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**Nigel Goodwin** · 20th June 2007, 02:53 PM

Are you sure the polarity of the data was correct?, remember the MAX232 inverts it - and are you sure the baud rate was set correctly?. Both of these will give weird characters.

emufambirwi · 21st June 2007, 06:59 AM

Yes, the baud rate was set correctly as follows in software.

TXBYTE MOVWF BYTE ;save table value to BYTE
MOVLW 0x08
MOVWF BITCNT ;do eight times
BCF TXPIN ;SEND START BIT
CALL Bit_Delay ;delay 104 instruction cycles
;assuming 4MHz clock, that's 1us per instruction cycle
;so delaying 104us
TXLOOP RRF BYTE,F ;move BYTE bit0 into carry
BTFSS STATUS, C ;a Low ?
BCF TXPIN ;yes, send it
BTFSC STATUS, C ;a High?
BSF TXPIN ;yes, send it
CALL Bit_Delay
DECFSZ BITCNT
GOTO TXLOOP ;loop for 7 more times
BSF TXPIN ;SEND STOP BIT
CALL Bit_Delay
RETURN

emufambirwi · 21st June 2007, 07:04 AM

sorry about the above post, the 104us delay is generated as follows, I have simulated the program using mplab and the timing is correct.
Bit_Delay
MOVLW 0x21
MOVWF DELAYCNT

DELAYLOOP
DECFSZ DELAYCNT ;one cycle if DELAYCNT
GOTO DELAYLOOP ;two cycles
RETURN

emufambirwi · 21st June 2007, 07:23 AM

My code snippets are not coming out clearly, what do I do?

**Nigel Goodwin** · 21st June 2007, 08:05 AM

Quote:

Originally Posted by emufambirwi

My code snippets are not coming out clearly, what do I do?

Surround them with the 'Code' tags, click on the 'Advanced' button where it's an option.

emufambirwi · 21st June 2007, 08:21 AM

I did not receive a comment on my delay, is it ok

**Nigel Goodwin** · 21st June 2007, 08:35 AM

Quote:

Originally Posted by emufambirwi

I did not receive a comment on my delay, is it ok

I didn't check it, just use the one from my tutorial which is known to work (uses a 4MHz clock).

emufambirwi · 21st June 2007, 12:21 PM

Quote:

Originally Posted by Nigel Goodwin

Are you sure the polarity of the data was correct?, remember the MAX232 inverts it

How do I invert the data again in software?

**Nigel Goodwin** · 21st June 2007, 01:50 PM

Quote:

Originally Posted by emufambirwi

How do I invert the data again in software?

Switch the BCF's and BSF's in the transmit routine - don't forget the start and stop bits as well.

emufambirwi · 22nd June 2007, 09:47 AM

ok thanks, feedback later

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20th June 2007, 02:53 PM	(permalink)
Nigel Goodwin	Are you sure the polarity of the data was correct?, remember the MAX232 inverts it - and are you sure the baud rate was set correctly?. Both of these will give weird characters. __________________ PIC programmer software, and PIC Tutorials at: http://www.winpicprog.co.uk

21st June 2007, 06:59 AM	(permalink)
emufambirwi	Yes, the baud rate was set correctly as follows in software. TXBYTE MOVWF BYTE ;save table value to BYTE MOVLW 0x08 MOVWF BITCNT ;do eight times BCF TXPIN ;SEND START BIT CALL Bit_Delay ;delay 104 instruction cycles ;assuming 4MHz clock, that's 1us per instruction cycle ;so delaying 104us TXLOOP RRF BYTE,F ;move BYTE bit0 into carry BTFSS STATUS, C ;a Low ? BCF TXPIN ;yes, send it BTFSC STATUS, C ;a High? BSF TXPIN ;yes, send it CALL Bit_Delay DECFSZ BITCNT GOTO TXLOOP ;loop for 7 more times BSF TXPIN ;SEND STOP BIT CALL Bit_Delay RETURN __________________ People perish because of lack of knowledge

21st June 2007, 07:04 AM	(permalink)
emufambirwi	sorry about the above post, the 104us delay is generated as follows, I have simulated the program using mplab and the timing is correct. Bit_Delay MOVLW 0x21 MOVWF DELAYCNT DELAYLOOP DECFSZ DELAYCNT ;one cycle if DELAYCNT GOTO DELAYLOOP ;two cycles RETURN __________________ People perish because of lack of knowledge

21st June 2007, 07:23 AM	(permalink)
emufambirwi	My code snippets are not coming out clearly, what do I do? __________________ People perish because of lack of knowledge

21st June 2007, 08:21 AM	(permalink)
emufambirwi	I did not receive a comment on my delay, is it ok __________________ People perish because of lack of knowledge

22nd June 2007, 09:47 AM	(permalink)
emufambirwi	ok thanks, feedback later __________________ People perish because of lack of knowledge