu.jpg">
+
+I recently got some of those `CMCJU-8*8` labeled LED RGB Matrix boards.
+According to what is printed on the boards, they are opposed to be built
+up on `WS2812B` RGB "Neopixel" LEDs. Connecting the matrix to an Arduino however,
+I had no luck at all on my first attempt. Later I found that these PCBs were
+totally misleadingly labeled:
+
+* `DIN` and `DOUT` labels are exchanged (!)
+* the board uses `WS2812` LEDs, which use the WS2811 driver IC (but is labeled as
+  `WS2812B`)
+
+| Front | Back |
+| ----- | ---- |
+| ![CJMCU-8*8 front](../images/cjmcu-8x8/cjmcu_front.jpg) | ![CJMCU-8*8 back](../images/cjmcu-8x8/cjmcu_back.jpg) |
+
+Knowing that, I could get the board up and running using the FastLED library
+without problem. [See the Demo sketch for an example](cjmcu_8x8_sample.ino).
+The sketch assumes the CJMCU board is connected to pin D9 of an Arduino.
+
+Since the WS2812 (which is an WS2811 driver IC packaged with a LED) and the WS2812B
+use the same protocol, the difference in type make no difference in interfacing
+the LEDs with e.g. the [FastLED library](https://github.com/FastLED/FastLED).
+
+## Spot the difference
+
+The WS2812 uses a 6 pin package. So if your LEDs have 6 pins instead of 4,
+then chances are your PCB is populated with WS2812 LEDs.
+
+![ws2812 detail](../images/cjmcu-8x8/ws2812_detail.jpg)

cjmcu_8x8_sample/cjmcu_8x8_sample.ino

@@ -0,0 +1,43 @@
+// Demo for CJMCU-8*8 LED RGB Matrix. Demo assumes CJMCU connected
+// to an Arduino nano on PIN D9
+// Jan Delgado 2018
+#include <FastLED.h>
+
+// LED configutration
+#define LED_TYPE WS2812B   // type of LED in use. CJMCU works with
+                           // WS2811,WS2812,WS2812B (compatible)
+
+constexpr auto LED_DT = 9; // Pin WS2812 Data in (DIN) is connected to
+constexpr auto COLOR_ORDER = GRB;  
+constexpr auto NUM_LEDS = 64;
+constexpr auto SPEED_MS = 50;
+
+CRGB leds[NUM_LEDS];
+
+void setup() {
+
+    LEDS.addLeds<LED_TYPE, LED_DT, COLOR_ORDER>(leds, NUM_LEDS);
+    FastLED.setBrightness(128);
+
+    // FastLED 2.1 Power management set at 5V, 500mA
+    set_max_power_in_volts_and_milliamps(5, 500);
+    CRGB cols[] = {CRGB::Red, CRGB::Green, CRGB::Blue};
+
+    for(auto c : cols) {
+      for(auto i = 0; i<NUM_LEDS; i++ ) {
+        leds[i] = c;
+      }
+      FastLED.show();
+      delay(1000);
+    }
+}
+
+void loop() {
+    static int hue = 0;
+    static int delta_hue = 4;
+
+    EVERY_N_MILLISECONDS(SPEED_MS) {
+        fill_rainbow(leds, NUM_LEDS, hue++, delta_hue);
+    }
+    show_at_max_brightness_for_power();
+}