source= http://www.piclist.com/piclist/2003/08/18/221918a.txt?



>PICers - any advice on this one would be most appreciated. 'Tis my 1st foray
>into RS232 - i have this old KODAK DC50 dig cam that takes 9600 bd, 8E1. I'm
>doing this one coz Oliver Hartmann has/had(?) a handy page about it so i
>figured it'd be easy .....  yeah, right :(
>
>OK, I got the cam sorta detecting the fact it's being spoken to but NO WAY can
>I get the damn thing to take a picture. I reckon the prob might in the TX
>routine as I'm not real clear about whether u should treat stop bits as active
>low in RS232 or not. Parity i understand (I think) so that part should be OK?
>
>I'm generating RS232 sigs from a PIC using a MAX232.
>
>If anyone could offer advice/spot anything that don't look right ... heh, well
>thankz! i'm totally stumped right now :(
>
>Debbie  :)
>
>

Snip

I have not looked at the rest of the code but what you have below is wrong.

Your BITWAIT MACRO delay period is 3uS ( @ 4MHz ) per count
(except for the last count which is 2uS)

So, doing the math

0x32 = 50 DEC

50 * 0.000003 = .00015 = 150uS  (not 104uS)

You actually need to use  35 DEC  (0x23) for your Bit delay

34 * 3 = 102  plus 2 for the last cycle = 104uS

You can subtract a little for overhead but it really is not going to
matter for a 9600 Baud link.

BTW. Bob suggested it might be LANC. (I  also suggested as much a month or
so ago.)

LANC is easy to spot as it is a 8-byte packet protocol. If your camera is
LANC (A.K.A. Control -L) then a MAX232 chip is no good as the
RS232 needs a Open collector output.

If you thing it is LANC, I can email all the data I have. Let me know.


Regards,

Jim Robertson
NEWFOUND ELECTRONICS



>;***************************************************************************
>;BITWAIT  .. used in serial tx routines with the DC50. Waits for
>;            1 bit period. For 9600 baud, BITWAIT should be 104.2 usec
>;For a 4MHz Xtal, BITWAIT count = $32 gives 104 uS in a single loop counter?
>;***************************************************************************
>BITWAIT  MACRO                  ;Wait for the duration of one Bit
>          IFDEF DEBUG
>            nop                  ;Inactive in DEBUG mode
>          ELSE
>           movlw    0x032        ;Calculate C1= 0x033 for 4.0MHz Xtal.
>           movwf    count_02
>           decfsz   count_02,1
>            goto    $-1
>           ENDIF
>          ENDM
>



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