Using Interrupts « LeafLabs Garden

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Using Interrupts

(6 posts) (2 voices)

Started 3 years ago by Bernardo769
Latest reply from gbulmer

Hi,

in this example :

volatile int state = LOW; 

void setup() {
    pinMode(BOARD_LED_PIN, OUTPUT);
    pinMode(20, INPUT);
    attachInterrupt(20, blink, CHANGE);
    pinMode(21, INPUT);
    attachInterrupt(21, blink, CHANGE);
}

void loop() {
    digitalWrite(BOARD_LED_PIN, state);
}

void blink() {

  // test pin has an interrupt
  // ?????

    if (state == HIGH) {
        state = LOW;
    } else { // state must be LOW
        state = HIGH;
    }
}

Blink function is attached to two interruptions for pins 20 and 21 :

attachInterrupt(20, blink, CHANGE);
    attachInterrupt(21, blink, CHANGE);

In the blink function, is it possible to know what has triggered the interrupt pin?

Thank you for your answers

Posted 3 years ago #

gbulmer
Moderator
Bernardo769 -

In the blink function, is it possible to know what has triggered the interrupt pin?

I don't think I understand the question.

Are you asking:
A. "can the interrupt service routine (blink) work out which pin triggered the interrupt that called the (blink) function", or
B. "what kind of signal triggered the pin, was it a rising edge, falling edge, ..." or
C. something else?

BTW
```
void blink() {

  // test pin has an interrupt
  // ?????

    if (state == HIGH) {
        state = LOW;
    } else { // state must be LOW
        state = HIGH;
    }
}
```
can be rewritten as:
```
void blink() {

  // test pin has an interrupt
  // ?????
  state = !state;
}
```
Posted 3 years ago #

Bernardo769
Member

Sorry if I was not specific enough.
I rephrase my question:

volatile int state_pin20 = LOW;
volatile int state_pin21 = LOW; 

void setup() {
    pinMode(BOARD_LED_PIN, OUTPUT);
    pinMode(20, INPUT);
    attachInterrupt(20, blink, CHANGE);
    pinMode(21, INPUT);
    attachInterrupt(21, blink, CHANGE);
}

void loop() {
    digitalWrite(BOARD_LED_PIN, (state_pin20 || state_pin21));
}
void blink() {
  // test pin has an interrupt

  if (pin20) {  // How to test here to see the pin20 triggered interrupt? ...
        state_pin20 = !state_pin20;
    }

  if (pin21) {  how to test here? ...
        state_pin21 = !state_pin21;
    }
}

thank you for your help

Posted 3 years ago #

gbulmer
Moderator
Bernardo769 - figuring out which pin triggered an interrupt can be a bit involved.

The easiest way is to have a different interrupt handler for each pin:
```
volatile int state_pin20 = LOW;
volatile int state_pin21 = LOW; 

void setup() {
    pinMode(BOARD_LED_PIN, OUTPUT);
    pinMode(20, INPUT);
    attachInterrupt(20, blink, CHANGE);
    pinMode(21, INPUT);
    attachInterrupt(21, blink, CHANGE);
}

void loop() {
    digitalWrite(BOARD_LED_PIN, (state_pin20 || state_pin21));
}
void blink20() {
  // pin had interrupt

        state_pin20 = !state_pin20;
}
void blink21() {
  // pin had an interrupt
        state_pin21 = !state_pin21;
}
```
Could you ue that approach?

If not, you need to look in EXTI_PR register.
The way interrupt pins are set up is a bit odd. There is not a unique pin interrupt id for every pin.

I/O pins are grouped into 16-pin ports, and a Maple has several ports.
To figure out which pin has triggered, you'll need to figure out which port, and pin within that port, a Maple pin number corresponds to.

There is a table at http://leaflabs.com/docs/hardware/maple.html#gpio-port-pin-map
which tells you.

IIRC, all the pin 0's on all ports share 1 set of trigger control and flags.
All the pin 1's on all ports share a 2nd set of trigger control and flags.
and so on
So once you know the pin number within the port, you can check that flag within EXTI_PR.
This is all described in loving detail in the STM32F103 RM0008 manual, which you can download from ST Micro.
Posted 3 years ago #

Bernardo769
Member

Thank you for your clarification.
I noticed that determine which pin triggered an interrupt can be a bit complicated.
My knowledge of register management are limited. I do not engage in this way for now. But if there is a tutorial to do some testing, I'm interested.

I looked for a solution using C++ classes:

#include "voieRC.h"
#define Serial SerialUSB

voieRC bouton(20);

void setup() {
  attachInterrupt(20, bouton.*ptr, CHANGE);
  // Ne fonctionne pas : error: invalid use of non-static member function
}

void loop() {
  SerialUSB.println(bouton.valeur());
  delay(500);
}

voieRC::voieRC(int pin){
  pinRC = pin;
  pinMode(pin, INPUT_PULLUP);
}

unsigned int voieRC::valeur() const{
  return (timeDOWN - timeUP);
}

void voieRC::etat() {
  if (digitalRead(this->pinRC) == HIGH) {  // Front montant
    timeUP = micros();
    timeDOWN = micros();
  }
  else {  // Front descendant
    timeDOWN = micros();
  }
}

With voieRC.h =

class voieRC{
  public:
  voieRC(int);

  unsigned int valeur() const;
  void etat();

  private:
  int pinRC;
  unsigned int timeUP;
  unsigned int timeDOWN;
};

I get a compilation error:

attachInterrupt(20, bouton.*ptr, CHANGE);
  // error: invalid use of non-static member function

I tried to "cast" the pointer recover:

void (voieRC::*ptr)() = &voieRC::etat; //On déclare un pointeur sur la fonction membre
voieRC bouton(20);

void setup() {
  void (*ptrw)() = (void (*)()) bouton.*ptr;
  // Ne fonctionne pas : error: invalid cast from type 'voieRC' to type 'void (*)()'
  attachInterrupt(20, *ptrw, CHANGE);
}

But it does not.

Posted 3 years ago #

gbulmer
Moderator

Bernardo769 - There error message is accurate and complete.

There is no member of class voieRC called ptr, and if there were, it could not be a member, it must be a static member function, or pointer to a simple function.

Maybe you should solve the problem using C first, rather than introduce an extra source of bugs and misunderstanding?

Posted 3 years ago #

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