Add EyeLights googly rings Arduino code

EyeLights_Googly_Rings/EyeLights_Googly_Rings.ino

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+/*
+GOOGLY EYES for Adafruit EyeLight LED glasses + driver. Pendulum physics
+simulation using accelerometer and math. This uses only the rings, not the
+matrix portion. Adapted from Bill Earl's STEAM-Punk Goggles project:
+https://learn.adafruit.com/steam-punk-goggles
+*/
+
+#include <Adafruit_IS31FL3741.h> // For LED driver
+#include <Adafruit_LIS3DH.h>     // For accelerometer
+#include <Adafruit_Sensor.h>     // For m/s^2 accel units
+
+Adafruit_LIS3DH             accel;
+Adafruit_EyeLights_buffered glasses; // Buffered for smooth animation
+
+// A small class for our pendulum simulation.
+class Pendulum {
+public:
+  // Constructor. Pass pointer to EyeLights ring, and a 3-byte color array.
+  Pendulum(Adafruit_EyeLights_Ring_buffered *r, uint8_t *c) {
+    ring  = r;
+    color = c;
+    // Initial pendulum position, plus axle friction, are randomized
+    // so rings don't spin in perfect lockstep.
+    angle = random(1000);
+    momentum = 0.0;
+    friction = 0.9 + random(500) * 0.0001; // Inverse friction, really
+  }
+
+  // Given a pixel index (0-23) and a scaling factor (0.0-1.0),
+  // interpolate between LED "off" color (at 0.0) and this item's fully-
+  // lit color (at 1.0) and set pixel to the result.
+  void interp(uint8_t pixel, float scale) {
+    // Convert separate red, green, blue to "packed" 24-bit RGB value
+    ring->setPixelColor(pixel,
+        (int(color[0] * scale) << 16) |
+        (int(color[1] * scale) <<  8) |
+         int(color[2] * scale));
+  }
+
+  // Given an accelerometer reading, run one cycle of the pendulum
+  // physics simulation and render the corresponding LED ring.
+  void iterate(sensors_event_t &event) {
+    // Minus here is because LED pixel indices run clockwise vs. trigwise.
+    // 0.004 is just an empirically-derived scaling fudge factor that looks
+    // good; smaller values for more sluggish rings, higher = more twitch.
+    momentum =  momentum * friction - 0.004 *
+      (cos(angle) * event.acceleration.z +
+       sin(angle) * event.acceleration.x);
+    angle += momentum;
+
+    // Scale pendulum angle into pixel space
+    float midpoint = fmodf(angle * 12.0 / M_PI, 24.0);
+
+    // Go around the whole ring, setting each pixel based on proximity
+    // (this is also to erase the prior position)...
+    for (uint8_t i=0; i<24; i++) {
+        float dist = fabs(midpoint - (float)i); // Pixel to pendulum distance...
+        if (dist > 12.0)                   // If it crosses the "seam" at top,
+            dist = 24.0 - dist;            //   take the shorter path.
+        if (dist > 5.0)                    // Not close to pendulum,
+            ring->setPixelColor(i, 0);     //   erase pixel.
+        else if (dist < 2.0)               // Close to pendulum,
+            interp(i, 1.0);                //   solid color
+        else                               // Anything in-between,
+            interp(i, (5.0 - dist) / 3.0); //   interpolate
+    }
+  }
+private:
+  Adafruit_EyeLights_Ring_buffered *ring; // -> glasses ring
+  uint8_t *color;    // -> array of 3 uint8_t's [R,G,B]
+  float    angle;    // Current position around ring
+  float    momentum; // Current 'oomph'
+  float    friction; // A scaling constant to dampen motion
+};
+
+Pendulum pendulums[] = {
+    Pendulum(&glasses.left_ring, (uint8_t[3]){0, 20, 50}),  // Cerulean blue,
+    Pendulum(&glasses.right_ring, (uint8_t[3]){0, 20, 50}), // 50 is plenty bright!
+};
+#define N_PENDULUMS (sizeof pendulums / sizeof pendulums[0])
+
+// Crude error handler, prints message to Serial console, flashes LED
+void err(char *str, uint8_t hz) {
+  Serial.println(str);
+  pinMode(LED_BUILTIN, OUTPUT);
+  for (;;) digitalWrite(LED_BUILTIN, (millis() * hz / 500) & 1);
+}
+
+void setup() { // Runs once at program start...
+
+  // Initialize hardware
+  Serial.begin(115200);
+  if (! accel.begin())   err("LIS3DH not found", 5);
+  if (! glasses.begin()) err("IS3741 not found", 2);
+
+  // Configure glasses for max brightness, enable output
+  glasses.setLEDscaling(0xFF);
+  glasses.setGlobalCurrent(0xFF);
+  glasses.enable(true);
+}
+
+void loop() { // Repeat forever...
+  sensors_event_t event;
+  accel.getEvent(&event); // Read accelerometer once
+  for (uint8_t i=0; i<N_PENDULUMS; i++) { // For each pendulum...
+    pendulums[i].iterate(event);          // Do math with accel data
+  }
+  glasses.show();
+}