>[snip about change in clock over temperature]
> >
> > As a matter of interest, what range of temperature was this over?

Alex:
>Not much.  Maybe 70 low to 85 high.  Austin, TX.  No real winter here,
>plus I have a bunch of computers.  :-)

That should be fine. I have a design that used a 12C509 (now a 12C672)
and runs quite happily at 9600 baud with the internal RC oscillator.

> > >I though that the internal clock would have been accurate enough for
> > >something as coarse as 1200 baud serial, but apparently it is not.
>
> > Just a note on the baud rate. The accuracy required is not
> > related to the baud rate. 5% at 1200 baud is still the same
> > as 5% at 115200 baud as it's still relative to the chosen
> > baud rate. David...
>
>Hmm.  I guess you are right.  I was getting confused with the receiver.
>If the receiver clock is off, then it should be able to handle 1200 baud
>easier than 115200.

No, it still doesn't matter. The percentage error is no different with the
different baud rates no matter how you look at it. You can probably
tolerate a couple of percent at each end of the link and still be ok.
Maybe like Alan said, the modulation is not really 38KHz although you
can usually be a little off and only suffer reduced range as you start to
get out of the receiver's pass band. See if you can get a look at the IR
or demodulator output on the CRO to check your timing. Heating the
board with a hair drier to see if it wanders.
David...


___________________________________________
David Duffy        Audio Visual Devices P/L
U8, 9-11 Trade St, Cleveland 4163 Australia
Ph: +61 7 38210362   Fax: +61 7 38210281
New Web: www.audiovisualdevices.com.au
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