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100 lines
2.3 KiB
C++
100 lines
2.3 KiB
C++
#include "LedDeviceWs2812SPI.h"
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/*
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From the data sheet:
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(TH+TL=1.25μs±600ns)
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T0H, 0 code, high level time, 0.40µs ±0.150ns
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T0L, 0 code, low level time, 0.85µs ±0.150ns
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T1H, 1 code, high level time, 0.80µs ±0.150ns
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T1L, 1 code, low level time, 0.45µs ±0.150ns
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WT, Wait for the processing time, NA
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Trst, Reset code,low level time, 50µs (not anymore... need 300uS for latest revision)
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To normalise the pulse times so they fit in 4 SPI bits:
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On the assumption that the "low" time doesnt matter much
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A SPI bit time of 0.40uS = 2.5 Mbit/sec
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T0 is sent as 1000
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T1 is sent as 1100
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With a bit of excel testing, we can work out the maximum and minimum speeds:
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2106000 MIN
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2590500 AVG
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3075000 MAX
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Wait time:
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Not Applicable for WS2812
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Reset time:
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using the max of 3075000, the bit time is 0.325
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Reset time is 300uS = 923 bits = 116 bytes
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*/
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LedDeviceWs2812SPI::LedDeviceWs2812SPI(const QJsonObject &deviceConfig)
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: ProviderSpi(deviceConfig)
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, SPI_BYTES_PER_COLOUR(4)
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, SPI_FRAME_END_LATCH_BYTES(116)
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, bitpair_to_byte {
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0b10001000,
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0b10001100,
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0b11001000,
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0b11001100,
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}
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{
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}
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LedDevice* LedDeviceWs2812SPI::construct(const QJsonObject &deviceConfig)
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{
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return new LedDeviceWs2812SPI(deviceConfig);
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}
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bool LedDeviceWs2812SPI::init(const QJsonObject &deviceConfig)
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{
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_baudRate_Hz = 2600000;
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bool isInitOK = false;
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// Initialise sub-class
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if ( ProviderSpi::init(deviceConfig) )
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{
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WarningIf(( _baudRate_Hz < 2106000 || _baudRate_Hz > 3075000 ), _log, "SPI rate %d outside recommended range (2106000 -> 3075000)", _baudRate_Hz);
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_ledBuffer.resize(_ledRGBCount * SPI_BYTES_PER_COLOUR + SPI_FRAME_END_LATCH_BYTES, 0x00);
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isInitOK = true;
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}
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return isInitOK;
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}
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int LedDeviceWs2812SPI::write(const std::vector<ColorRgb> &ledValues)
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{
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unsigned spi_ptr = 0;
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const int SPI_BYTES_PER_LED = sizeof(ColorRgb) * SPI_BYTES_PER_COLOUR;
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for (const ColorRgb& color : ledValues)
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{
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uint32_t colorBits = ((unsigned int)color.red << 16)
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| ((unsigned int)color.green << 8)
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| color.blue;
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for (int j=SPI_BYTES_PER_LED - 1; j>=0; j--)
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{
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_ledBuffer[spi_ptr+j] = bitpair_to_byte[ colorBits & 0x3 ];
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colorBits >>= 2;
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}
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spi_ptr += SPI_BYTES_PER_LED;
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}
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for (int j=0; j < SPI_FRAME_END_LATCH_BYTES; j++)
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{
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_ledBuffer[spi_ptr++] = 0;
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}
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return writeBytes(_ledBuffer.size(), _ledBuffer.data());
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}
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