IVP <joecolquitt <at> clear.net.nz> writes:

>=20
> > The baud rate accuracy requirement increases with baud rate
>=20
> Error percentage is constant, whatever the speed. The only way
> to do serial with any confidence when the clock is liable to drift
> would be to use bit-banging, timing based on a bit length of the
> external transmitter. Not as convenient as the PIC's serial module
> but it can be done fairly easily

This can be done with auto baud rate detection in some of the PICs.  I beli=
eve
PIC24 have it.  In this case, sender will send 1 byte to sync the clocks, w=
hile
receiver is in the auto baud detection mode.  I have a test setup that does=
 this
with PIC24FJ32GA002 and an internal RC oscillator.  Works fine even with ma=
in
clock frequency variation as high as 4x ( +/- PLL).  The auto baud sync can=
 be
done before each packet of information.  In this case, even crappy RC clock=
 is
stable over short, ~10-100 ms, time.=20

Sergey Dryga

http://beaglerobotics.com




--=20
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