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/

Diff: WS2812.h

Revision:
0:0b79cafcb387
Child:
1:aadbf08c62a2
--- /dev/null	Thu Jan 01 00:00:00 1970 +0000
+++ b/WS2812.h	Thu Feb 12 19:17:10 2015 +0000
@@ -0,0 +1,70 @@
+/* Copyright (c) 2012 cstyles, MIT License
+ *
+ * Permission is hereby granted, free of charge, to any person obtaining a copy of this software
+ * and associated documentation files (the "Software"), to deal in the Software without restriction,
+ * including without limitation the rights to use, copy, modify, merge, publish, distribute,
+ * sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is
+ * furnished to do so, subject to the following conditions:
+ *
+ * The above copyright notice and this permission notice shall be included in all copies or
+ * substantial portions of the Software.
+ *
+ * THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING
+ * BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND
+ * NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM,
+ * DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+ * OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.
+ */
+
+#ifndef WS2812_H
+#define WS2812_H
+
+#include "mbed.h"
+
+#define WS1 0x38
+#define WS0 0x30
+#define SPICLK 5000000
+#define FRAME_SIZE 24
+
+
+//!Library for the WS2812 RGB LED with integrated controller
+/*!
+The WS2812 is controller that is built into a range of LEDs
+*/
+class WS2812
+{
+public:
+    //!Creates an instance of the class.
+    /*!
+    Connect WS2812 address addr using digital pins
+    */
+    WS2812(PinName d, int size);
+
+    /*!
+    Destroys instance.
+    */
+    ~WS2812();
+    
+    void setDelays(int zeroHigh, int zeroLow, int oneHigh, int oneLow);
+
+    void write(int buf[]);
+    void write_offsets(int buf[],int r_offset=0, int g_offset=0, int b_offset=0);
+
+    void useII(int d);
+    void setII(unsigned char II);
+    
+
+
+private:
+
+    int __size;
+    int __zeroHigh, __zeroLow, __oneHigh, __oneLow;
+    unsigned char __II;
+    int __use_II;
+    bool *__transmitBuf;
+    void __loadBuf(int buf[],int r_offset=0, int g_offset=0, int b_offset=0);
+    PinName __outPin;
+    DigitalOut __gpo;
+};
+
+#endif
\ No newline at end of file