November 23, 2016 21:29 · Nov 23, 2016
diff --git a/pixel-wave.ino b/pixel-wave.ino
@@ -0,0 +1,72 @@
+/* Pixel wave
+ * Copyright 2016 Julien Vanier, MIT license
+ *
+ * Connect 3 photoresistors to analog inputs and drive a Dotstar/Neopixel strip from the 3 analog signals!
+ */
+#include "application.h"
+#include "dotstar/dotstar.h"
+
+SYSTEM_THREAD(ENABLED);
+
+// IMPORTANT: Connect Dotstar strand to hardware SPI (Data => A5 and Clock => A3)
+#define PIXEL_COUNT 72
+#define BRIGHTNESS 255
+#define SPEED 10
+
+#define PIN_RED A0
+#define PIN_GREEN A1
+#define PIN_BLUE A6
+
+#define VOLTAGE_MAX_NOMINAL (3.3 * 256 / 4096)
+#define VOLTAGE_MAX_RED 0.190
+#define VOLTAGE_MAX_GREEN 0.220
+#define VOLTAGE_MAX_BLUE 0.130
+
+Adafruit_DotStar strip = Adafruit_DotStar(PIXEL_COUNT, DOTSTAR_BGR);
+
+uint32_t colors[PIXEL_COUNT] = { 0 };
+
+uint16_t pos = 0;
+
+void setup()
+{
+  strip.begin();
+  strip.setBrightness(BRIGHTNESS);
+  strip.show();
+
+  pinMode(PIN_RED, INPUT);
+  pinMode(PIN_GREEN, INPUT);
+  pinMode(PIN_BLUE, INPUT);
+}
+
+void loop() {
+    updateColor();
+    showStrip();
+    delay(SPEED);
+}
+
+void updateColor() {
+    colors[pos] = strip.Color(
+        pinColor(PIN_RED, VOLTAGE_MAX_RED),
+        pinColor(PIN_GREEN, VOLTAGE_MAX_GREEN),
+        pinColor(PIN_BLUE, VOLTAGE_MAX_BLUE)
+        );
+}
+
+uint8_t pinColor(pin_t pin, float voltageMax) {
+    int value = (int)(analogRead(pin) * VOLTAGE_MAX_NOMINAL / voltageMax);
+    if (value > 255) {
+        value = 255;
+    }
+
+    return 255 - value;
+}
+
+void showStrip() {
+    for (uint16_t i = 0; i < PIXEL_COUNT; i++) {
+        uint16_t n = (i + pos) % PIXEL_COUNT;
+        strip.setPixelColor(PIXEL_COUNT - i, colors[n]);
+    }
+    strip.show();
+    pos = (pos + 1) % PIXEL_COUNT;
+}