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package com.diozero.ws281xj.spi;
/*-
* #%L
* Organisation: diozero
* Project: diozero - WS281x Java Wrapper
* Filename: WS281xSpi.java
*
* This file is part of the diozero project. More information about this project
* can be found at https://www.diozero.com/.
* %%
* Copyright (C) 2016 - 2021 diozero
* %%
* 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.
* #L%
*/
import java.util.Arrays;
import org.tinylog.Logger;
import com.diozero.api.SpiDevice;
import com.diozero.util.SleepUtil;
import com.diozero.ws281xj.LedDriverInterface;
import com.diozero.ws281xj.StripType;
/**
* References:
* https://os.mbed.com/users/JacobBramley/code/PixelArray/file/47802e75974e/neopixel.cpp
* https://github.com/jgarff/rpi_ws281x/blob/master/ws2811.c
*/
public class WS281xSpi implements LedDriverInterface {
private static final int LED_COLOURS = 4;
private static final int LED_RESET_uS = 55;
/* Minimum time to wait for reset to occur in nanoseconds. */
private static final int LED_RESET_WAIT_TIME = 300_000;
// Symbol definitions
private static final byte SYMBOL_HIGH = 0b110;
private static final byte SYMBOL_LOW = 0b100;
// Symbol definitions for software inversion (PCM and SPI only)
private static final byte SYMBOL_HIGH_INV = 0b001;
private static final byte SYMBOL_LOW_INV = 0b011;
/*
* 4 colours (R, G, B + W), 8 bits per byte, 3 symbols per bit + 55uS low for
* reset signal
*/
private SpiDevice device;
private Protocol protocol;
private StripType stripType;
private int numLeds;
private long lastRenderTime;
private int renderWaitTime;
// Brightness value between 0 and 255
private int brightness;
private int[] leds;
private byte[] gamma;
private byte[] pixelRaw;
public WS281xSpi(int controller, int chipSelect, StripType stripType, int numLeds, int brightness) {
this(controller, chipSelect, Protocol.PROTOCOL_800KHZ, stripType, numLeds, brightness);
}
public WS281xSpi(int controller, int chipSelect, Protocol protocol, StripType stripType, int numLeds,
int brightness) {
device = SpiDevice.builder(chipSelect).setController(controller).setFrequency(protocol.getFrequency() * 3)
.build();
this.protocol = protocol;
this.stripType = stripType;
this.numLeds = numLeds;
this.brightness = brightness & 0xff;
leds = new int[numLeds];
gamma = new byte[256];
// Set default uncorrected gamma table
for (int x = 0; x < 256; x++) {
gamma[x] = (byte) x;
}
// Allocate SPI transmit buffer (same size as PCM)
pixelRaw = new byte[PCM_BYTE_COUNT(numLeds, protocol.getFrequency())];
// 1.25us per bit (1250ns)
renderWaitTime = numLeds * stripType.getColourCount() * 8 * 1250 + LED_RESET_WAIT_TIME;
}
@Override
public void close() {
Logger.trace("Turning all off before close");
allOff();
device.close();
}
@Override
public int getNumPixels() {
return numLeds;
}
@Override
public int getPixelColour(int pixel) {
return leds[pixel];
}
@Override
public void setPixelColour(int pixel, int colour) {
leds[pixel] = colour;
}
/**
* Pixels are sent as follows: - The first transmitted pixel is the pixel
* closest to the transmitter. - The most significant bit is always sent first.
*
* g7,g6,g5,g4,g3,g2,g1,g0,r7,r6,r5,r4,r3,r2,r1,r0,b7,b6,b5,b4,b3,b2,b1,b0
* \_____________________________________________________________________/ |
* _________________... | / __________________... | / / ___________________... |
* / / / GRB,GRB,GRB,GRB,...
*
* For BYTE_ORDER_RGB, the order of the first two bytes are reversed.
*/
@Override
public void render() {
int bitpos = 7;
int bytepos = 0;
int scale = brightness + 1;
// int array_size = stripType.getWhiteShift() == 0 ? 3 : 4; // RGB or RGBW
int colour_count = stripType.getColourCount();
for (int i = 0; i < numLeds; i++) {
// Swap the colours around based on the led strip type
byte[] colour = { gamma[(((leds[i] >> stripType.getRedShift()) & 0xff) * scale) >> 8],
gamma[(((leds[i] >> stripType.getGreenShift()) & 0xff) * scale) >> 8],
gamma[(((leds[i] >> stripType.getBlueShift()) & 0xff) * scale) >> 8],
gamma[(((leds[i] >> stripType.getWhiteShift()) & 0xff) * scale) >> 8] };
// Colour
for (int j = 0; j < colour_count; j++) {
// Bit
for (int k = 7; k >= 0; k--) {
int symbol = ((colour[j] & (1 << k)) != 0) ? SYMBOL_HIGH : SYMBOL_LOW;
// Symbol
for (int l = 2; l >= 0; l--) {
/*
* volatile byte *byteptr = &pxl_raw[bytepos]; byteptr &= ~(1 << bitpos); if
* (symbol & (1 << l)) { byteptr |= (1 << bitpos); }
*/
pixelRaw[bytepos] &= ~(1 << bitpos);
if ((symbol & (1 << l)) != 0) {
pixelRaw[bytepos] |= (1 << bitpos);
}
bitpos--;
if (bitpos < 0) {
bytepos++;
bitpos = 7;
}
}
}
}
}
if (lastRenderTime != 0) {
int diff = (int) (System.nanoTime() - lastRenderTime);
if (renderWaitTime > diff) {
SleepUtil.busySleep(renderWaitTime - diff);
}
}
device.write(pixelRaw);
lastRenderTime = System.nanoTime();
}
@Override
public void allOff() {
Arrays.fill(leds, 0);
render();
}
private static final int LED_BIT_COUNT(int numLeds, int frequency) {
return (numLeds * LED_COLOURS * 8 * 3) + ((LED_RESET_uS * (frequency * 3)) / 1000000);
}
private static final int PCM_BYTE_COUNT(int numLeds, int frequency) {
return (((LED_BIT_COUNT(numLeds, frequency) >> 3) & ~0x7) + 4) + 4;
}
public enum Protocol {
/**
*
* 800kHz bit encodings: '0': ----________ '1': --------____ The period is
* 1.25us, giving a basic frequency of 800kHz. Getting the mark-space ratio
* right is trickier, though. There are a number of different timings, and the
* correct (documented) values depend on the controller chip.
*
* The _real_ timing restrictions are much simpler though, and someone has
* published a lovely analysis here:
* http://cpldcpu.wordpress.com/2014/01/14/light_ws2812-library-v2-0-part-i-understanding-the-ws2812/
*
* In summary: - The period should be at least 1.25us. - The '0' high time can
* be anywhere from 0.0625us to 0.5us. - The '1' high time should be longer than
* 0.625us.
*
* These constraints are easy to meet by splitting each bit into three and
* packing them into SPI packets. '0': 100 mark: 0.42us, space: 0.83us '1': 110
* mark: 0.83us, space: 0.42us
*/
PROTOCOL_800KHZ(800_000),
/**
* 400kHz bit encodings: '0': --________ '1': -----_____
*
* Timing requirements are derived from this document:
* http://www.adafruit.com/datasheets/WS2811.pdf
*
* The period is 2.5us, and we use a 10-bit packet for this encoding: '0':
* 1100000000 mark: 0.5us, space: 2us '1': 1111100000 mark: 1.25us, space:
* 1.25us
*/
PROTOCOL_400KHZ(400_000);
int frequency;
Protocol(int frequency) {
this.frequency = frequency;
}
public int getFrequency() {
return frequency;
}
}
}
