TeensyCountdown.cpp

/* Analog Control RGB LED Color, Teensyduino Tutorial #4
   http://www.pjrc.com/teensy/tutorial4.html

   This example code is in the public domain.
*/

// TODO: Save to GitHub gist
const int outPin =  12;

void setup() {
  pinMode(outPin, OUTPUT);
  analogWriteResolution(14);
  delay(1000); // Delay in ms to set up the camera.
}

// 3.299 V when in standby mode
// 3.297 V when running a program
float calibrated_3_3V = 3.294;
int16_t counter = 32;

// 28 Hz lowpass on 9.2 kHz PWM output
// - 5.56 μF -> 5.60 μF after 10 s dielectric absorption
//   (sort of like piezoelectric creep for electrolytics)
//   5.67 μF -> 5.62 μF (changes with configuration)
// - 1 kΩ
// - Engineered in an attempt to stabilize the
//   multimeter's DC voltage reading.

void loop()
{
  float desiredVoltage = float(counter) / 10;
  float normalizedValue = desiredVoltage / calibrated_3_3V;
  int16_t quantized_10unorm = int16_t(normalizedValue * 16384);
  analogWrite(outPin, quantized_10unorm);

  if (counter > 0) {
    counter -= 1;
  }

  // Delay in ms before next loop iteration.
  delay(1000);
}