[mdlug] Semi-OT: Serial modem behavior

[Jeff Hanson]

Another possibility - they are set for software flow control (XON/XOFF).


On Thu, Jul 24, 2014 at 11:32 AM, Jeff Hanson <jhansonxi at gmail.com> wrote:

> Try 7E1.  115K is generally the max for RS-232 modems since faster UARTs
> weren't common until later eras.
>
> I played around with an old system like that several years ago.  The
> problem I had was its 166MHz Cyrix 6x86 CPU which X wouldn't work with  (on
> Puppy Lite, IIRC).  I had to use TinyX but only one version worked and no
> 3D.  I found that ISA sound cards weren't fast enough for MP3s so I had to
> use a PCI card but even that could only support 24K MP3 streams.  I was
> lucky and had a 56K v.90 USR ISA modem with a controller and it acted as a
> serial port.  The only graphical web browsers that were usable was the
> embedded version of Konqueror and maybe Dillo.
>
>
> On Thu, Jul 24, 2014 at 8:42 AM, Ingles, Raymond <
> Raymond.Ingles at compuware.com> wrote:
>
>> I have access to three serial modems, all different models. One of them
>> works just fine - a USR Sportster. The other two (a Zoom 2400 baud, and
>> another 14.4 modem whose manufacturer escapes me for the moment) display
>> the same problem - no data coming back from the modem to the computer.
>>
>> Cabling doesn't seem to be the issue; the same cables work with one
>> modem, but not the other two. I've used a couple different cables, and used
>> both USB-to-serial adapters and on-motherboard serial ports.
>>
>> The behavior on the two problem modems is the same. Using a program like
>> 'minicom' or 'gtkterm', I can see the modem notice things like DTR and such
>> - the appropriate lights turn on. When I send AT commands, I can see the RD
>> and even SD lights blink. Yet absolutely no response shows up in the
>> terminal. On the working modem, I get responses without issue. But on the
>> failing ones, nada.
>>
>> I've tried bauds from 300 to 115200. (At higher bauds, the non-working
>> modems RD and SD lights stop blinking.) I've pretty much stuck with 8N1
>> parity, but if anyone has suggestions for alternatives there I'm curious.
>>
>> Obviously the use cases for serial modems are... pretty rare these days.
>> But I've got this 'dream machine from 1993' that I occasionally bring out,
>> and a functional serial modem would be a lovely thing.
>>
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>
>