USART interrpt in PIC16F877A


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  1. #1
    Join Date
    Aug 2006
    Location
    Iran
    Posts
    94

    Default USART interrpt in PIC16F877A

    Hi,
    i have enabled USART interrupt in pic16f877a and it's interrupt work but other part of my program doesn't work.
    im my program i read keyboard and when interrpt is coming it show the recieved data on lcd.
    when serial data is coming the progran goes to interrupt and shoew the recieved data on lcd but reading keyboard doesn't work.
    just the interrupt program is working.when i push the keys the program should show the number on lcd but it doesn't work and when i disable interrupt the keyboard program is working.
    i enabled USART interrup like this:
    on interrupt goto USART_int
    INTCON = %11000000 'Initializing the INTCON register
    PIE1= %00100000 'Initializing the PIE1 register
    RCSTA= %11010011
    and use this instruction :
    serin PORTC.7,N1200,["A"],y1

    could you help me?
    what should i do?
    maby i have a problem in my program.
    i use micro code studio picbasic pro2.41



    this is my program:

    define OSC 4
    include"modedefs.bas"
    ADCON1=7 ' convert porta from analoge to digital
    TRISA = %00000000 ' set porta as an output
    TRISB = %00001111 'set first 4 bit of portb as an input and last 4 bit as putput
    TRISC = %00000000 ' set portc as output
    '----------------------------------------------------
    ' Define LCD parameters
    ' Set LCD Data port
    DEFINE LCD_DREG PORTD
    ' Set starting Data bit (0 or 4) if 4-bit bus
    DEFINE LCD_DBIT 4
    ' Set LCD Register Select port
    DEFINE LCD_RSREG PORTD
    ' Set LCD Register Select bit
    DEFINE LCD_RSBIT 1
    ' Set LCD Enable port
    DEFINE LCD_EREG PORTD
    ' Set LCD Enable bit
    DEFINE LCD_EBIT 0
    ' Set LCD bus size (4 or 8 bits)
    DEFINE LCD_BITS 4
    ' Set number of lines on LCD
    DEFINE LCD_LINES 2
    '----------------------------------------------
    y1 var byte
    y2 var byte
    y3 var byte
    '-------------------------------------------------
    on interrupt goto USART_int
    INTCON = %11000000 'Initializing the INTCON register
    PIE1= %00100000 'Initializing the PIE1 register
    RCSTA= %11010011
    '------------------------------------------------



    scanning keyboard:


    ''program



    goto scanning keyboard

    USART_int:
    disable
    USART_int:
    serin PORTC.7,N1200,["A"],y1
    serin PORTC.7,N1200,["A"],y2
    serin PORTC.7,N1200,["A"],y3
    '
    if (y2=y3) then
    lcdout $fe,1,#y2
    pause 4000
    lcdout $fe,1
    PORTC.4=1
    pause 4000
    PORTC.4=0
    endif
    INTCON = %11000000
    PIE1= %00100000
    RCSTA= %11010011
    resume
    enable
    end
    delay:
    for i=1 to 2000
    pause 1
    next i
    return

    the program that i show you befor is an example but my main prigram is this that it is vey long.
    about my hardware i connected keyboard to PORTB(row to RB0 to RB3 and
    columns RB4 to RB7) and connect the RB0 to RB3 a 10k resister and i set the columns to 1 and read the rows rapidly to find which key is pushed.
    i connected the DS1307 to RA0 and RA1(SDA to RA0 and SCL to RA1).
    my program is about the reviever of a wireless weather station.
    in my program i use haming codes to find and correct errors.
    i connect a RF reciever to PORTC.7 but i my program it is on PORTA.5 that i corrert it in my harware and my software.
    my program is very long abpot 1000 lines that i can't put it here and my keyboard program is long too and it has alot of subrotins.
    what's the difference between serin and hserin instructions?

  2. #2
    Join Date
    Aug 2006
    Location
    Iran
    Posts
    94

    Default

    i found that two interrupts(USART and RB0) are working and when i turn on micro it goes to interrupt routine.
    for RB0 i should connect a pull up resistor but when i connect the out put of the RF reciever to it interrupt occurs.
    i don't know why?
    maby the noise of RF reciever (when we don't have data) is the reason.
    for USART interrupt ,i have the same problem but in this case , there is no deference between connecting and not connecting the RF reciever.
    when i turn on micro it goes to interrupt routine.
    what is the reason?
    what should i do?

  3. #3
    Join Date
    Aug 2006
    Location
    Iran
    Posts
    94

    Default

    Hi,
    i can solve my problem. it works but i have another problem.when i use this interrupt with a simple program it works but when i use this in a big one(my program is about 1000 lines) it doesn't work.
    i also use 20M crystal but it doesn't work too.
    what's the reason?

  4. #4
    Join Date
    Sep 2004
    Location
    montreal, canada
    Posts
    6,898

    Default

    begin small. Have a look there
    http://www.picbasic.co.uk/forum/show...1&postcount=11
    and forget the SERIN stuff. Your PIC have an USART, use it with HSERIN or by reading RCREG
    Steve

    It's not a bug, it's a random feature.
    There's no problem, only learning opportunities.

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