PIC16F684 Program question


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  1. #1
    Join Date
    Dec 2006
    Posts
    9

    Question PIC16F684 Program question

    Below I've included the program that I have a question about. Essentially the program is meant to interrupt operation of a transmitter when a switch is turned from ON to OFF position. The switch in this case is a reed relay which turns ON and OFF using a magnet. The switch is connected to PORTA1 of my PIC however when the switch is turned OFF the interrupt does not work.
    I tried to write an interrupt routine the easy way by using loops in all my subroutines to make sure that am testing the PORTA1 value at least once a second. HOwever this has not solved the issue.
    Therefore mine is a two part question: the major part is how come when the voltage on PORTA1 drops from 2.8V to 0.3V is the program not executing like its supposed to. During program execution, if I ground PORTA1, the program works as supposed to.
    The second part is I'd like to use Interrupts instead of adding the loops to my program and how can I make that part work. I have included the interrupt at the bottom of the code. Any assistance will be greatly appreciated.





    '************************************************* ********
    '* Notes : This test makes sure that the interrupt is working *
    '* '************************************************* ****
    ; Define statements.
    define OSC 20 ;every MPU used is 20mhz
    DEFINE INTHAND ReedIntHandler

    ;Assembly Language Interrupt storage
    wsave VAR BYTE $70 system ;addresses $70-$7F are the same for all banks
    ssave VAR BYTE bank0 system
    psave VAR BYTE bank0 system

    'Port operation configurations
    CMCON0=%00000111
    VRCON=%00000000 'CVref turned off
    OPTION_REG=%10000111 'Disable PORTA pullups, set timer0 scaler to 1:256
    ANSEL=%00000000

    ; Program Variables
    Loop VAR BYTE ;general loop counter for LED flashing

    ; Constant definitions
    Outp CON 0
    Inp CON 1

    'Assign Ports to simple name
    LowVoltage VAR PortA.0 'Battery low voltage detection port
    ReedSwitchState VAR PORTA.1 'Reed Switch ON and OFF state line
    LED VAR PORTA.2 'Turn LED ON and OFF
    HoldTxON VAR PORTC.0 'Hold Tx ON when water contacts activated
    Tx_Data VAR PORTC.1 'Transmit Data Line
    Tx1_Enable VAR PORTC.2 'Transmit 121.5Mhz Line
    Tx2_Enable VAR PORTC.3 'Tranmit 156MHz Line
    MotorControl_1 VAR PORTC.5 'Activate Release Mechanism
    MotorControl_2 VAR PORTC.4 'Activate Latch Mechanism

    'Initialize port states
    TrisA.0=Inp 'set batt low voltage detection to input
    TrisA.1=Inp 'set Reedswitchstate to input
    TrisA.2=Outp 'set led transmission to output
    TrisC.0=Outp 'set HoldTxLine ON to output
    TrisC.1=Outp set Transmit data line to output

    Goto Main

    Main:
    low HoldTxON ; Initialize by turning clearing all the outputs
    low LED
    low Tx_Data

    if reedswitchstate then
    gosub lowvoltagecheck
    else
    pause 1000 ;Wait for a second to make sure the switch
    high holdtxon ;is not being held HIGH
    high reedswitchstate
    gosub Lowvoltagecheck
    endif

    gosub turnontransmitter
    gosub dtmftransmission
    end

    ;************************************************* **********************
    ; Subroutine to check for battery voltage at the beginning and end of
    ; transmission flashing to signify low voltage or high voltage (to be defined)

    LowVoltageCheck:
    If lowVoltage = 1 then ; If the battery voltage is OK
    high led
    for loop = 1 to 10 ; turn on the LED for 5 seconds
    pause 500
    gosub checkreedswitch
    next
    LOw LEd
    else
    for loop = 1 to 10 ; If the battery voltage is low
    high led ; Flash the LED 10 times
    Pause 250 ; at a rate discernable from the
    low led ; transmit LED flash rate
    pause 250
    gosub checkreedswitch
    next
    endif
    return
    '************************************************* ******************************
    CheckReedSwitch:
    if reedswitchstate then
    return
    else
    gosub turnofftransmitter
    endif
    Return
    ;************************************************* ******************************
    TurnOnTransmitter:
    high holdtxon ; Makes sure the Tx stays on after activation
    gosub checkreedswitch
    return
    ;************************************************* ******************************
    DTMFTransmission:
    ' DTMF transmission @ 121.5
    High Tx1_enable
    for loop =1 to 30
    DTMFOUT TX_DATA,1000,0,[9]
    gosub checkreedswitch
    next
    Low Tx1_enable ;Stop transmission

    gosub dtmftransmission

    return
    ;************************************************* ******************************
    Blink:
    for loop=0 to 20
    high led
    pause 100
    low led
    pause 100
    next
    return
    '************************************************* ******************************
    'This section is called by the reed switch interrupt

    TurnOffTransmitter:

    gosub blink
    low holdtxon
    End

    '************************************************* *****************************

    ;*********Place Interrupt routines after here********************
    asm
    ReedIntHandler
    ; Save W, STATUS, and PCLATH registers
    movwf wsave
    swapf STATUS, W
    clrf STATUS
    movwf ssave
    movf PCLATH, W
    movwf psave

    ; debounce reed switch .01 seconds @20mhz
    clrf TMR0 ; CLEAR timer 0
    Debounce movlw 0xff ; move 255 into w reg
    subwf TMR0,w ; subtract current count of TMR0 from w
    btfss STATUS,Z ; if status is not zero yet
    goto Debounce ; then continue loop
    bcf INTCON,T0IF ; clear timer0 interrupt flag

    clrf TMR0 ; CLEAR timer 0
    Debounce2 movlw 0xff ; move 255 into w reg
    subwf TMR0,w ; subtract current count of TMR0 from w
    btfss STATUS,Z ; if status is not zero yet
    goto Debounce2 ; then continue loop
    bcf INTCON,T0IF ; clear timer0 interrupt flag

    btfss _ReedSwitchState ; skip next line if the reed switch is high
    goto _TurnOffTransmitter
    bcf INTCON,RAIF ; reset/clear interrupt

    ; Restore PCLATH, STATUS, and W Registers
    movf psave, W
    movwf PCLATH
    swapf ssave, W
    movwf STATUS
    swapf wsave, F
    swapf wsave, W
    retfie ; return and reset GIF
    endasm

  2. #2
    skimask's Avatar
    skimask Guest

    Default Quick glance

    At first glance (and it was a quick one), shouldn't the interrupt subroutines be at the beginning of the program, at the top, in Bank 0 if possible?

    And...right here...

    if reedswitchstate then
    gosub lowvoltagecheck
    else
    pause 1000 ;Wait for a second to make sure the switch
    high holdtxon ;is not being held HIGH
    ----------------------<<<<<<<<<<
    high reedswitchstate
    ----------------------<<<<<<<<<<
    gosub Lowvoltagecheck
    endif

    You're manually holding reedswitchstate (an input pin) with a command for an output pin. Did you actually mean to do something else here? It just doesn't look right to me.

  3. #3
    Join Date
    Dec 2006
    Posts
    9

    Post PIC16F684 Program Question

    The program was copied and pasted twice and thats why the interrupt routine is at the bottom. The interrupt program: ASM to ENDASM is right below the "GOTO Main" title in the real program.
    I was trying to manually change the pin to HIGH to check the logic of the code so that part is not in the actual program. Thanks for looking into this for me. Am going to be working on it some more today and I'll post any progress I make.

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