sketch_jun29a.ino.txt

//INPUT CAPTURE EXAMPLE
//measure frequency and pulse width

#define GEN_PIN 5
#define ICP_PIN 48
#define OUT_PIN 12

                        // some variables to help see that something is happening in the interrupt handlers
volatile unsigned int Value = 0;     // this stores the current ICR1 value

volatile unsigned int Overflows = 0;
volatile unsigned int PulseCount = 0;
unsigned int prevPC = 0;
unsigned int prevMs = 0;

/* Overflow interrupt vector */
ISR(TIMER4_OVF_vect){                 // here if no input pulse detected 
   Overflows++;                       // incriment overflow count  
}

/* ICR interrupt vector */
ISR(TIMER4_CAPT_vect){
   TCNT4 = 0;                            // reset the counter  
   if( bit_is_set(TCCR4B ,ICES1)){       // was rising edge detected ?   
        digitalWrite(OUT_PIN,HIGH );      // yes, set our output pin high to mirror the input
   }
   else {                                // falling edge was detected 
        Value = ICR4;                    // save the input capture value 
        digitalWrite(OUT_PIN,LOW );       // set our output pin low to mirror the input  
        PulseCount++;
            
   }     
   TCCR4B ^= _BV(ICES1);                 // toggle bit value to trigger on the other edge    
}



void setup() {
  Serial.begin(115200);
  
  // put your setup code here, to run once:
  pinMode(GEN_PIN, OUTPUT);
  pinMode(OUT_PIN, OUTPUT);
  pinMode(ICP_PIN, INPUT);                // ICP pin (digital pin 8 on arduino) as input



  TCCR4A = 0 ;                    // this register set to 0!
  TCCR4B =_BV(CS11);              // NORMAL MODE!!, prescaller 8, rising edge ICP1 - this works
  TCCR4B |= _BV(ICES1);           // enable input capture     

  TIMSK4 =  _BV(ICIE1);                         // enable input capture interrupt for timer 1
  TIMSK4 |= _BV(TOIE1);                         

  prevMs = millis();
}

void dump() {
  Serial.print("count:");
  Serial.print(PulseCount);
  Serial.print(", ovflows:");
  Serial.print(Overflows);
  Serial.print(", val:");
  Serial.println(Value);
  
}



void loop() {
  // put your main code here, to run repeatedly:
  int vals[] = {30, 40, 50, 60, 120, 190, 50, 10};


  delay(100);
  //Serial.print("V:");
  Serial.println(Value);
  return;
  for (int i=0; i<sizeof(vals)/sizeof(int); i++) {
    Serial.print("Setting pwm:");
    Serial.println(vals[i]);
    analogWrite(GEN_PIN, vals[i]);
    for (int j=0; j<4; j++) {
      delay(1000);
      dump();    
      unsigned int m = millis();
      unsigned int dc = PulseCount - prevPC;
      float mc = (float) (m - prevMs) / 1000.0;
      float frq =  (float) dc / mc;
      Serial.print("frq:");
      Serial.println(frq);
      
      prevPC = PulseCount;
      prevMs = m;
    }
  }
}