20 Aug
2011
20 Aug
'11
11:04 a.m.
[RS232]
Ignore the standard, and leave the break-out box in
the drawer.
After years of practically memorizing the (horrible) standard and trying
to do things "by the book" analytically, etc, I refer to it as "RS-232
in-your-face" rather than "interface".
It's odd... I would give the opposite advice. Since I started using a
breakout box (or similar) to see just what the devices were doing I find
I can wirte a serial cable and get it to work first time (at least most
of the time :-)).
First test is to connectr a breakout box or a quick-checker (one of thos
adapters with LEDs montiros i nthe most important signals) to each device
in turn That will tell me which signals it's driving, and henxe if it's
a DTE (driving pin 2 at least) or a DCE (driving pin 3). From whihc
handshake lines are driven you can make a fair guess as to which
handshake inputs it'll be listening too (if it drives RTS, it may well be
looking at CTS, etc). If in doubt, I trace the pins inside to th buffer
chips (takes a few minuts at most).
Then I patch up a cable to link ground (pin 7) and the data lines (2,3)
appropriately. Try that. If one device won't sent anything, I try
asserting handshake lines until it dosn
Everything I use with an RS23 connector other than a DB25 (I have machines
with DE9s (assorted wring!),Qunicuncial 5 pin DIN plugs (3 diffferent sets
of conenctions), 8 pin DIN, 8 pin mini-DIN, 50 pin microribbon, 4 pin
header plugs, 10 pin headre plugs, etc) gets a cable to convert it to a
DB25 of the appropriate gender.
-tony