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1. 

   doctorzaius
   Member

   I think the external interrupts on my maple aren't working and this is why:

   1) I connected pin 2 and pin 9.

   2) I wrote a program that installs an interrupts handler for pin 2 and generates a square wave using pin 9.

   3) when the program runs, the interrupt handler never gets invoked. The same program works on my Arduino UNO. Here it is:

   /*
   * Interrupt test
   */

   const int analogOutPin = 9; //Pin 9 and Pin 2 are wired together.
   const int analogInPin = 2;

   volatile int count = 0;

   void setup()
   {
   pinMode (analogOutPin, OUTPUT);
   pinMode (analogInPin, INPUT);
   attachInterrupt (0, handler, RISING);
   }

   void handler ()
   {
   count++;
   }

   void loop() {
   digitalWrite (analogOutPin, HIGH);
   delay (50);
   digitalWrite (analogOutPin, LOW);
   delay (50);
   SerialUSB.print (count);
   SerialUSB.print ("\n");
   }

   What am I doing wrong?

   Posted 5 years ago #
2. 

   perry
   Administrator

   hi,

   change attachInterrupt (0, handler, RISING) to:

   attachInterrupt (analogInPin, handler, RISING);

   Posted 5 years ago #
3. 

   mikep
   Member

   I am not clear on why the call to attachInterrupt needs to be changed from "0" to "analogInPin"?
   I was looking at the documentation for "attachInterrupt" http://leaflabs.com/docs/lang/api/attachinterrupt.html and it seems a bit confusing to me.
   First, the documentation of the method signature only lists 2 parameters, not three.
   Also, it talks about valid values from 0 to 4 for the first parameter (channel).
   How does one know which "channel" belongs to which Pin?
   Or is a channel the same as an EXTI line, and we can use this document here to determine which channel to use with which pin:
   http://leaflabs.com/docs/external-interrupts.html#external-interrupts

   So that document says that Pin2 would actually be EXTI0 (channel 0)?
   The example uses channel 0 for Pin13, so that is different too.

   Or is the attachInterrupt method actually translating the pin number into the appropriate channel etc or am I completely looking at this the wrong way?

   Thanks for any insights...

   Posted 5 years ago #
4. 

   General Tree
   Member

   "On the Maple, you don’t have to remember which interrupt number goes with which pin – just tell attachInterrupt() the pin you want." (quote from http://leaflabs.com/docs/lang/api/attachinterrupt.html#id3 )

   This means that if you want to attach an interrupt to pin #2, you need to write

   attachInterrupt(2,handler,CHANGE);

   regardless of the EXTIx channel the pin is connected to (for this pin, its EXTI0).
   However, it means that once you attached an interrupt to pin #2, you can not attach an external interrupt to pins 15 and 27, since they too share the EXTI0 channel.

   As for the example, what it does is it reads the state on pin #0 and turns on/off the led on pin #13 accordingly. It would be pointless to attach the interrupt to pin #13, and then change pin #13 according to itself.
   I hope that cleared things a bit.

   Posted 5 years ago #
5. 

   mikep
   Member

   Ok, thank you, I see that sentence now.
   So the documentation above seems to just be a little bit out of date where it says:

   Parameters
   
       * channel - the channel to attach the ISR to, from 1 to 4.
       * handler - The ISR to attach to the given channel.

   It's nice that libmaple does all the translation from PIN to the ISR for us.
   Thanks again,
   Mike

   Posted 5 years ago #

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