Added support for sk6812RGBW leds (ab)using the SPI interface. (#61)

right now it only uses RGB - white is set to zero

libsrc/leddevice/LedDeviceSk6812SPI.cpp

@@ -0,0 +1,67 @@
+
+// STL includes
+#include <cstring>
+#include <cstdio>
+#include <iostream>
+
+// Linux includes
+#include <fcntl.h>
+#include <sys/ioctl.h>
+
+// hyperion local includes
+#include "LedDeviceSk6812SPI.h"
+
+LedDeviceSk6812SPI::LedDeviceSk6812SPI(const std::string& outputDevice, const unsigned baudrate) :
+	LedSpiDevice(outputDevice, baudrate, 0),
+	mLedCount(0),
+	bitpair_to_byte {
+		0b10001000,
+		0b10001100,
+		0b11001000,
+		0b11001100,
+	}
+
+{
+	// empty
+}
+
+int LedDeviceSk6812SPI::write(const std::vector<ColorRgb> &ledValues)
+{
+	mLedCount = ledValues.size();
+
+// 4 colours, 4 spi bytes per colour + 3 frame end latch bytes
+#define COLOURS_PER_LED		3
+#define SPI_BYTES_PER_COLOUR	4
+#define SPI_BYTES_PER_LED 	COLOURS_PER_LED * SPI_BYTES_PER_COLOUR
+
+	unsigned spi_size = mLedCount * SPI_BYTES_PER_LED + 3;
+	if(_spiBuffer.size() != spi_size){
+                _spiBuffer.resize(spi_size, 0x00);
+	}
+
+	unsigned spi_ptr = 0;
+        for (unsigned i=0; i< mLedCount; ++i) {
+		uint8_t white = 0;
+		uint32_t colorBits = 
+			((unsigned int)ledValues[i].red << 24) |
+			((unsigned int)ledValues[i].green << 16) |
+			((unsigned int)ledValues[i].blue << 8) |
+			white;
+
+		for (int j=SPI_BYTES_PER_LED - 1; j>=0; j--) {
+			_spiBuffer[spi_ptr+j] = bitpair_to_byte[ colorBits & 0x3 ];
+			colorBits >>= 2;
+		}
+		spi_ptr += SPI_BYTES_PER_LED;
+        }
+	_spiBuffer[spi_ptr++] = 0;
+	_spiBuffer[spi_ptr++] = 0;
+	_spiBuffer[spi_ptr++] = 0;
+
+	return writeBytes(spi_size, _spiBuffer.data());
+}
+
+int LedDeviceSk6812SPI::switchOff()
+{
+	return write(std::vector<ColorRgb>(mLedCount, ColorRgb{0,0,0}));
+}