how to read pulses from an external interrupt on an arduino uno of every 20ms

Projects Programming
1

Hello everyone,

I am new to this forum and i have an problem with my project so plz help me to get out of it..I shall be very thankful to you.

actually i want to perform several task as follows:-

  1. i had connected an turbine sensor to digital pin 2 .

  2. now i want to count the no of pulses generated for every 20ms

  3. then i want to serially print those values after receiving 'a' on serial port.

below is my code i am using but having problem:-

#include "TimerOne.h"
int flowPin = 2;    
int x = 0;     
volatile int count = 0;   
char b ;
void setup()
 {
  pinMode(flowPin, INPUT);           //Sets the pin as an input
  pinMode(13,OUTPUT);
 
  Timer1.initialize(20000);
  attachInterrupt(0, Flow, RISING);
  Timer1.attachInterrupt(check);
  Serial.begin(9600);  
}

void loop()

{
        if (Serial.available() >0 )
    {
        b = Serial.read ();
 
    } 
 
}


void check()
{
  x= count;

    if (b == 'a')
     {
       Serial.println(x);
     }

  count = 0;
  
  }
 
void Flow()
{
   count++; //Every time this function is called, increment "count" by 1
}

with this code my result of serial.println(x) are not acuurate. So plz help in resolving this problem

2

with this code my result of serial.println(x) are not acuurate

How do you know ?

3

because the pulses generated are increasing and decreasing linearly.....but the result on serial monitor is non linear ..

while blowing continuesly air through turbine for several seconds....
i got the following result on serial monitor:-

0
0
0
0
0
0
0
4
10
23
7
1
0
0
0
0
0
3
0
0
0
0
0
0
0
0
0
0
0
0
0
2
3
1
5
4

4

I would just use micros() for the timing - something like this

void loop() {
   if (micros() - lastIntervalMicros >= 20000UL) {
      lastIntervalMicros += 20000UL;
      noInterrupts(); // pause interrupts to read and write multi-byte values
         pulsesThisPeriod = count;
         count = 0;
      interrupts();
      Serial.println(pulsesThisPeriod);
    }
}

...R