Tachometer/Laser_Tachometer_V1_0_0.ino at master · EliteWorm/Tachometer · GitHub

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//Laser Tachometer by Elite Worm (YouTube.com/c/EliteWorm)
//Version 1.0.0

//Make sure you have all the libraries installed!

#include <SPI.h>
#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>

#define SCREEN_WIDTH 128
#define SCREEN_HEIGHT 32

#define OLED_RESET     4
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);

const byte sensor = 2;

volatile unsigned long t_pulse_started_volatile = 0;
volatile unsigned long t_pulse_duration_volatile = 0;
unsigned long t_pulse_started = 0;
unsigned long t_pulse_duration = 0;

long rpm_sum = 0;
long rpm_reading[100];
long rpm_average = 0;
byte n_max = 0;
byte n = 0;

volatile bool timeout = 1;
volatile bool newpulse = 0;

void setup() {

  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3C)) {
    for(;;);
  }

  pinMode(sensor, INPUT);
  attachInterrupt(digitalPinToInterrupt(sensor), ISR_sensor, RISING);

}

void loop() {

   noInterrupts();
   t_pulse_started = t_pulse_started_volatile;
   t_pulse_duration = t_pulse_duration_volatile;
   interrupts();

   if(((micros() - t_pulse_started) > 2000000) && timeout == 0 && newpulse == 0) {

     timeout = 1;
     rpm_average = 0;
     n = 0;

   };

   if(timeout == 0){

     if(newpulse){

       rpm_reading[n] = (60000000 / t_pulse_duration);
       n_max = constrain(map(rpm_reading[n], 60, 100000, 0, 100), 0, 100);
       n++;
       newpulse = 0;

       if(n > n_max){

         for (byte i = 0; i <= n_max; i++) {

           rpm_sum = rpm_sum + rpm_reading[i];

         };

         rpm_average = rpm_sum / (n_max + 1);
         rpm_sum = 0;
         n = 0;

       }

     }

   }

updatedisplay();

}

void updatedisplay() {

  byte x = 0;

  display.clearDisplay();
  display.setTextSize(3);

  if(rpm_average < 10) x = 80;
  if(rpm_average >= 10 && rpm_average < 100) x = 62;
  if(rpm_average >= 100 && rpm_average < 1000) x = 44;
  if(rpm_average >= 1000 && rpm_average < 10000) x = 26;
  if(rpm_average >= 10000 && rpm_average < 100000) x = 8;

  display.setTextColor(SSD1306_WHITE);

  if(rpm_average < 100000){

    display.setCursor(x, 6);
    display.print(rpm_average);
    display.setTextSize(1);
    display.setCursor(104, 20);
    display.print(F("RPM"));
    display.display();

  } else {

      display.setTextSize(2);
      display.setCursor(13, 8);
      display.print(F("MAX LIMIT"));
      display.display();

    }

}

void ISR_sensor() {

  t_pulse_duration_volatile = micros() - t_pulse_started_volatile;
  t_pulse_started_volatile = micros();
  timeout = 0;
  newpulse = 1;

}