variable dimension

Using Arduino Programming Questions
#1

Hey!
I have to ask about my lack in programming.
I want to measure the duty cycle of a PWM.

int incomingAudio;//storage for A0 data
int pin = 8;
unsigned long duration;
int PERIODO = 20400; //period in microsecond
double duty =0;
int tau = 0;

void setup(){
  
pinMode(pin, INPUT);
Serial.begin(9600);
}

void loop(){
 incomingAudio = analogRead(A0); 
  
  //do other stuff here
 analogWrite(3,incomingAudio >> 2);
 
   tau = pulseIn(pin, HIGH);
   duty = (tau/PERIODO)*100;
   Serial.println(tau);
   Serial.println(duty);
   delay(1000);
}

pulseIn is in micro right? the frequency of my PWM should be 20,40ms so I chqnged it in micro.

the result sometimes is higher then 2. how come?
Thqnk you!!!

#2

What sort of values are shown for "tau"?

tau = pulseIn(pin, HIGH);

"pulseIn" returns "unsigned long", but "tau" is an "int".

#3

You're doing integer division here:

   duty = (tau/PERIODO)*100;

Either make tau float or at least multiply first:

   duty = tau * 100 / PERIODO ;

or you'll simply see zero

#4 
int PERIODO = 2040; //period in microsecond
float duty =0;
unsigned long tau = 0;

 tau = pulseIn(pin, HIGH);
   duty = tau * 100/ PERIODO ;

And I obtain for tau 190 175 47 88
For duty: 2.00 7.00 14.00 ect

I change the PERIODO putting one wero less.
my PWM frequency is 20.40ms I measured it with the oscilloscope. And PulseIn is in micro.. so I think the right period should be 20400. but there is one mistake.

#5

You're only measuring the HIGH portion of your PWM cycle, aren't you?

Why is this thread called "variable dimension"?

#6

I am not English mother tounge and I what I meant by Dimension was long int char ect.
SO I wanted clarified first of all that.
And I needed to find the right variable "dimension" in order to proceed with my project... measure of duty cycle! :slight_smile:

#7

"Type of variable" or "data type" :slight_smile:

#8

Thank you a lot Hackscribble!!!!
:slight_smile:

#9