PIC18F4550 USART problems.

[Vizier87]

Hello guys,

I've been using PIC18F4550 which is connected to a PC via RS232 with a USART 8-bit configuration. For transmission of 8-bit data with a baud rate of 2400 bps is good, but I've been having problems in receiving data from a PC because the programming keep polling the RCIF where when data is received, RCIF=1, but the problem is that RCIF never gets to be 1.

Here is the code:

Main:
setf count
clrf TRISB
movlw b'10000000'
movwf TRISC
movlw 0x00
movwf TRISD

;initialize uart
movlw b'01001010'
movwf BAUDCON
movlw 0x22
movwf SPBRG
movlw 0x08
movwf SPBRGH
;2400 baudrate

bcf TXSTA , SYNC
bsf RCSTA , SPEN
bsf RCSTA , CREN
loop btfss PIR1 , RCIF 
     goto $-1
btfsc RCSTA , FERR
goto  clearf
btfsc RCSTA , OERR
goto  clearo
movf  RCREG , W
movwf PORTB
;clrf PORTB
goto loop

clearf bcf RCSTA , CREN ; clear framming error
	bsf PORTB , 7	   
       goto loop

clearo bcf RCSTA , CREN ; clear overrun error
        bsf PORTB , 6
	goto loop

Sometimes the data received is not accurate.
Please give some advice.
Thanks.

 

[Vizier87]

Anything else I should add for the details?

 

[Wp100]

Hi,

You are using a 18F chip, so $-1 does not work as it would on a 16F chip, as the 18F instructions are in 2 or 4 bytes, so you must use $-2.

Using a Goto avoids any such migration problems.

 

[Vizier87]

Thanks, I'll look into it.

 

[Pommie]

Looks like Wp100 found your problem. Just change goto $-1 to goto loop.

Mike.

 

[Vizier87]

Thanks Mike, good to have a reassurance.

 

[Vizier87]

the change is made, but still I experience the same problem. Anything else which might be amiss?