Looking for dialup hardware solution

[phiscock-g851W1bGYuGnS0EtXVNi6w at public.gmane.org]

>> For what it's worth, we found that USB-Serial control includes hardware
>> flow control (RTS-CTS handshaking).
>>
> Good to know. It's just that I have too many recollections of the
> nightmares I had with breakout boxes trying to make various kinds of
> modems work with various kinds of serial ports. If only hardware
> handshaking was always just RTS/CTS. :-)
>
> (On a DB9 cable things weren't that bad, there weren't too many ways to
> screw up that spec. On a DB25 pinout -- like the kind on Walter's
> Sportster modem -- there are many more ways to complicate things (In
> fact I recall that DTR/DSR hardware handshaking was at least as or more
> important than RTS/CTS, in the heyday of these modems.)
>
> Does the USB-DB9 adaptor support all eight pins (we can do without Ring
> Indicator, but let's not forget the venerable Carrier Detect ;-) )?
>
Don't know. But I did use a USB-DB9 adaptor to interface to a multimeter
that has a serial interface. (I wrote a strip chart recorder program in
Tcl to log data from the meter. A very low-cost way to build a
data-acquisition system.) The multimeter required that RTS be asserted,
not for flow control, but to provide the negative voltage for driving the
multimeter opto-isolated interface! (The damn thing also used a 600 baud
rate, which some terminal emulators don't support!) The Tcl serial control
commands can assert and deassert CTS and RTS, so it was possible to do
that and the usb-serial adaptor (something I got at Canada Computes as I
remember) handled that just fine.

I'd give it a try. USB-serial adaptors are inexpensive and then you can
use your old modem hardware and any software that can talk to a serial
port. Just don't buy the adaptor at the Dollar Store, get one from a
computer dealer.

Incidentally, for troubleshooting a serial port connection, you really
really need a breakout box with LED indicators. And one with jumpers that
so you can read out signals on a scope (our scope is especially nice for
this ;) and cross connect them, is also very useful. I got both those
breakout boxs for a few bucks each at Supremetronic (which became Honson,
which is now a (god help us) hardware store with an electronics section on
College St. (Creatron on College might also be a good bet, or Sayal if
you're up north.)

So, I've had good luck with USB-serial adaptors, but not with USB-parallel
port adaptors. The latter did not work with a Samsung printer.

Peter
-- 
Peter Hiscocks
Syscomp Electronic Design Limited, Toronto
http://www.syscompdesign.com
USB Oscilloscope and Waveform Generator
647-839-0325



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