I don't see a "BSF RCSTA, CREN" anywhere in your code, I think you need
one.

Cheers,

Bob


On Wed, 15 Apr 2009 15:04:27 -0500, "Tom Cassidy" <tomc@featherstep.com>
said:
> All,
> 
> I cannot get the receiver portion of a PIC16F690 EUSART to work.  I can 
> transmit fine, but am unable to receive characters.
> 
> Since I can transmit, I'm assuming my baud rate generator settings are 
> correct.
> 
> I have checked the signal at the RX pin and it is good- correct 
> polarity, correct baud rate, correct voltage level.  I can see the RS232 
> signals arriving when sent from the PC.  They compare exactly to those 
> from the TX pin when the PIC is sending the same character.
> 
> I tried using source code from your "PIC Specific RS232 IO" page by 
> MaGahee et al. to no avail.  (Love the code and comments btw- well done!)
> 
> I tried using rs232.asm from Mark Torrens, also to no avail.
> 
> I have a test board with only the PIC16F690 and a 3.6864MHz clock chip, 
> so nothing else should be interfering, hardware-wise.  I also built out 
> two of the boards, so it probably isn't a fab issue.  (I've got an 
> external RS232 to TTL converter.)
> 
> At one point I noticed that the FERR bit always seemed to get set, even 
> if I cleared the queue and no characters were being sent to the PIC.  I 
> never saw OERR asserted, only the FERR signal.
> 
> Any suggestions or help would be greatly appreciated- I've already 
> wasted two days on this!
> 
> Thanks,
> Tom
> 
> p.s. Here's my setup code:
>    __CONFIG     _FCMEN_OFF & _IESO_OFF & _BOR_OFF & _CPD_OFF & _CP_OFF & 
> _MCLRE_ON & _PWRTE_ON & _WDT_OFF & _EC_OSC
> 
>    BANKSEL         ANSEL
>    CLRF            ANSEL                  ; Digital I/O
>    CLRF            ANSELH                 ; Digital I/O
> 
>    BANKSEL            TXSTA                    ; Select bank 1
>    CLRF             TXSTA
>    BCF                TXSTA, TX9               ; Select 8-bit
>    transmission
>    BCF                TXSTA, TXEN               ; Disable transmission 
> initially
>    BCF                TXSTA, SYNC               ; Asynchronous mode
> ;    BSF                TXSTA, BRGH               ; High baud rate
>    BCF                TXSTA, BRGH               ; low baud rate since 
> using extrnal 3.6864MHz clock.
>      BANKSEL         SPBRG
>    MOVLW            D'5'                  ; Baud rate counter value
>    MOVWF            SPBRG                  ; for 9600 baud, 3.6864MHz
>    clock
> 
>    BANKSEL         TXSTA
>    BSF                TXSTA, TXEN            ; Enable transmission
>      BANKSEL             RCSTA          BSF                RCSTA, 
> SPEN            ; Enable serial port
> 
>    movlw    'B'
>    btfss    PIR1,TXIF
>    goto    $-1
>    movwf    TXREG                ; send character- this works
> 
> 
> 
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