>
>
>> so to test it I have a 5K pot connected between 5V and ground
>
>The maximum recommended pot is 2k5 for the 18F452, not 10k
>as on previous families. I can't say if anything else is wrong
>with your set-up but you should correct this first
>

A 5k pot gives a 1.25k source impedance, so this is well in spec.  A 10K
pot
would be just in spec at 2.5K.

Mark, could the you post the code you are using to perform the
conversion
and read the A/D result?  Is your PIC well decoupled with suitable
capacitors physically near the Vss and Vdd pins?

Hi Mike
Thanks for the reply
The board I made has the pic interfaced to a FTDI USB chip and I have
routines to send to and receive from the board and a VB6 program on my
pc to send commands and receive info and do the GUI. Both chips have a
0.1uF and 10uF tant decoupling. The whole board uses smd components with
the caps within mm of the chips.
The simple routine I use for doing the conversion is as follows:

do_b    =09
                        bsf     ADCON0,GO,0             ; Start  A/D
conversion
adconvtst               btfsc   ADCON0,DONE,0   ;Is conversion complete
                        goto    adconvtst               ;No, go test
again
                =09
                        movf    ADRESH,w,0              ;get high byte
                        call    sendbyte                ;send it to USB=20
                        movf    ADRESL,w,0              ;get low byte
                        call    sendbyte                ;send it to USB

                        goto    again                   ;back to read
USB for command loop




NOTE: This e-mail message is subject to the MTN Group disclaimer see http:/=
/www.mtn.co.za/email_disclaimer.asp

--
http://www.piclist.com#nomail Going offline? Don't AutoReply us!
email listserv@mitvma.mit.edu with SET PICList DIGEST in the body