> Hi all,
> still battling with this serial coms.
>
> Question: do I have to use a proper xtal (metal can type) for accurate
> timing for serial communication, or is a ceramic resonator adequate?

Ceramic resonators should be accurate and stable enough. You can
have a timing error of several % before you will see any problems.

On the other subject of Rxing data, you would use a pullup resistor
to Vcc if for example the data output from the basic stamp was an
open collector or open drain output (I have no idea if it is). As your
logic probe seems to indicate there is data present you might
assume you are getting a good voltage swing (0 - 5V ideally) so you
can feed it straight into the PIC.

If you watch the data output from the stamp, or the TxD output of
the PIC, you should see that it sits idle at +5V while not transmitting
anything. The first falling edge is the beginning of the start bit,
followed by the data, then the last low pulse is the stop bit, returning
high to the idle state.

Brent Brown
Electronic Design Solutions
16 English Street
Hamilton, New Zealand
Ph/fax: +64 7 849 0069
Mobile/text: 025 334 069
eMail:  brent.brown@clear.net.nz

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