Instant Interrupts - Revisited

[WOZZY-2010]

Well I think I've finally figured out some of the nuances of RBC_INT.
I think the last example I tried to use was not a very good way to test it out.

I tried to document this working code example in a way that's understandable and can be used as a template to build on.

This is setup with PBP type interrupts using ReEnterPBP-18.bas, since I'm using PBP in the Interrupt handler, but ... it seems to work just fine when run as ASM type, and not including ReEnterPBP-18.bas. You can just uncomment out the appropriate lines to suit your needs.

The thing that was giving me so much of a headache before was the need to read one of the Port B <4-7> registers prior to exiting the Interrupt handler. This ends the mismatch condition and allows the RB Port Change Interrupt Flag Bit to be cleared. Even though I was reading the Port B <4-7> registers frequently, it seems that using GOTO to enter the Interrupt handler exit subroutine, caused the Interrupt Flag Bit to reset.

Program operation:
This Program uses DEBUG to send status comments to a 9600 Buad Serial ASCII Terminal on PORTC.6
On first press of any of the PORTB<4-7> buttons, the program enters the interrupt handler.
The Interrupt Handler, continuously reads the buttons.
Buttons 1,2 & 3 just display a status message. You could put any subroutine in place of the DEBUG Statement.
Button 4 gracefully exits the interrupt handler.
At this point, RBC_INT is reset and awaiting any PORTB<4-7> button press again to reenter the Interrupt handler.


Anyway here's the Code and a schematic of the setup... I hope this helps someone who's struggling with RBC_INT like I was.
The ZIP file attachment has the code, and copies of the version of DT_INTS-18.bas and ReEnterPBP-18.bas that are included.

Bob W.

' RBC TEST.BAS
' Bob Wozniak
' PIC 18F6480 @ 20 MHZ
' MPLAB IDE V8.40  /  PBP V2.60  /  Build Options: [-ampasmwin]
' RB4  Momentary Contact Button Goes High on Press,  10K Resistor to Ground
' RB5  Momentary Contact Button Goes High on Press,  10K Resistor to Ground
' RB6  Momentary Contact Button Goes High on Press,  10K Resistor to Ground
' RB7  Momentary Contact Button Goes High on Press,  10K Resistor to Ground
' RC6  22K ohm to RX on 57600-N-8-1 Serial Terminal
' This program created to check Port-B Change Interrupts

INCLUDE "DT_INTS-18.bas"		  ; Include Darrel Taylor's Base Interrupt System for PIC18F [Version:3.4 (NOV 04, 2009)]
INCLUDE "ReEnterPBP-18.bas"      ; Need to include if using PBP type interrupts

DEFINE OSC 20

DEFINE DEBUG_REG PORTC	' SETUP DEBUG to view output on 9600 BAUD ASCII Terminal on PORTC.6
DEFINE DEBUG_BIT 6 			
DEFINE DEBUG_BAUD 9600
DEFINE DEBUG_MODE 1 

I VAR WORD
X VAR BYTE

ASM
INT_LIST  macro ; IntSource,  Label,             Type, ResetFlag?
;       INT_Handler RBC_INT, _RBC_INT_HANDLER,   ASM,  no             ; use for ASM type interrupts
        INT_Handler RBC_INT, _RBC_INT_HANDLER,   PBP,  no             ; use for PBP type interrupts
    endm
    INT_CREATE
ENDASM
@ INT_ENABLE   RBC_INT



HOLD_HERE:          ' **** This subrouting loops continuously and waits for button press to activate RBC interrupt handler
IF I = 0 THEN DEBUG 10,13,10,13,"HOLDING FOR PORTB <4-7> BUTTON PRESS to ACTIVATE INTERRUPT",10,13 : I = 1
PAUSE 10
GOTO HOLD_HERE



RBC_INT_HANDLER:     ' **** Program jumps here when ANY PORTB.4 thru PORTB.7 are changed ****
DEBUG "############### RBC INTERRUPT ACTIVATED #################",10,13
PAUSE 250    ' This pause allows time for button debounce - needs to be here unless immediate read of interrupt button req'd


READ_BUTTONS:        ' **** Program cycles reading buttons, until button 4 is pressed ****
If PORTB.4 = 1 Then DEBUG "BUTTON 1 PRESSED",10,13
If PORTB.5 = 1 Then DEBUG "BUTTON 2 PRESSED",10,13
If PORTB.6 = 1 Then DEBUG "BUTTON 3 PRESSED",10,13
If PORTB.7 = 1 Then DEBUG "BUTTON 4 PRESSED - EXITING",10,13 : I = 0 : GOTO END_RBC_INT
PAUSE 5  
GOTO READ_BUTTONS


END_RBC_INT:        ' **** this subroutine gracefully exits the interrupt handler and resets for next RBC event ****
PAUSE 250              ; This pause allows time for button debounce - needs to be here or interrupt will immediatly reactivate
DEBUG "################ EXITING RBC INTERRUPT HANDLER ############",10,13

X = PORTB.7            ; NOTE: Prior to returning from RBC Interrupt, you MUST read at least 1 PORTB <4-7> to end
                       ; the mismatch condition and allow the RB Port Change Interrupt Flag Bit to be cleared.
                       ; If not here, the interrupt will immediatly reactivate if using the GOTO END_RBC_INT statement.
@ INT_CLEAR RBC_INT
@ INT_ENABLE RBC_INT
@ INT_RETURN
END