On 22/11/2010 13:12, Olin Lathrop wrote:
> Oli Glaser wrote:
>>> If I really needed to know what a A/D reading was in this setup as a
>>> one-off, I would probably use two pins, one clock and one data.  A
>>> sequence of 10 clocked bits is short enough to be captured on a
>>> scope and then analysed by hand.  It's only 10 bits after all.
>> Yes, that's the kind of thing I was thinking of when I mentioned bit
>> banging stuff - a couple of pins, or maybe just one Tx pin if they are
>> in short supply, then you could use the PicKit2 UART tool. I have done
>> this quite a lot - I just use the PGC/PGD pins as the Tx/Rx so it
>> saves having to move the PicKit2 connections at all.
> Yes, you could do it with one pin and a UART to receive bytes.  The probl=
em
> with that is that the timing has to be just right.  While that's doable,
> it's a lot more work than just clocking out 10 bits and analyzing the sco=
pe
> capture once or twice.  If you had to do it regularly, then the extra eff=
ort
> of creating a software UART at a standard baud rate could be worth it.
>

Maybe in this case to read one or two registers it's not so important,=20
but I find it helps for reading a bunch of data out. I have a few=20
standard C routines in a file I wrote ages ago that I add to my project,=20
set the baud rate and it's ready - timing is not a big deal really as=20
it's unlikely you need to send the data quickly, I usually use 4800 or=20
9600. I just used this for debugging the Temp Logger project I as=20
working on, quite useful for reading the various registers of the Dallas=20
sensors, RTC and the values written to eeprom.
The PicKit2 UART tool is the main reason I do it like this, as it uses=20
the same lines for the UART as programming.
I'm sure people all have their favourite methods of debugging small=20
micros - I like the Morse code beeper just mentioned... :-)


--=20
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