#25 Allow channel to be specified in ws281x library

diozero-ws281x-java/src/main/java/com/diozero/ws281xj/WS281x.java

@@ -46,13 +46,19 @@
  * <a href="https://github.com/jgarff/rpi_ws281x">rpi_ws281x C library</a>.</p>
  * <p>Also see <a href="https://github.com/626Pilot/RaspberryPi-NeoPixel-WS2812">this implementation</a>.</p>
  * <p>All colours are represented as 24bit RGB values.</p>
+ * <p>Valid GPIO numbers:</p>
+ * <ul>
+ *  <li>12 / 18 (PWM)</li>
+ *  <li>21 / 31 (PCM)</li>
+ *  <li>10 (SPI)</li>
+ * </ul>
  */
 public class WS281x implements Closeable {
 	private static final int SIZE_OF_INT = 4;
 	private static final int DEFAULT_FREQUENCY = 800_000; // Or 400_000
-	// TODO Find out what options there are here... What do pigpio & wiringPi
-	// use?
+	// TODO Find out what options there are here... What do pigpio & wiringPi use?
 	private static final int DEFAULT_DMA_NUM = 5;
+	private static final int DEFAULT_CHANNEL = 0;
 
 	private static final String LIB_NAME = "ws281xj";
 	private static Boolean loaded = Boolean.FALSE;
@@ -90,7 +96,7 @@ private static void init() {
 	 * @param numPixels The number of pixels connected.
 	 */
 	public WS281x(int gpioNum, int brightness, int numPixels) {
-		this(DEFAULT_FREQUENCY, DEFAULT_DMA_NUM, gpioNum, brightness, numPixels, StripType.WS2812_STRIP);
+		this(DEFAULT_FREQUENCY, DEFAULT_DMA_NUM, gpioNum, brightness, numPixels, StripType.WS2812_STRIP, DEFAULT_CHANNEL);
 	}
 
 	/**
@@ -102,11 +108,24 @@ public WS281x(int gpioNum, int brightness, int numPixels) {
 	 * @param stripType Strip type
 	 */
 	public WS281x(int frequency, int dmaNum, int gpioNum, int brightness, int numPixels, StripType stripType) {
+		this(DEFAULT_FREQUENCY, DEFAULT_DMA_NUM, gpioNum, brightness, numPixels, stripType, DEFAULT_CHANNEL);
+	}
+
+	/**
+	 * @param frequency Communication frequency, 800,000 or 400,000.
+	 * @param dmaNum DMA number.
+	 * @param gpioNum GPIO pin to use to drive the LEDs.
+	 * @param brightness Brightness level (0..255).
+	 * @param numPixels The number of pixels connected.
+	 * @param stripType Strip type
+	 * @param channel PWM channel
+	 */
+	public WS281x(int frequency, int dmaNum, int gpioNum, int brightness, int numPixels, StripType stripType, int channel) {
 		init();
 
 		this.numPixels = numPixels;
 
-		ch0LedBuffer = WS281xNative.initialise(frequency, dmaNum, gpioNum, brightness, numPixels, stripType.getType());
+		ch0LedBuffer = WS281xNative.initialise(frequency, dmaNum, gpioNum, brightness, numPixels, stripType.getType(), channel);
 		if (ch0LedBuffer == null) {
 			throw new RuntimeException("Error initialising the WS281x strip");
 		}

diozero-ws281x-java/src/main/java/com/diozero/ws281xj/WS281xNative.java

@@ -35,7 +35,7 @@
 import java.nio.ByteBuffer;
 
 public class WS281xNative {
-	public static native ByteBuffer initialise(int frequency, int dmaNum, int gpioNum, int brightness, int numPixels, int stripType);
+	public static native ByteBuffer initialise(int frequency, int dmaNum, int gpioNum, int brightness, int numPixels, int stripType, int channel);
 	public static native void terminate();
 	public static native int render();
 }

diozero-ws281x-native/src/main/native/com_diozero_ws281xj_WS281x.c

@@ -11,20 +11,17 @@
 #include "com_diozero_ws281xj_WS281x.h"
 
 #define TARGET_FREQ WS2811_TARGET_FREQ
-#define GPIO_PIN 18
 #define DMA 5
-#define LED_COUNT 60
 
 ws2811_t led_string = {
-	.freq = TARGET_FREQ,
-	.dmanum = DMA,
+	.freq = 0,
+	.dmanum = 0,
 	.channel = {
 		[0] = {
-			.gpionum = GPIO_PIN,
-			.count = LED_COUNT,
+			.gpionum = 0,
+			.count = 0,
 			.invert = 0,
-			.brightness = 63,
-			.strip_type = WS2812_STRIP
+			.brightness = 0
 		}, [1] = {
 			.gpionum = 0,
 			.count = 0,
@@ -42,16 +39,22 @@ JNIEXPORT jint JNICALL JNI_OnLoad(JavaVM* jvm, void* reserved) {
 /*
  * Class:     com_diozero_ws281xj_WS281xNative
  * Method:    initialise
- * Signature: (IIIIII)Ljava/nio/ByteBuffer
+ * Signature: (IIIIIII)Ljava/nio/ByteBuffer
  */
 JNIEXPORT jobject JNICALL Java_com_diozero_ws281xj_WS281xNative_initialise(
-		JNIEnv* env, jclass clz, jint frequency, jint dmaNum, jint gpioNum, jint brightness, jint numLeds, jint stripType) {
+		JNIEnv* env, jclass clz, jint frequency, jint dmaNum, jint gpioNum,
+		jint brightness, jint numLeds, jint stripType, jint channel) {
+	if (channel < 0 || channel >= RPI_PWM_CHANNELS) {
+		fprintf(stderr, "Error channel must be 0..%d\n", RPI_PWM_CHANNELS - 1);
+		return NULL;
+	}
+
 	led_string.freq = frequency;
 	led_string.dmanum = dmaNum;
-	led_string.channel[0].gpionum = gpioNum;
-	led_string.channel[0].count = numLeds;
-	led_string.channel[0].brightness = brightness;
-	led_string.channel[0].strip_type = stripType;
+	led_string.channel[channel].gpionum = gpioNum;
+	led_string.channel[channel].count = numLeds;
+	led_string.channel[channel].brightness = brightness;
+	led_string.channel[channel].strip_type = stripType;
 	int rc = ws2811_init(&led_string);
 	if (rc != 0) {
 		fprintf(stderr, "ws2811_init failed: %s\n", ws2811_get_return_t_str(rc));