Can I have interupts on any pin ?

[Bonxy]

Hi All

1. Can I have interupts work on any pin ? (so that i can detect when a pin changes state)

2. Can i have multiple interupts ? (one for each pin so that i can trigger diffrent iterupt handlers depending on which pin changes state)

Anyone know how to do this (on 18f4550)

Thx

[rsocor01]

Bonxy,

Yes, you can have multiple interrupts. Can you have an interrupt work on any pin on a PIC18F4550? I don't know about that. But can you create a routine where you check the status of the pins that you want and then if a change is made goto to a sub-routine? Something like

IF PORTX.0 = 1 THEN GOTO SUBROUTINE0
IF PORTX.1 = 1 THEN GOTO SUBROUTINE1
.......

Robert

[sayzer]

Use RB.0 for interrupt pin and connect as many normal pin as you want to this pin via a diode.

RB0 will interrupt with any of the pins; you will check the status of the pins in interrupt routine.

Thus, if you connect 10pins with RB0, then you will have 10 interrupt pins.

____________________________________

[Acetronics2]

Hi, Bonxy

You always can use the old method : use an " OR " gate to trigger one interrupt pin of the device.
after, read ports and just check your inputs as rsocor01 tells, hoping they didn't change state in between ... ( possible issue ... but ...)

note a couple of MCP 23016 or 23S17 ( Port expanders ) could help a lot here ...

the question is here : really need it ???

Alain

[Charles Linquis]

Or - if you can tolerate a little latency -

You can use a fast timer interrupt (say 1mSec) and check the status of any pin in that interrupt.

[Bruce]

Can I have interupts on any pin ?

No. You can't have interrupts on any pin. Only pins that have some type of associated interrupt will cause a hardware interrupt.

Testing inputs pins for high or low logic states is not a hardware interrupt.

[Charles Linquis]

This is an example of what I mentioned earlier.

I'll call it FAKE INTERRUPT

It does have a latency of a little over a millisecond, but often it is plenty good enough to do what you need done. You can make the interrupt faster if you wish - but remember each time you enter/leave an interrupt, you are stealing quite a few processor cycles.


This code will check the status of any pin once per millisecond. It was written for an 18Fxxxx at 40Mhz. This example is checking the status of PORTC.0.

    Changed VAR BYTE
     OldPort VAR BYTE
      
     T0CON = %10001000 ; turn it on, 16 bits, no prescaler (osc/4)
        
     CLEAR 


'-----------------  DT_INTS section ----------------------------        
       
        INCLUDE "DT_INTS-18.bas"        
        INCLUDE "ReEnterPBP-18.bas"     
ASM
     INT_LIST  macro    ; IntSource,        Label,  Type, ResetFlag?
              INT_Handler    TMR0_INT,   _FakeInt,   PBP,  yes 
          endm
    INT_CREATE           
ENDASM


Goto OverInt

'------------------ Timer 0 interrupt handler-----------------------------------


FakeInt:
        
         TMR0H = $D8  ; Preload depends on clk speed
         TMR0L = $F7  ; One millesecond timeout at 40Mhz. 
                      ; Always load HIGHBYTE FIRST
                              
         Changed = PortC ^ OldPort 
         IF Changed.0 = 1 THEN     ; Pick your pin
             OldPort = PortC
             ;;;;  Whatever you want to do when Port bit changes
         ENDIF     
         
@ INT_RETURN         


Overint:
  
  OldPort = PortC    ; Init the var

@ INT_ENABLE TMR0_INT


NormalProgramLoop:

   

    Goto NormalProgramLoop
   
  END