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[on:]

hi there just looking into using a hall sensor on my arduino and came across this code below, i dont know if im being blind but where does it state which input pin its using?

Code:

const int ledPin = 13;
volatile int rpmcount;
int sensorState = 0;
unsigned int rpm;
unsigned long timeold;

void rpm_fun()
 {
      rpmcount++;
      digitalWrite(ledPin, HIGH);
      delay(50);
      digitalWrite(ledPin, LOW);
 }
 
void setup() {
  pinMode(ledPin, OUTPUT);     
  Serial.begin(9600); 
  attachInterrupt(0, rpm_fun, FALLING); 
}

void loop(){
 
   if(rpmcount>=5) {
      rpm=(60000*rpmcount)/(8*(millis()-timeold)); //the 8 changes to 4 if 4 magnets are used.
      timeold = millis();
      //Serial.println(rpmcount,DEC);
      rpmcount = 0;
      Serial.println(rpm,DEC);
   }
}

[Reply #1 on:]

Code:

attachInterrupt(0, rpm_fun, FALLING); 

Right there, pin 2.

[Reply #2 on:]

http://arduino.cc/en/Reference/AttachInterrupt

[Reply #3 on:]

There's a delay(50) in the ISR. Not a good idea.

 

[Reply #4 on:]

o ok i see thanks for that link one problem i can see is i am using an arduino uno and i will eventually need 3 hall inputs so how will i overcome that?

There's a delay(50) in the ISR. Not a good idea.

yes there is where it is blinking the led i dont actually need that led how can i get rid of that function as ive noticed if i remove void rpm_fun() i get a error

[Reply #5 on:]

yes there is where it is blinking the led i dont actually need that led how can i get rid of that function as ive noticed if i remove void rpm_fun() i get a error

You could remove the blinking by taking out the two lines of code that write HIGH and LOW to the ledPin, and the delay between them.

[Reply #6 on:]

ok so basically leave it there but take the internals out of it.

would this work or am i barking up the wrong tree?

Code:

volatile int rpmcount;
int sensorState = 0;
unsigned int rpm;
unsigned long timeold;
int rpm1 =1;


void setup() {
  Serial.begin(9600); 
 pinMode(INPUT, rpm1);
}
void loop(){
 
   if(rpm1>=5) {
      rpm=(60000*rpmcount)/(8*(millis()-timeold)); //the 8 changes to 4 if 4 magnets are used.
      timeold = millis();
      //Serial.println(rpmcount,DEC);
      rpmcount = 0;
      Serial.println(rpm,DEC);
   }
}

[Reply #7 on:]

"i will eventually need 3 hall inputs so how will i overcome that?"

You can have an interrupt on any pin, they are called PCINT.
See NickGammon's writeup on them here
http://www.gammon.com.au/forum/?id=11488

[Reply #8 on:]

You can keep the blinking led.
Move the blink part outside of the ISR. Set up a global byte variable and make it volatile to use as a blink flag, maybe call it bFlag. When the ISR runs, set that to 1 in the ISR. Then in loop() set up an if ( bFlag ) { } that makes the led blink and sets bFlag = 0.

So your ISR increments rpm count and flags the blink, it runs in next to nothing flat and is ready to service the next interrupt that fast.

IIRC you can set up any I/O pin to interrupt on Level Change. But look into things, maybe you don't need to use interrupts at all. Most things don't at 16 MHz.

You'd do better to learn how to use timers to run multiple tasks without using blocking code.
This is Nick Gammon's site, he's a master at explanations.
http://www.gammon.com.au/forum/?id=11411

[Reply #9 on:]

would this work or am i barking up the wrong tree?

Wrong tree entirely. You have completely removed the interrupt handler now.

In your original sketch, this interrupt handler was called when you got a falling edge on pin 2:

Code:

void rpm_fun()
 {
      rpmcount++;
      digitalWrite(ledPin, HIGH);
      delay(50);
      digitalWrite(ledPin, LOW);
 }

These are the lines of code that turn ledPin HIGH, wait 50 milliseconds and then turn it LOW again:

Code:

      digitalWrite(ledPin, HIGH);
      delay(50);
      digitalWrite(ledPin, LOW);

If you take those three lines out it will no longer flash the LED and will no longer have that unwise delay() in the interrupt handler.

[Reply #10 on:]

hi thanks for your replies on that link http://www.gammon.com.au/forum/?id=11488 there is a lot of stuff on that website to get your head wrapped around lol i have come up with this compiles fine but somethings telling me im missing something here?

Code:

volatile int rpmcount;
int sensorState = 0;
unsigned int rpm;
unsigned long timeold;


ISR (PCINT2_vect)
 {
 // handle pin change interrupt for D0 to D7 here
 }  // end of PCINT2_vect


void setup ()
  {
  Serial.begin(9600); 
  // pin change interrupt (example for D0)
  PCMSK2 |= _BV (PCINT16);  // want pin 0
  PCIFR  |= _BV (PCIF2);   // clear any outstanding interrupts
  PCICR  |= _BV (PCIE2);   // enable pin change interrupts for D0 to D7
  }

void loop(){
 
   if(rpmcount>=5) {
      rpm=(60000*rpmcount)/(8*(millis()-timeold)); //the 8 changes to 4 if 4 magnets are used.
      timeold = millis();
      //Serial.println(rpmcount,DEC);
      rpmcount = 0;
      Serial.println(rpm,DEC);
   }
}

p.s i dont wont the led output

[Reply #11 on:]

somethings telling me im missing something here?

How about something to update rpmcount ?

[Reply #12 on:]

Code:

volatile int rpmcount;
int sensorState = 0;
unsigned int rpm;
unsigned long timeold;


ISR (PCINT2_vect)
 {
   rpmcount;
 // handle pin change interrupt for D0 to D7 here
 }  // end of PCINT2_vect


void setup ()
  {
  Serial.begin(9600); 
  // pin change interrupt (example for D0)
  PCMSK2 |= _BV (PCINT16);  // want pin 0
  PCIFR  |= _BV (PCIF2);   // clear any outstanding interrupts
  PCICR  |= _BV (PCIE2);   // enable pin change interrupts for D0 to D7
  }

void loop(){
 
   if(rpmcount>=5) {
      rpm=(60000*rpmcount)/(8*(millis()-timeold)); //the 8 changes to 4 if 4 magnets are used.
      timeold = millis();
      //Serial.println(rpmcount,DEC);
      rpmcount = 0;
      Serial.println(rpm,DEC);
   }
}

better?

[Reply #13 on:]

better?

No try:-

Code:

rpmcount++;

[Reply #14 on:]

You started with a sketch that did more or less what you wanted, in a fairly simple way - no messing with hardware registers and so on.

Why have you thrown that away and started again with a more complex approach?