Hi all,

I am having some trouble getting a simple program using the Interrupt on change function.

Here is my hardware setup:

PIC18F2550, 4MHz Crystal. LEDs attached on PORTA<0:3>, push button on PORTB.4. I am using the EasyPIC6 dev board from Mikro Electronika so all of the connections are definately correct.

The software is written in Picbasic Pro using Microcode Studio and includes the use of Darrell Taylors Instant Interrupts.

The program is ultimately very simple:

Turn on LED on A.1
Initialise the USB connection
Turn on LED on A.0 (and off on A.1)
Enter a loop in which the USB connecton is serviced approximately every 5ms and set LED on A.3 to status of B.4 (this is to confirm to me that the program is still running)

When the interrupt on change on PORTB is detected it sets A.2 LED to the status of B.4.

However the program for some reason does not function correctly. One of two things happens when the button is pressed: Either A.2 stays off (but A.3 follows the button press so the program is running correctly but the interrupt does not seem to be firing.) or all the LEDs turn off and don't come back at all until the device is reset.

I just cannot figure this out at all! If anyone can help it could be greatly appreciated.

Since im certain this is a code issue I have attached it below:

 ==============================================================================
' PIC Configuration Bits
' ==============================================================================
 
 
  asm
    __CONFIG    _CONFIG1L, _PLLDIV_1_1L & _CPUDIV_OSC1_PLL2_1L & _USBDIV_2_1L  
                            ;              ;                      ; USB clock source comes from the 96 MHz PLL divided by 2
                            ;              ; [OSC1/OSC2 Src: /1][96 MHz PLL Src: /2]
                            ; No prescale (4 MHz oscillator input drives PLL directly)
 
    __CONFIG    _CONFIG1H, _FOSC_XTPLL_XT_1H & _FCMEN_OFF_1H & _IESO_OFF_1H 
                            ;                  ;               ; Oscillator Switchover mode disabled
                            ;                  ; Fail-Safe Clock Monitor disabled
                            ; XT oscillator, PLL enabled, XT used by USB
    __CONFIG    _CONFIG2L, _PWRT_ON_2L & _BOR_ON_2L  & _BORV_2_2L  & _VREGEN_ON_2L   
    __CONFIG    _CONFIG2H, _WDT_OFF_2H 
    __CONFIG    _CONFIG3H, _MCLRE_ON_3H & _LPT1OSC_OFF_3H & _PBADEN_OFF_3H & _CCP2MX_OFF_3H 
    __CONFIG    _CONFIG4L, _STVREN_ON_4L & _LVP_OFF_4L ;& _ICPRT_OFF_4L  & _XINST_OFF_4L & _DEBUG_OFF_4L 
    endasm
 
DEFINE OSC 48
INCLUDE "DT_INTS-18.bas"        ' Base Interrupt System
INCLUDE "ReEnterPBP-18.bas"     ' Include if using PBP interrupts
 
' ==============================================================================
' Constants and Variables Definition
' ==============================================================================
USBBufferSizeMax   con 3  ' maximum buffer size
USBBufferSizeTX    con 3  ' input 
USBBufferSizeRX    con 3  ' output
 
' the USB buffer...
USBBuffer        Var Byte[USBBufferSizeMax] 
USBBufferCount   Var Byte
 
 
' Used by USB initialisation:
usb_device_state        var byte EXT
CONFIGURED_STATE        CON EXT
 
' Used in USB Comms
IDLEIF                  VAR UIR.4
SOFIF                   VAR UIR.6
Plugged                 VAR BIT 
 
 
InputPin VAR PORTB.4                ' the Input on which edges are detected
InputStatusLED var PORTA.2        ' the status of InputPin is mirrored here
StatusLED_Pin1 var PORTA.0          ' Bicolour Device Status LED pin1
StatusLED_Pin2 var PORTA.1          ' Bicolour Device Status LED pin2
tempbyte var byte
temp var bit
 
==============================================================================
' Hardware configuration
' ==============================================================================
    TRISA = 0                   ' all outputs
    TRISB = %00010000' only RB4 as input so others are excluded from IOC
    TRISC = 0                   ' all outputs
    PORTA = 0                   ' set all LEDs off at startup
    PORTB = 0
' ==============================================================================
' A/D converter
' ==============================================================================
'         
    ADCON0  =   %00000000       ' A/D converter module disabled
    ADCON1  =   %00001111       ' PORTA all digital signals
' ==============================================================================
' USB module
' ==============================================================================
    ucfg    =   %00010100       ' enable internal USB pull-up, Full speed USB
' ==============================================================================
' ASSEMBLER MACROS
' ==============================================================================
'
' HIGH Priority Interrupt processor macro
'
' Change on PORTB interrupt to transmit input status only on change
ASM
INT_LIST  macro    ; IntSource,          Label,  Type, ResetFlag?
        INT_Handler    RBC_INT,  _ChangeOnPortB,   PBP,  yes
    endm
    INT_CREATE               ; Creates the interrupt processor
 
endasm
 
==============================================================================
' MAIN PROGRAM
' ==============================================================================
 
    StatusLED_Pin2 = 1
    StatusLED_Pin1 = 0  
 
gosub InitialiseUSB                ' Initialise the USB
 
    StatusLED_Pin2 = 0
    StatusLED_Pin1 = 1  
 
 
 
@   INT_ENABLE  RBC_INT         ; Enable the RBC Interrupt
 
 
ProgramStart:
                    ' Sit in a loop waiting for interrupts to occur
    USBSERVICE
    pause 5
    PORTA.3 = InputPin   
goto ProgramStart 
 
 
' ==============================================================================
' ROUTINES ==========================================================
' ==============================================================================
 
ChangeOnPortB:
@   INT_DISABLE RBC_INT    
    tempbyte = PORTB                ' read portb to update the change latch
    InputStatusLED = InputPin
@   INT_ENABLE RBC_INT
@   INT_RETURN
 
 
InitialiseUSB:
    
    pause 500
    
    usbinit ' initialise USB...
    repeat  ' kick-start it by performing a tight loop of servicing until the USB
            ' state is CONFIGURED (Darrell Taylors method)
        usbservice
    until usb_device_state = CONFIGURED_STATE

return

 

Thanks for the quick response Alberto but if only it were that simple! The interrupt is enabled just after the USB Initialisation routine so I'm afraid that is not the solution.

Cheers

Andy

 

I did not think you had to enable them directly after the declaration since in DTs USB interrupts examples he does not enable the USB Service interrupt until after USB initialisation.

Anyway I tried it just in case and also stripped out the USB stuff to see if this would help too. It did work, but as soon as I put the USB stuff back in it just turns all LEDs off when the button is pressed. I attempted to remove the USB stuff to get back to a known working state but it continues to just turn the LEDs off - I truly dont understand this!