jamesabruce · August 5, 2014 17:04 · Aug 5, 2014
diff --git a/ambilight.ino b/ambilight.ino
@@ -0,0 +1,166 @@
+// Slightly modified Adalight protocol implementation that uses FastLED
+// library (http://fastled.io) for driving WS2811/WS2812 led stripe
+// Was tested only with Prismatik software from Lightpack project
+
+#include "FastLED.h"
+
+#define NUM_LEDS 114 // Max LED count
+#define LED_PIN 6 // arduino output pin
+#define GROUND_PIN 10
+#define BRIGHTNESS 255 // maximum brightness
+#define SPEED 115200 // virtual serial port speed, must be the same in boblight_config 
+
+CRGB leds[NUM_LEDS];
+uint8_t * ledsRaw = (uint8_t *)leds;
+
+// A 'magic word' (along with LED count & checksum) precedes each block
+// of LED data; this assists the microcontroller in syncing up with the
+// host-side software and properly issuing the latch (host I/O is
+// likely buffered, making usleep() unreliable for latch).  You may see
+// an initial glitchy frame or two until the two come into alignment.
+// The magic word can be whatever sequence you like, but each character
+// should be unique, and frequent pixel values like 0 and 255 are
+// avoided -- fewer false positives.  The host software will need to
+// generate a compatible header: immediately following the magic word
+// are three bytes: a 16-bit count of the number of LEDs (high byte
+// first) followed by a simple checksum value (high byte XOR low byte
+// XOR 0x55).  LED data follows, 3 bytes per LED, in order R, G, B,
+// where 0 = off and 255 = max brightness.
+
+static const uint8_t magic[] = {
+  'A','d','a'};
+#define MAGICSIZE  sizeof(magic)
+#define HEADERSIZE (MAGICSIZE + 3)
+
+#define MODE_HEADER 0
+#define MODE_DATA   2
+
+// If no serial data is received for a while, the LEDs are shut off
+// automatically.  This avoids the annoying "stuck pixel" look when
+// quitting LED display programs on the host computer.
+static const unsigned long serialTimeout = 150000; // 150 seconds
+
+void setup()
+{
+  pinMode(GROUND_PIN, OUTPUT); 
+  digitalWrite(GROUND_PIN, LOW);
+  FastLED.addLeds<WS2812B, LED_PIN, GRB>(leds, NUM_LEDS);
+
+  // Dirty trick: the circular buffer for serial data is 256 bytes,
+  // and the "in" and "out" indices are unsigned 8-bit types -- this
+  // much simplifies the cases where in/out need to "wrap around" the
+  // beginning/end of the buffer.  Otherwise there'd be a ton of bit-
+  // masking and/or conditional code every time one of these indices
+  // needs to change, slowing things down tremendously.
+  uint8_t
+    buffer[256],
+  indexIn       = 0,
+  indexOut      = 0,
+  mode          = MODE_HEADER,
+  hi, lo, chk, i, spiFlag;
+  int16_t
+    bytesBuffered = 0,
+  hold          = 0,
+  c;
+  int32_t
+    bytesRemaining;
+  unsigned long
+    startTime,
+  lastByteTime,
+  lastAckTime,
+  t;
+  int32_t outPos = 0;
+
+  Serial.begin(SPEED); // Teensy/32u4 disregards baud rate; is OK!
+
+  Serial.print("Ada\n"); // Send ACK string to host
+
+    startTime    = micros();
+  lastByteTime = lastAckTime = millis();
+
+  // loop() is avoided as even that small bit of function overhead
+  // has a measurable impact on this code's overall throughput.
+
+  for(;;) {
+
+    // Implementation is a simple finite-state machine.
+    // Regardless of mode, check for serial input each time:
+    t = millis();
+    if((bytesBuffered < 256) && ((c = Serial.read()) >= 0)) {
+      buffer[indexIn++] = c;
+      bytesBuffered++;
+      lastByteTime = lastAckTime = t; // Reset timeout counters
+    } 
+    else {
+      // No data received.  If this persists, send an ACK packet
+      // to host once every second to alert it to our presence.
+      if((t - lastAckTime) > 1000) {
+        Serial.print("Ada\n"); // Send ACK string to host
+        lastAckTime = t; // Reset counter
+      }
+      // If no data received for an extended time, turn off all LEDs.
+      if((t - lastByteTime) > serialTimeout) {
+        memset(leds, 0,  NUM_LEDS * sizeof(struct CRGB)); //filling Led array by zeroes
+        FastLED.show();
+        lastByteTime = t; // Reset counter
+      }
+    }
+
+    switch(mode) {
+
+    case MODE_HEADER:
+
+      // In header-seeking mode.  Is there enough data to check?
+      if(bytesBuffered >= HEADERSIZE) {
+        // Indeed.  Check for a 'magic word' match.
+        for(i=0; (i<MAGICSIZE) && (buffer[indexOut++] == magic[i++]););
+        if(i == MAGICSIZE) {
+          // Magic word matches.  Now how about the checksum?
+          hi  = buffer[indexOut++];
+          lo  = buffer[indexOut++];
+          chk = buffer[indexOut++];
+          if(chk == (hi ^ lo ^ 0x55)) {
+            // Checksum looks valid.  Get 16-bit LED count, add 1
+            // (# LEDs is always > 0) and multiply by 3 for R,G,B.
+            bytesRemaining = 3L * (256L * (long)hi + (long)lo + 1L);
+            bytesBuffered -= 3;
+            outPos = 0;
+            memset(leds, 0,  NUM_LEDS * sizeof(struct CRGB));
+            mode           = MODE_DATA; // Proceed to latch wait mode
+          } 
+          else {
+            // Checksum didn't match; search resumes after magic word.
+            indexOut  -= 3; // Rewind
+          }
+        } // else no header match.  Resume at first mismatched byte.
+        bytesBuffered -= i;
+      }
+      break;
+
+    case MODE_DATA:
+
+      if(bytesRemaining > 0) {
+        if(bytesBuffered > 0) {
+          if (outPos < sizeof(leds))
+            ledsRaw[outPos++] = buffer[indexOut++];   // Issue next byte
+          bytesBuffered--;
+          bytesRemaining--;
+        }
+        // If serial buffer is threatening to underrun, start
+        // introducing progressively longer pauses to allow more
+        // data to arrive (up to a point).
+      } 
+      else {
+        // End of data -- issue latch:
+        startTime  = micros();
+        mode       = MODE_HEADER; // Begin next header search
+        FastLED.show();
+      }
+    } // end switch
+  } // end for(;;)
+}
+
+void loop()
+{
+  // Not used.  See note in setup() function.
+}