Beginner having trouble with interrupt..

Hello everyone,
I'm trying to make a simple program that will blink a LED on PortB.2. While waits for an incoming character to PortC.7(with max232). My trouble I think is with the command serin PortC.7, T2400, RX and my PortB.2 doesnt blink. I appreciate any help/guide to understand how I can make this work. :)

Code:

---

CLEAR
include "modedefs.bas" 'include serout defines
DEFINE OSC 20
OPTION_REG=%10000101       
                                ;Bit 7=1 disable pull ups on PORTB
                                ;Bit 5=0 selects timer mode
                                ;Bit 2=1  }
                                ;Bit 1=0  } sets Timer0 pre-scaler to 64
                                ;Bit 0=1  }
                               
INTCON=%10100000        ;Bit 7=1 Enables all unmasked interrupts
                                ;Bit 5=1 Enables Timer0 overflow interrupt
                                ;Bit 2 flag will be set on interrupt and has to be cleared
                                ;in the interrupt routine.  It is set clear to start with.

RX  var byte    ; holds incoming character
symbol led1=PORTB.0
symbol led2=PORTB.1
i    var byte    ;counter
Cnt  var byte
TRISB  = %11110000        ;sets the 3 output pins in the B port
PORTB = %00000000        ;sets all pins low in the B port
TRISC = %10000000  ;Set portC.7 for  serial input                               
ON INTERRUPT GOTO INTERUPTROUTINE       
                       
                               
MAINLOOP:               
        High PORTB.2     
        For i = 0 to 200       
                    Pause 1         
                Next i               
        Low PORTB.2   
        For i = 0 to 200       
                Pause 1 
                Next i
       
  ''''''''''''''''''''''''''''''''''''''''''''''''
    IF Cnt=49 then
            led1=1-led1
            pause 100
            Cnt=0
      endif 

      if Cnt=50 then
            led2=1-led2
            pause 100
            Cnt=0
      endif
GOTO MAINLOOP        ;end of loop
                               
DISABLE       
INTERUPTROUTINE:       
  serin PortC.7, T2400, RX 'Receive menu 
  Cnt = Rx
ENDINTERRUPT:        ;
INTCON.2 = 0                ;clears the interrupt flag.
RESUME                ;resume the main program
ENABLE                ;DISABLE and ENABLE must bracket the int routine
END

---

mbox

Hello mbox,
are you sure your PIC has portC interrupts? Which PIC are you using? I guess my question is what is the source of the interrupt? The timer ? I do not see anything to trigger the interrupt.

Hi joe,
I'm using Pic16F877A, to be honest I'm trying to learn how to use Interrupt command and got stuck...:o

regards,
mbox

With a prescaler of 64 at 20MHz, Timer0 will overflow in about 3.2mS. With your loop from 0 to 200, you're going to have to send a LOT of serial data before it can make it through your loop and toggle PORTB.2 off.

Every 3.2mS it jumps to your SERIN interrupt routine. It's going to sit there until it receives a byte of data. So it's going to take a good while before making it through your first loop.

And, you really don't know what the count in Timer0 is when you exit your interrupt routine, so you might want to clear Timer0 before exiting just in case.

You can check to make sure your Timer0 interrupt is happening by commenting out the SERIN line, and toggling another LED in your interrupt routine.

Something like this;

Code:

---

DISABLE       
INTERUPTROUTINE:       
  'serin PortB.3, T2400, RX 'Receive menu 
  'Cnt = Rx
  TOGGLE PORTB.3
  TMR0=0          ;clear Timer0 before exit
  INTCON.2 = 0  ;clears the interrupt flag.
  RESUME            ;resume the main program
  ENABLE            ;DISABLE and ENABLE must bracket the int routine

---

Hi Bruce,
Thanks for the reply, I realized that when I used the code PortB.3, T2400, RX PortB.2 starts to blink. Is this mean that Portc.7 can not be used as my rx?


thanks in advance,
mbox

Quote:

---

Is this mean that Portc.7 can not be used as my rx?

---

No. I was just pointing out why your original code didn't work as you expected.

It doesn't matter which pin you use for receiving serial data. You just need to understand why your original code isn't working as expected.

Every 3.2mS or so your program jumps to the SERIN interrupt routine. And it just sits there until it receives a byte of data.

This means it will take a very long time before your first loop can finish because it gets interrupted too often for your first loop to complete.

Bruce I adjust the code, but it doesnt blink the led on PortB.1(only high output) When I use the serial communicator and entering 1 (5x) it turns off the led PortB.1. I was expecting that it will trigger PortB.0. :o

Code:

---

CLEAR
include "modedefs.bas" 'include serout defines
DEFINE OSC 20        ;using a 4 MHz oscillator here
TRISC = %10000000
OPTION_REG=%10000101        ;Page 48 or data sheet
                                ;Bit 7=1 disable pull ups on PORTB
                                ;Bit 5=0 selects timer mode
                                ;Bit 2=1  }
                                ;Bit 1=0  } sets Timer0 pre-scaler to 64
                                ;Bit 0=1  }
                               
INTCON=%10100000        ;Bit 7=1 Enables all unmasked interrupts
                                ;Bit 5=1 Enables Timer0 overflow interrupt
                                ;Bit 2 flag will be set on interrupt and has to be cleared
                                ;in the interrupt routine.  It is set clear to start with.
RX var byte ' Receive byte
X    VAR    BYTE        ;Declare x as a variable
i var byte
TEMP      var BYTE 52
Cnt      VAR BYTE 49
symbol led1=PORTB.0
x=20
ALPHA                VAR  WORD        ;this variable counts in the PauseUS loop
BETA                VAR  BYTE        ;this variable counts the 61 interrupt ticks
TRISB  = %11110000        ;sets the 3 output pins in the D port
PORTB = %00000000        ;sets all pins low in the D port
                               
ON INTERRUPT GOTO INTERUPTROUTINE        ;This line needs to be early in the program, before
                                ;the routine is called in any case.
                               
MAINLOOP:               
        High PORTB.1     
        For i = 0 to 10       
                    Pause 1 
                Next i               
        Low PORTB.1   
        For i = 0 to 10       
                Pause 1         
                Next i
       
  ''''''''''''''''''''''''''''''''''''''''''''''''
    IF Cnt=49 then
            led1=1-led1
            pause 100
            cnt=0
    endif 
                 
  ''''''''''''''''''''''''''''''''''''''''''''''''               
GOTO MAINLOOP        ;end of loop
                               
DISABLE       
INTERUPTROUTINE:       
  serin PortC.7, T2400, RX 'Receive menu
  Cnt = Rx
  'TOGGLE PORTB.2
  'TMR0=0          ;clear Timer0 before exit
  INTCON.2 = 0  ;clears the interrupt flag.
  RESUME                ;resume the main program
ENABLE                ;DISABLE and ENABLE must bracket the int routine
END

---

Do I need to change some settings to have my target output?
_____________________
mbox

Try this with Cnt VAR BYTE;

Code:

---

MAINLOOP:               
    High PORTB.1     
    Pauseus 3000 
    Low PORTB.1   
    Pauseus 3000
       
  ''''''''''''''''''''''''''''''''''''''''''''''''
    PORTB.0 = Cnt.0 ' send a 1 or 0 by serial to toggle portb.0
    GOTO MAINLOP

---

ok thanks, i will try it later at home...

__________________
mbox

Hi everyone, I found a program which is the one I'm interested to learn, the code is from mister_e. As I understand I should use PortC.7 as RX. One line to RX and one line to GRND. Using the serial communicator. But it seems I can not trigger led on PortB1. anyone has an idea what I missed? Pls check my connection PC to PIC.
this is the code from mister_e

Code:

---

  '
    '  Simple program to handle USART interrupt using PIC16F877 @20MHZ
    '  ===============================================================
    '
    '  This program will Blink a LED on PORTB.0 to show
    '  that the PIC is running. 
    '
    '  This program also allow the user to activate or deactivate
    '  a LED connected on PORTB.1 pin by sending command from a PC
    '  terminal software using 9600,n,8,1 setting
    '
    '  User command:
    '  =============
    '                1. If character "1" is received => enable the LED
    '                2. if character "2" is received => disable the LED
    '
    '
    'DEFINE LOADER_USED 1        ' using bootloader
    DEFINE OSC 20              ' running at 20 MHZ
   
    '    PORT setting
    '    ============
        '
        TRISC=%10000000        ' RC.7 => USART RX pin set to input
                                ' all other pin set to output
                                '
        TRISB=0                ' RB<7:0> set to output
   
    '    USART setting
    '    =============
        ' Since we will not use HSERIN/HSEROUT, we must
        ' write directly to internal PIC register
        '
        TXSTA=$24              ' enable transmit and SPBRGH=1
        RCSTA=$90              ' Enable USART and continuous receive
        SPBRG=129              ' BAUD RATE = 9600 BAUDS
 
    '    Interrupt definition
    '    ====================
        '
        PIE1.5  =1            ' enable USART receive interrupt
        INTCON.6 =1            ' enable peripheral interrupt
   
    '    Alias definition
    '    ================
        '
        RCIF      var PIR1.5  ' receiver interrupt
        StatusLED var PORTB.0  ' the LED who show a 'running process'
        UserLED  var PORTB.1  ' the LED that user want to control
       
    '    Variable definition
    '    ===================
        '
        Delay    var word    '
        DataIn    var byte    ' use to store RCREG content
        Discard  var byte    ' use to erase RCREG register
       
    '    Hardware/software initialisation
    '    ================================
        '
        PORTB=0                ' clear PORTB       
        on interrupt goto USARTInterrupt
       
Start:
    '    Main program loop that make the user happy to
    '    see a LED flashing to mean that something is
    '    running
    '
    toggle statusled
    for delay = 1 to 5000      ' use a loop delay to ensure
      pauseus 5                ' getting interrupt as fast as
      next                      ' possible
    goto start
   

disable interrupt
USARTInterrupt:
    '    Here's the interrupt routine who will make the user
    '    much happy by giving him the feeling to have the
    '    control on the machine when the status of the user
    '    LED will change
    '
    RCSTA=0                    ' Disable serial port AND
                                ' clear possible error (FERR,OERR)
                               
    datain=RCREG                ' Get data
                               
    while RCif                  ' wait untill the RCREG is empty
          discard=RCREG        ' by reading it and store result in a
    wend                        ' don't care variable
                               
    select case datain          ' What to do with that data???
                               
          case "1"            ' User selection = 1
                userled=1      '      => Enable the LED
                               
          case "2"            ' User selection =2
                userled=0      '      => disable the LED
                               
          end select         
    RCSTA=$90                  ' Re-enable the serial PORT AND
    resume                      ' get out of here
enable interrupt

---

thanks,
mbox

Here, READ THIS, and UNDERSTAND IT.( the link that is)
You are using code from mister_e. mister_e writes good code, so what are you doing or not doing correctly? Right off the top I see there are no config statements, and the OSC is defined at 20 mhz, guess what? The DEFAULT config statement in the 16F87x.inc file (actual number may vary) is set for XT_OSC which means it will provide only enough power to swing 4 mhz, you need HS_OSC to run at 20 mhz.
http://www.picbasic.co.uk/forum/show...3375#post73375
If no OSC then no blinky.