Re: USB Modem


"David J Dachtera" <djesys.no@xxxxxxxxxxxxxxxx> wrote in message
news:46DF5C8D.3A30E892@xxxxxxxxxxxxxxxxxxx
FredK wrote:


OK. I'll bite. What is a "standards-compliant async serial device"?

See the source code for SYS$TTDRIVER



TTDRIVER is just the class driver. A *port* driver for it must support a
small subset of the actual port/class interface. So it is unclear to me
what TTDRIVER has to do with the price of tea in China. The device itself
is handled by the port drivers - and trust me - there is no "standard" for
the interface other than what comes out the connector on the outside of the
box.


Answer: The only "standard" is what it talks out of the serial wires,
not
the interface itself.

Well, yes and no. What it looks like to hardware is one thing. What it
looks
like to the software layers above that is something else entirely.


What does this have to do with the need for a USB driver to talk to the USB
modem? Do you think "magic happens"? This entire thread was about the fact
that USB modems need a special driver and that not all USB modems present
the same interface to the system, and that the VMS USB modem driver is
written to a specific standard - and to tell the OP what to look for.


A "USB Modem" isn't a serial wire connected to an external modem,

...but for all practical purposes, should appear as such to the
application. A
USB to async. serial adapter could just as easily have a USR Speedster
modem
connected to it as a VT terminal. That's all it needs to look like.


Then it isn't a USB modem. Heck, he could just by a Digi serial dongle and
connect it to an external modem. Or someone could build something that
resembles what you suggest. But who cares? We have code for a specific
type of USB modem.

The fact that my app. needs to converse with it in "AT"-ese is entirely
incidental.


So? My only point here is that what the driver writers assumptions were and
are. When YC (TXA*) is configured, your application can assume by default
that the AT command set is available. If you manage to find a CDC-ACM modem
that doesn't use the AT set, and manage to configure it - you and your
application assumptions are on your own.


We keep trying to overcomplicate everything, then we wonder why we're
starting
to need a 52-hour day.



Seems that you are overcomplicating this.

The OP wanted to find a USB modem that works on VMS. I told him an
(unsupported) driver ships on the system that supports a specific type of
modem, what modem was tested, and what to look for that matches the standard
which we tested.

You want to quibble about the AT command set being needed, and suggest that
serial devices are all standard anyway.



.

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