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

#define SCREEN_WIDTH 128 // OLED display width, in pixels
#define SCREEN_HEIGHT 64 // OLED display height, in pixels

// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
#define OLED_RESET     4 // Reset pin # (or -1 if sharing Arduino reset pin)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, OLED_RESET);
const int sensorPin = 3;   // Digital pin connected to the sensor
volatile int counter = 0;  // Counter for the number of pulses
unsigned long startTime;   // Start time of each measurement


void setup() {
  pinMode(sensorPin, INPUT_PULLUP);
  attachInterrupt(digitalPinToInterrupt(sensorPin), countPulse, FALLING);
  Serial.begin(9600);

  // SSD1306_SWITCHCAPVCC = generate display voltage from 3.3V internally
  if(!display.begin(SSD1306_SWITCHCAPVCC, 0x3D)) { // Address 0x3D for 128x64
    Serial.println(F("SSD1306 allocation failed"));
    for(;;); // Don't proceed, loop forever
  }
  display.display();
  delay(2000); // Pause for 2 seconds
  display.clearDisplay();

}

void loop() {
// Reset the counter and start time for each measurement
  counter = 0;
  startTime = millis();

  // Wait for one second to count pulses
  delay(1000);

  // Calculate RPM
  unsigned long endTime = millis();
  unsigned long elapsedTime = endTime - startTime;
  float rpm = (float)counter / (float)elapsedTime * 60000.0;  // RPM = (Pulses / Time) * 60000 (60 seconds * 1000 milliseconds)

  // Display RPM in the serial monitor
  Serial.print("RPM: ");
  Serial.print(rpm);
  Serial.print("  Count: ");
  Serial.print(counter);
  Serial.print("  Time: ");
  Serial.println(elapsedTime);
}

void countPulse() {
  counter++;
}