Maybe this will help. It may not be the most efficient routine but it works
If you have 2 ASCII bytes '2' (0x32) and '3' (0x33) call the Asc2Hex
routine with the
register Tmp containing 0x33 and Tmp+1 containing 0x32. When the routine
finishes the WREG will contain 0x23. You may need to nodify this to filter
your junk charachters. If you do maybe you would be kind enough to send me
a copy. It was'nt an issue for me when I wrote this. The code was written
for a 17c44 but should be easily ported for other stuff


Asc2Hex
        movlw   0x40            ;Check data for A to F
        cpfsgt  Tmp
        goto    NumLo
AlphaLo movlw   0x37
        subwf   Tmp,WREG
        goto    SaveLo
NumLo   movlw   0x30            ;Check data for 0 to 9
        subwf   Tmp,W
SaveLo  andlw   0xf             ;Save in the lo nibble of the reg
        movwf   Tmp
        movlw   0x40            ;Check data for A to F
        cpfsgt  Tmp+1
        goto    NumHi
AlphaHi movlw   0x37
        subwf   Tmp+1,WREG
        goto    SaveHi
NumHi   movlw   0x30            ;Check data for 0 to 9
        subwf   Tmp+1,W
SaveHi  andlw   0xf             ;Save in the hi nibble of the reg
        swapf   WREG
        addwf   Tmp,WREG
        return


The Hex2Asc routine does the opposite You call it twice for each byte you
want to convert to it's ASCII representation as follows

        movfp   INDF1,WREG             ;Byte to be converted is pointed to by IN
DF1
        movwf   Tmp                     ;Move byte to be converted to Tmp
        movlw   0xf0                    ;Convert high nibble
        andwf   Tmp
        swapf   Tmp
        call    Hex2Asc
        movfp   INDF1,WREG
        movwf   Tmp                     ;Move byte to be converted to Tmp
        movlw   0x0f                    ;Convert high nibble
        andwf   Tmp
        swapf   Tmp
        call    Hex2Asc

Hex2Asc                     ;A nibble of the byte to convert is in Tmp
        bcf     Carry
        movlw   9
        subwf   Tmp,WREG
        btfss   Zero
        btfss   Carry
        goto    ZNumHi
        bcf     Carry
        movlw   37
        addwf   Tmp
        movfp   Tmp,WREG
        return
ZNumHi  movlw   30
        addwf   Tmp
        movfp   Tmp,WREG           ;ASCII byte is in WREG
        return



At 14:51 28/05/99 -0700, you wrote:
>Does anyone have a nice code snippet that takes a byte containing a hex
>character (0x30 through 0x39 and 0x41 through 0x46) and converting it to a
>plain numeric byte, 0x00 through 0x0F? Everything that comes to mind seems
>wasteful and clunky.
>
>The character coming in may also contain junk that must be filtered out.
>
>Thanks!
>
>Happy long weekend if you get one. Cheers,
>Bob
>
>