Can you still get those LED adapters? At one time
just about every PC
shop sold them, but now, since RS232 is out of fashion, I've nto seen
them on sale for several years.
PC shops sell new PCs and games, that's about it. The world's
'Twas always the way. I very rarely go to such places since they're
unlikely to have anything I want. Even when my PC wasn't _quite_ os
old-fashioned, they enver had the cable or wahtever that I wanted...
I can rememebr one time I visitied such a palce, they had a few shelves
for 'operating systems'. All that was there was the installation and
upgrade kits for Windows. They sold Linux, but classed it as a 'book'
(!). Hmmm...
marketplace has moved to eBay. You can get them
(brand new of
course...a lot of people think something is "used" or "old" if the
sales
venue is eBay) all day long, cheap, on eBay.
OK...
It's not hard to make one, but...
...but a complete waste of time, unless you've got nothing better to do.
Well ,that depends... It's not a waste of time if they;re no logner
avaialble. And the one I got was unrleiable from new due to an excessive
numebr of dry joints inside. I resoldered the lot and it's been fine for
getting on for 20 years. Resodlering one probably takes less time than
making one, but...
The other
trikc is to see what flow control lines are being driven, and
it noting works, to try loppign them back to what they normally pair with
(e.g. if pin 4 -- RTS -- is being driven by a device and you can't get it
to sand anything, try connecting RTS to CTS (4 to 5)). You migth end up
with a thing that drops data due to buffer overrun from time to time, but
you sort that out once you've got it sending something.
I literally cannot remember the last time I had to do anything with
other than 2, 3, and 7. Even one of the controller designs I inherited
I can. It was a couple of months back. I'd bought and then repaired a
piece of test gear [1] which had a helpfully-labelled 'RS232 (DTE)'
connector on the back. And it was clear from the setup options on the
display how to make it use the RS232 port rather than the GPIB prot, and
how to set the baud rate. So I did, and found it would send nothing.
Strapping the handshake lines back got it to output a prompt to the
terminal. Alas I've not got any further, I can't figure out what commands
to send.
[1] A rather nice telephone line simulator. We talked about those here
soem time back as a device for woriking with and testing old modems. I
decided I wanted somthing I could use for this and came up wit ha sort-of
design. I then foudn there were 3 options, all of which would cost aobut
the same :
Make the design I'd come up with and debug it
Buy a cheap, new device for the purpose, which wouldn't do anything more
and would probably be hard to repair if it failed
Buy a non-working professional line simulator and repair it.
On the grounds the last would provide me with the best device in the end,
I went that route. If I'd not been able to repair it, I'd guessed that
many of the bits in it would be useful for my homebrew idea. As it
happened, it took me quite some time to find the fault and then a few
pence worth of parts (a couple of LM311s and an LM337) and a few minutes
to fix it. Well, there are 6 microprocessors and a total of over 200 ICs
spred over 10 PCBs in the darn thing ;-)
-tony
