hyperion.ng/libsrc/leddevice/dev_spi/LedDeviceWs2812SPI.cpp
2020-08-08 00:21:19 +02:00

100 lines
2.3 KiB
C++

#include "LedDeviceWs2812SPI.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
*/
LedDeviceWs2812SPI::LedDeviceWs2812SPI(const QJsonObject &deviceConfig)
: ProviderSpi(deviceConfig)
, SPI_BYTES_PER_COLOUR(4)
, SPI_FRAME_END_LATCH_BYTES(116)
, bitpair_to_byte {
0b10001000,
0b10001100,
0b11001000,
0b11001100,
}
{
}
LedDevice* LedDeviceWs2812SPI::construct(const QJsonObject &deviceConfig)
{
return new LedDeviceWs2812SPI(deviceConfig);
}
bool LedDeviceWs2812SPI::init(const QJsonObject &deviceConfig)
{
_baudRate_Hz = 2600000;
bool isInitOK = false;
// Initialise sub-class
if ( ProviderSpi::init(deviceConfig) )
{
WarningIf(( _baudRate_Hz < 2106000 || _baudRate_Hz > 3075000 ), _log, "SPI 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 LedDeviceWs2812SPI::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());
}