Implement ftdi led device - 2 (#1746)

libsrc/leddevice/dev_ftdi/LedDeviceWs2812_ftdi.cpp

@@ -0,0 +1,93 @@
+#include "LedDeviceWs2812_ftdi.h"
+
+/*
+From the data sheet:
+
+(TH+TL=1.25μs±600ns)
+
+T0H,	 0 code, high level time,	 0.40µs ±0.150ns
+T0L,	 0 code, low level time,	 0.85µs ±0.150ns
+T1H,	 1 code, high level time,	 0.80µs ±0.150ns
+T1L,	 1 code, low level time,	 0.45µs ±0.150ns
+WT,	 Wait for the processing time,	 NA
+Trst,	 Reset code,low level time,	 50µs (not anymore... need 300uS for latest revision)
+
+To normalise the pulse times so they fit in 4 SPI bits:
+
+On the assumption that the "low" time doesnt matter much
+
+A SPI bit time of 0.40uS = 2.5 Mbit/sec
+T0 is sent as 1000
+T1 is sent as 1100
+
+With a bit of excel testing, we can work out the maximum and minimum speeds:
+2106000 MIN
+2590500 AVG
+3075000 MAX
+
+Wait time:
+Not Applicable for WS2812
+
+Reset time:
+using the max of 3075000, the bit time is 0.325
+Reset time is 300uS = 923 bits = 116 bytes
+
+*/
+
+LedDeviceWs2812_ftdi::LedDeviceWs2812_ftdi(const QJsonObject &deviceConfig)
+	: ProviderFtdi(deviceConfig),
+	  SPI_BYTES_PER_COLOUR(4),
+	  SPI_FRAME_END_LATCH_BYTES(116),
+	  bitpair_to_byte{
+		  0b10001000,
+		  0b10001100,
+		  0b11001000,
+		  0b11001100,
+	  }
+{
+}
+
+LedDevice *LedDeviceWs2812_ftdi::construct(const QJsonObject &deviceConfig)
+{
+	return new LedDeviceWs2812_ftdi(deviceConfig);
+}
+
+bool LedDeviceWs2812_ftdi::init(const QJsonObject &deviceConfig)
+{
+	bool isInitOK = false;
+
+	// Initialise sub-class
+	if (ProviderFtdi::init(deviceConfig))
+	{
+		WarningIf((_baudRate_Hz < 2106000 || _baudRate_Hz > 3075000), _log, "Baud rate %d outside recommended range (2106000 -> 3075000)", _baudRate_Hz);
+		_ledBuffer.resize(_ledRGBCount * SPI_BYTES_PER_COLOUR + SPI_FRAME_END_LATCH_BYTES, 0x00);
+		isInitOK = true;
+	}
+
+	return isInitOK;
+}
+
+int LedDeviceWs2812_ftdi::write(const std::vector<ColorRgb> &ledValues)
+{
+	unsigned spi_ptr = 0;
+	const int SPI_BYTES_PER_LED = sizeof(ColorRgb) * SPI_BYTES_PER_COLOUR;
+
+	for (const ColorRgb &color : ledValues)
+	{
+		uint32_t colorBits = ((unsigned int)color.red << 16) | ((unsigned int)color.green << 8) | color.blue;
+
+		for (int j = SPI_BYTES_PER_LED - 1; j >= 0; j--)
+		{
+			_ledBuffer[spi_ptr + j] = bitpair_to_byte[colorBits & 0x3];
+			colorBits >>= 2;
+		}
+		spi_ptr += SPI_BYTES_PER_LED;
+	}
+
+	for (int j = 0; j < SPI_FRAME_END_LATCH_BYTES; j++)
+	{
+		_ledBuffer[spi_ptr++] = 0;
+	}
+
+	return writeBytes(_ledBuffer.size(), _ledBuffer.data());
+}