//#include <SPI.h>
//#include <Wire.h>
#include <Adafruit_GFX.h>
#include <Adafruit_SSD1306.h>
#include <Fonts/FreeSerif9pt7b.h>
#include "PinChangeInterrupt.h"


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

#define HallPin 2

struct SpeedCount
{
  volatile bool fresh;
  volatile long sign;
  volatile long lastTime;
 
};

SpeedCount speedCount;
// Declaration for an SSD1306 display connected to I2C (SDA, SCL pins)
Adafruit_SSD1306 display(SCREEN_WIDTH, SCREEN_HEIGHT, &Wire, -1);



void Hall_ISR()
{
  speedCount.sign = micros() - speedCount.lastTime;
  speedCount.lastTime =  micros();
  speedCount.fresh = true;

}
  
 

void setup() 
{
  //Serial.begin(115200);

  attachInterrupt(digitalPinToInterrupt(HallPin), Hall_ISR, FALLING); 
   display.begin(SSD1306_SWITCHCAPVCC, 0x3C);

  display.setFont(&FreeSerif9pt7b);
  display.clearDisplay();
  display.setTextSize(1);             
  display.setTextColor(WHITE); 
  display.setCursor(0,10); 
  display.println("HALL sense");      
  display.setCursor(0,30); 
  display.println("Speed control"); 
  display.display();
 
}
void loop() 
{
  if(speedCount.fresh )
  {
    display.clearDisplay();
    display.setCursor(0,20);        
    display.print(60000000.0/speedCount.sign);
    display.println(" rpm");
    display.display();
    speedCount.fresh = false;
  }
 
  //delay(1000); 
}