float rps[4]={0.00,0.00,0.00,0.00};
long int PRINT_PERIOD = 1000;
long int lastTimePrinted = 0;


void setup(){

 Serial.begin(9600);

 DDRD &= ~_BV (7); // pinMode (7, INPUT);       // rps_1
 DDRB &= ~_BV (0); // pinMode (8, INPUT);       // rps_2
 DDRC &= ~_BV (1); // pinMode (A1, INPUT);      //  rps_3
 DDRD &= ~_BV (2); // pinMode (2, INPUT);       //  rps_4

}


float rps_out(int k){

    static int lastReedState;
    static unsigned long lastTransition;
    static float rps_result;
    int reedState;
    unsigned long now;
    unsigned long revolutionTime;

   if ( k == 1 )     reedState = (PIND & _BV (7)) == 0; // digitalRead (7);
   else if ( k==2 )  reedState = (PINB & _BV (0)) == 0; // digitalRead (8);
   else if ( k==3 )  reedState = (PINC & _BV (1)) == 0; // digitalRead (A1);
   else if ( k==4 )  reedState = (PIND & _BV (2)) == 0; // digitalRead (2);

    // On a rising transition of the reed switch:
    if (reedState == HIGH && lastReedState == LOW) {                   // HIGH  LOW   measuring the low period    // LOW HIGH measuring the high period
        // Compute time since last valid transition.
         now = micros();
         revolutionTime = now - lastTransition;       // measuring the High period


        // Remember this transition.
        lastTransition = now;

    }

    // Remember last state.
    lastReedState = reedState;

   return rps_result;

}


void loop() {

   rps[0] = rps_out(1);
   rps[1] = rps_out(2);
   rps[2] = rps_out(3);
   rps[3] = rps_out(4);

    if (millis() - lastTimePrinted >= PRINT_PERIOD) {


     Serial.println(rps[0]);
     Serial.print('.');
     Serial.println(rps[1]);
     Serial.print('.');
     Serial.print(rps[2]);
     Serial.print('.');
     Serial.println(rps[3]);


      lastTimePrinted = millis();

     }


}