PIC micro uart puzzle

[Randy Day]

Can anyone suggest why the following is happening?

I have two Pics, a '690 and a '2455, communicating
via eusart (8-bit). After a succesful round of
query/response, the '690 transmits (confirmed on
scope), but the '2455 doesn't receive.

'690 '2455
---- -----
. MOVWF TXREG
BTFSS PIR1, RCIF .
GOTO $-1 .
MOVWF TXREG BTFSS PIR1, RCIF
. GOTO $-2

; things work well up to here.
; successful comm is displayed

. BTFSS PIR1, RCIF
. GOTO $-2

; a delay, up to several seconds, occurs

MOVWF TXREG .

; and here the 690 xmits, but the 2455
; stays in the loop...

I could see a config problem if there was no comm
at all, but why work and then stop? All
suggestions gratefully accepted.

 

[George Jefferson]

"Randy Day" <randy.day@sasktel.netx> wrote in message
news:MPG.266e08a1478ae4059896b9@news.sasktel.net...

Can anyone suggest why the following is happening?

I have two Pics, a '690 and a '2455, communicating
via eusart (8-bit). After a succesful round of
query/response, the '690 transmits (confirmed on
scope), but the '2455 doesn't receive.

'690 '2455
---- -----
. MOVWF TXREG
BTFSS PIR1, RCIF .
GOTO $-1 .
MOVWF TXREG BTFSS PIR1, RCIF
. GOTO $-2

; things work well up to here.
; successful comm is displayed

. BTFSS PIR1, RCIF
. GOTO $-2

; a delay, up to several seconds, occurs

MOVWF TXREG .

; and here the 690 xmits, but the 2455
; stays in the loop...

I could see a config problem if there was no comm
at all, but why work and then stop? All
suggestions gratefully accepted.

Clear the recieve buffer? It may be full and hence it can't recieve any more
messages until cleared.

Does it depend on the specific msg type? Try various messages or all
messages and see if any get through. If some get through then probably a
config problem.

Not sure on the pic16's but your recieve buffer may not be configed
properly.

The clocks may be out of sync causing some problems.

Check the errata as I recall some issues with the uart module.

 

[petrus bitbyter]

"Randy Day" <randy.day@sasktel.netx> schreef in bericht
news:MPG.266e08a1478ae4059896b9@news.sasktel.net...

Can anyone suggest why the following is happening?

I have two Pics, a '690 and a '2455, communicating
via eusart (8-bit). After a succesful round of
query/response, the '690 transmits (confirmed on
scope), but the '2455 doesn't receive.

'690 '2455
---- -----
. MOVWF TXREG
BTFSS PIR1, RCIF .
GOTO $-1 .
MOVWF TXREG BTFSS PIR1, RCIF
. GOTO $-2

; things work well up to here.
; successful comm is displayed

. BTFSS PIR1, RCIF
. GOTO $-2

; a delay, up to several seconds, occurs

MOVWF TXREG .

; and here the 690 xmits, but the 2455
; stays in the loop...

I could see a config problem if there was no comm
at all, but why work and then stop? All
suggestions gratefully accepted.

Having ome experience with PICs I guess you have to reset some flag (PIR1
maybe?) after reading the received data otherwise the UART does not accept
new data. Beware. Small differences may cause big problems. You'll have to
check the datasheet of the 2455 including the errata to hope to be sure to
have 100% reliable data.

petrus bitbyter