Brian Daniels / WS2812

Library for the WS2812 LED Driver. Uses bit banging and nops for precise timing. Number of nops executed are configurable at run time.

Dependents:   WS2812_Example WS2812_Example_fade Lamp_03 Lamp_04 ... more

This library uses bit banging to control the LED strip. Because the mbed platform doesn't have a timer standardized that doesn't have a resolution lower a microsecond, we have to use NOPs. Also, the time it takes to toggle a GPIO pin is not consistent across platforms and it does not correlate to the system clock in any way. It is completely dependent on the platform's implementation.

I have a found the timings for a few boards. They are currently listed on the example program page below.

Import programWS2812_Example

Example for WS2812 Library

Last commit 12 Feb 2015 by Brian Daniels

When using this on a new platform, you'll need to use a logic analyzer to determine the timings.

/media/uploads/bridadan/k64f_ws2812_timing_v2.png

Above is a screenshot from a Saleae logic analyzer. You'll notice that the "1" pulse is longer than the "0" pulse. The "Data low" pulses should be consistent. The timing requirements for these pulses can be found below (Source: http://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/).

/media/uploads/bridadan/ws2812_timings.png

If you find timings for a new board you're using, please PM me or start a discussion below and I'll add it to this page!

For more on the timings and data format of the WS2812 drivers, you should read the datasheet and the article "NeoPixels Revealed: How to (not need to) generate precisely timed signals" listed below.

References:

WS2812B Datasheet: https://www.adafruit.com/datasheets/WS2812B.pdf

"NeoPixels Revealed: How to (not need to) generate precisely timed signals": http://wp.josh.com/2014/05/13/ws2812-neopixels-are-not-so-finicky-once-you-get-to-know-them/

WS2812.h@0:0b79cafcb387, 2015-02-12 (annotated)

Committer:
bridadan
Date:
Thu Feb 12 19:17:10 2015 +0000
Revision:
0:0b79cafcb387
Child:
1:aadbf08c62a2
Driver for the WS2812 LED driver. Uses bit banging and relies on nops for timing. Number of nops can be varied to potentially accommodate different platforms. Currently tested on the K64F.

Who changed what in which revision?

UserRevisionLine numberNew contents of line
bridadan 0:0b79cafcb387 1 /* Copyright (c) 2012 cstyles, MIT License
bridadan 0:0b79cafcb387 2 *
bridadan 0:0b79cafcb387 3 * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
bridadan 0:0b79cafcb387 4 * and associated documentation files (the "Software"), to deal in the Software without restriction,
bridadan 0:0b79cafcb387 5 * including without limitation the rights to use, copy, modify, merge, publish, distribute,
bridadan 0:0b79cafcb387 6 * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
bridadan 0:0b79cafcb387 7 * furnished to do so, subject to the following conditions:
bridadan 0:0b79cafcb387 8 *
bridadan 0:0b79cafcb387 9 * The above copyright notice and this permission notice shall be included in all copies or
bridadan 0:0b79cafcb387 10 * substantial portions of the Software.
bridadan 0:0b79cafcb387 11 *
bridadan 0:0b79cafcb387 12 * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
bridadan 0:0b79cafcb387 13 * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
bridadan 0:0b79cafcb387 14 * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
bridadan 0:0b79cafcb387 15 * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
bridadan 0:0b79cafcb387 16 * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
bridadan 0:0b79cafcb387 17 */
bridadan 0:0b79cafcb387 18
bridadan 0:0b79cafcb387 19 #ifndef WS2812_H
bridadan 0:0b79cafcb387 20 #define WS2812_H
bridadan 0:0b79cafcb387 21
bridadan 0:0b79cafcb387 22 #include "mbed.h"
bridadan 0:0b79cafcb387 23
bridadan 0:0b79cafcb387 24 #define WS1 0x38
bridadan 0:0b79cafcb387 25 #define WS0 0x30
bridadan 0:0b79cafcb387 26 #define SPICLK 5000000
bridadan 0:0b79cafcb387 27 #define FRAME_SIZE 24
bridadan 0:0b79cafcb387 28
bridadan 0:0b79cafcb387 29
bridadan 0:0b79cafcb387 30 //!Library for the WS2812 RGB LED with integrated controller
bridadan 0:0b79cafcb387 31 /*!
bridadan 0:0b79cafcb387 32 The WS2812 is controller that is built into a range of LEDs
bridadan 0:0b79cafcb387 33 */
bridadan 0:0b79cafcb387 34 class WS2812
bridadan 0:0b79cafcb387 35 {
bridadan 0:0b79cafcb387 36 public:
bridadan 0:0b79cafcb387 37 //!Creates an instance of the class.
bridadan 0:0b79cafcb387 38 /*!
bridadan 0:0b79cafcb387 39 Connect WS2812 address addr using digital pins
bridadan 0:0b79cafcb387 40 */
bridadan 0:0b79cafcb387 41 WS2812(PinName d, int size);
bridadan 0:0b79cafcb387 42
bridadan 0:0b79cafcb387 43 /*!
bridadan 0:0b79cafcb387 44 Destroys instance.
bridadan 0:0b79cafcb387 45 */
bridadan 0:0b79cafcb387 46 ~WS2812();
bridadan 0:0b79cafcb387 47
bridadan 0:0b79cafcb387 48 void setDelays(int zeroHigh, int zeroLow, int oneHigh, int oneLow);
bridadan 0:0b79cafcb387 49
bridadan 0:0b79cafcb387 50 void write(int buf[]);
bridadan 0:0b79cafcb387 51 void write_offsets(int buf[],int r_offset=0, int g_offset=0, int b_offset=0);
bridadan 0:0b79cafcb387 52
bridadan 0:0b79cafcb387 53 void useII(int d);
bridadan 0:0b79cafcb387 54 void setII(unsigned char II);
bridadan 0:0b79cafcb387 55
bridadan 0:0b79cafcb387 56
bridadan 0:0b79cafcb387 57
bridadan 0:0b79cafcb387 58 private:
bridadan 0:0b79cafcb387 59
bridadan 0:0b79cafcb387 60 int __size;
bridadan 0:0b79cafcb387 61 int __zeroHigh, __zeroLow, __oneHigh, __oneLow;
bridadan 0:0b79cafcb387 62 unsigned char __II;
bridadan 0:0b79cafcb387 63 int __use_II;
bridadan 0:0b79cafcb387 64 bool *__transmitBuf;
bridadan 0:0b79cafcb387 65 void __loadBuf(int buf[],int r_offset=0, int g_offset=0, int b_offset=0);
bridadan 0:0b79cafcb387 66 PinName __outPin;
bridadan 0:0b79cafcb387 67 DigitalOut __gpo;
bridadan 0:0b79cafcb387 68 };
bridadan 0:0b79cafcb387 69
bridadan 0:0b79cafcb387 70 #endif