Serial Communication Problem

[mister_e]

Here's something to play with.

    '   Program to echo incoming serial data 
    '   Baudrate : 2400 Bauds
    '   Method :   Polling USART interrupts flags

    '   Pic Definition
    '   ==============
        ' Using PIC 18F2320 @ 4MHZ and bootloader
        '
        DEFINE LOADER_USED 1
        DEFINE OSC 4
        
    '   Hardware configuration
    '   ======================
        '
        '
        TRISC  = %10000000    ' PORTC.7 is the RX input
                              ' PORTC.6 is the TX output
    
    '   Serial communication definition
    '   ===============================
        ' Using internal USART and MAX232 to interface to PC
        '
        RCSTA = $90 ' enable serial port, 
                    ' enable continuous receive
                    '
        TXSTA = $24 ' enable transmit, 
                    ' BRGH=1
                    '
        SPBRG = 103 ' set baudrate to 2400                   
        
    '   Alias definition
    '   ================
        '
        '
        RCIF VAR PIR1.5     ' Receive  interrupt flag (1=full , 0=empty)
        TXIF VAR PIR1.4     ' Transmit interrupt flag (1=empty, 0=full)
        OERR var RCSTA.1    ' Overrun error
        CREN var RCSTA.4    ' Continuous receive
                
    '   Hardware initialisation
    '   =======================
        '
        '
        pause 10 ' safe start-up delay
    
Main:
    if oerr then  ' Overrun error?
       cren=0     ' clear it
       cren=1
       endif

    if RCIF then    ' incomming data?
       TXREG=RCREG  ' take it, send it
       while TXIF=0 ' wait untill transmit buffer is empty
       wend
       endif
    goto main

the following use HSERIN/HSEROUT statement. Since your PIC have internal USART... why not using it

    '   Program to echo incoming serial data 
    '   Baudrate : 2400 Bauds
    '   Method :   Polling USART interrupts flags

    '   Pic Definition
    '   ==============
        ' Using PIC 18F2320 @ 4MHZ and bootloader
        '
        DEFINE LOADER_USED 1
        DEFINE OSC 4
        
    '   Hardware configuration
    '   ======================
        '
        '
        TRISC  = %10000000    ' PORTC.7 is the RX input
                              ' PORTC.6 is the TX output
    
    '   Serial communication definition
    '   ===============================
        ' Using internal USART and MAX232 to interface to PC
        '
        DEFINE HSER_RCSTA 90h ' enable serial port, 
                              ' enable continuous receive
                              '
        define HSER_TXSTA 24h ' enable transmit, 
                              ' BRGH=1
                              '
        define HSER_SPBRG 103 ' set baudrate to 2400                   
        DEFINE HSER_CLOERR  1 ' automatic clear overrun error  
        
    '   Alias definition
    '   ================
        '
        '
        RCIF VAR PIR1.5     ' Receive  interrupt flag (1=full , 0=empty)
        TXIF VAR PIR1.4     ' Transmit interrupt flag (1=empty, 0=full)
        
    '   Variable definition
    '   ===================
        '
        '
        SerialData var byte
        
    '   Hardware initialisation
    '   =======================
        '
        '
        pause 10 ' safe start-up delay
    
Main:
    if RCIF then            ' incomming data?
       hserin  [Serialdata] ' take it
       hserout [serialdata] ' send it
       endif
    goto main

hope this help