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FAM
04-28-2007, 06:21 AM
My BS1 application, on a BS1 project board, is working fine, but the
computer used to program it needs to be at the other end of a 60 ft
CAT 3 run. The Stamp editor doesn't seem to be able to recognize
the BS1 when simply wired straight through, although a breakout
box shows the protocol is working - after seeing ATN, the BS1
does respond. i don't have a 'scope so there's no way to look at
the signals directly.

Perhaps the voltage produced by the serial interface is marginal,
or maybe 60 ft or so of CAT 3 damages the signal too much. Ideally I
would like to only use 2 pairs, which precludes using a short haul
modem if the BS1 protocol is full duplex.

Much searching and Googling hasn't helped, hence this post. Here
are the questions (please point me at the fine manual page if I missed
something http://forums.parallax.com/images/smilies/smile.gif

It would help if I know exactly what signals and signal levels are available
at the DB9 connector. Is this information available?

Is there any consensus that this should work? 50ft or so doesn't
seem particularly long at only 4800bps. Would using a voltage
shifter make this work?

Is the programming protocol full duplex? If not, is there some
signal that can be used to toggle a half duplex solution? (this would
be needed at both ends.)

Any insights would be much appreciated. I have another project,
using a BS2, which will also be at the far end of the same CAT3
cable, so it will probably have the same problem...

Thanks

FAM
05-01-2007, 08:18 AM
Replying to my own post, just in case anyone else wants to program
a STAMP remotely, it works just fine over two pairs of 60ft CAT 3
cable http://forums.parallax.com/images/smilies/smile.gif

The trick is not to use a patch cord which does a crossover :-( as
most RJ11 patch cords do as it turns out)

Evidently the BS1 responds quite happily to the TX signal when
connected to the ATN pin on the DB9, so it looks like it is working
when you look at the LEDS on a breakout box.

I wonder if it would work over even greater distances? Note that
CAT5 wouldn't buy anything because the RS232 signal is unbalanced.

Attached is a schematic for a simple level shifter that can be made
out of parts you might have lying around. It turned out I didn't
need it, but maybe it might come in useful for someone...