[time-nuts] Rapco 1804M - serial problems?
David J Taylor
david-taylor at blueyonder.co.uk
Tue Oct 18 06:49:41 UTC 2011
> Do you have a scope?
> I'd check the voltage levels, the bit timing, and the rise/fall times.
> can also check the timing on the receiving system by getting it to send
> Sometimes the UART uses a handy clock that doesn't generate exact
> frequencies. Usually that's only a problem at faster baud rates.
> If the driver is weak, the rise time might be a problem. (But 4800 is
> If that all looks good, I'd expect there is some sort of noise. How
> long is
> the run? How close are the grounds? Try disconnecting the DB-9 at the
> receiver and putting the scope on the ground pin.
Many thanks for your suggestions, Hal. I've been through most of them,
levels are good +/- 7 V), timing is good, rate is within a couple of Hz of
4800, noise is non-existent, it's all close together (2-3 m). The same
RS-232 port talks correctly to a Garmin 12 XL and an Icom R8500. So,
remarkable as it is, it seems that either the serial chip is bad, or bad
data is being sent to the chip.
(With all the things to set - baud rate, male/female, 9/25-pin,
terminal/computer, hard/soft/no handshake, parity. stop bits - it reminds
of how easy USB or network connections have now become! At least they
SatSignal software - quality software written to your requirements
Email: david-taylor at blueyonder.co.uk
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