arduino-tachometer

led-tach.ino

#include <Adafruit_NeoPixel.h>

const int LED_PIN = 6;
const int TACH_PIN = 2;
const int BRIGHTNESS = 100;
const int LED_COUNT = 80;
const int REDLINE = 7500;
const int WARN_RPM = 6000;
const int WARN_INTERVAL = 70;

// Parameter 1 = number of pixels in strip
// Parameter 2 = Arduino LED_PIN number (most are valid)
// Parameter 3 = pixel type flags, add together as needed:
//   NEO_KHZ800  800 KHz bitstream (most NeoPixel products w/WS2812 LEDs)
//   NEO_KHZ400  400 KHz (classic 'v1' (not v2) FLORA pixels, WS2811 drivers)
//   NEO_GRB     Pixels are wired for GRB bitstream (most NeoPixel products)
//   NEO_RGB     Pixels are wired for RGB bitstream (v1 FLORA pixels, not v2)
//   NEO_RGBW    Pixels are wired for RGBW bitstream (NeoPixel RGBW products)
Adafruit_NeoPixel strip = Adafruit_NeoPixel(LED_COUNT, LED_PIN, NEO_GRB + NEO_KHZ800);

// IMPORTANT: To reduce NeoPixel burnout risk, add 1000 uF capacitor across
// pixel power leads, add 300 - 500 Ohm resistor on first pixel's data input
// and minimize distance between Arduino and first pixel.  Avoid connecting
// on a live circuit...if you must, connect GND first.

bool blinkState = true;
unsigned long lastBlinkUpdate = 0;

volatile unsigned long lastIgnitionTime = 0;

void recordIgnition() {
  detachInterrupt(digitalPinToInterrupt(TACH_PIN));

  lastIgnitionTime = millis();
  
  attachInterrupt(digitalPinToInterrupt(TACH_PIN), calculateRpm, RISING);
}

void calculateRpm() {
  detachInterrupt(digitalPinToInterrupt(TACH_PIN));

  unsigned long ignitionTimeDelta = millis() - lastIgnitionTime;

  int rpm = 1000.0 / ignitionTimeDelta * 60 *2;

  Serial.print("RPM: ");
  Serial.println(rpm);

  setRpm(rpm);

  attachInterrupt(digitalPinToInterrupt(TACH_PIN), recordIgnition, RISING);
}

void setup() {
  // Open serial communications and wait for port to open:
  Serial.begin(9600);

  pinMode(TACH_PIN, INPUT);
  
  strip.begin();
  strip.setBrightness(BRIGHTNESS);
  strip.show(); // Initialize all pixels to 'off'

  attachInterrupt(digitalPinToInterrupt(TACH_PIN), recordIgnition, RISING);
}

void loop() {
}

void setRpm(int rpm) {

  int rpmPerLed = REDLINE / LED_COUNT;

  //blink for warn function
  if(rpm >= WARN_RPM) {
    unsigned long currentTime = millis();

    if(currentTime - lastBlinkUpdate > WARN_INTERVAL) {
      lastBlinkUpdate = currentTime;
      blinkState = !blinkState;
    }
  }
  else
    blinkState = true;

  for(int led = 0; led < LED_COUNT; led++) {

    if(!blinkState && (led+2)*rpmPerLed > WARN_RPM) {
      strip.setPixelColor(led, 0, 0, 0);
      continue;
    }
      
    
    if((led+1)*rpmPerLed <= rpm)
      strip.setPixelColor(led, getColor((led+1)*rpmPerLed, 1));
    else if(led*rpmPerLed < rpm && (led+1)*rpmPerLed > rpm) {
      strip.setPixelColor(led, getColor(rpm, (double)(rpm-(led)*rpmPerLed)/rpmPerLed)); 
    }
    else
      strip.setPixelColor(led, 0, 0, 0);
  }

  strip.show();
}

uint32_t getColor(int rpm, double intensity) {
  int red = rpm/(double)REDLINE * 255 * intensity;
  int green = (1-rpm/(double)REDLINE) * 255 * intensity;
  int blue = 0;

  return strip.Color(red, green, blue);
}