WS2801LED Arduino Sketch

This sketch is used by Exercise: WS2801 RGB LED SPI Module.

Full Source Code

The full code is all in one file WS2801LED.ino.

 1// -*- mode:c++; -*-
 2/// @file WS2801LED.ino
 3/// 
 4/// @brief Example for driving several WS2801 RGB LED modules over SPI on an Arduino UNO.
 5///
 6/// @author Garth Zeglin
 7/// @date 2014-09-13
 8///
 9/// @remarks The WS2801 LED driver has three current controlled LED outputs with
10/// 8-bit precision (256 levels).  It is controlled over SPI by sending 24 bits
11/// of pixel data at up to 25MHz rate.  Additional data is then relayed to the output
12/// SPI pins to feed daisy-chained drivers.  Once the bus is quiescent for 500
13/// microseconds, the data is applied to the outputs and the chip is ready to
14/// receive more values.
15///
16/// So a large number of of drivers can be fed on each channel, limited only by
17/// the overall refresh rate.  But the data must be fed without interruption to
18/// avoid prematurely ending the cycle.
19///
20/// The actual color data sequence depends upon the wiring of the module; on one
21/// particular strip light tested the actual sequence was blue-red-green.
22///
23/// Note that the relay scheme means that first three bytes output feed the
24/// first module, the second three the second module, etc.  In other words, the
25/// strand is not a shift register.  Extra data has no effect.
26
27/// This sketch assumes the following electrical connections from the Arduino to
28/// the first module in a chain:
29
30/// PIN11 (MOSI)  ->  DAT
31/// PIN13 (SCK)   ->  CLK
32/// GND           ->  GND
33
34// Include the SPI library.
35#include <SPI.h>
36
37
38void setup() 
39{
40  SPI.begin();  // initialize SPI hardware
41}
42
43void loop() 
44{
45  static int cycle = 0;
46
47  // on each iteration, shift out RGB data for several pixels, then delay to allow the device to update.
48  for (int pixel = 0; pixel < 3; pixel++ ) {
49    uint8_t red   =  3 * (cycle + 32*pixel);
50    uint8_t green =  5 * (cycle + 32*pixel);
51    uint8_t blue  =  7 * (cycle + 32*pixel);
52    SPI.transfer( blue  );
53    SPI.transfer( red   );
54    SPI.transfer( green );
55  }
56  
57  delay(1);  // delay 1 millisecond to allow outputs to update
58  cycle++;   // update the overall animation
59
60  // add a delay to control the overall frame rate
61  delay(20); 
62}