In article <[EMAIL PROTECTED]>,
Alan Cox <[EMAIL PROTECTED]> wrote:
>Digitals soft modem package for the ARM claims to use 25% of the CPU power
>of a 200MHz strongarm - not trivial.
That 25% of CPU time is probably non-interruptable too, in order to
meet the strict realtime requirements of most of the line protocols.
You wouldn't want your modem to stop for network I/O in the middle of
an equalizer retrain sequence, for example. You'd also be using that much
CPU time all of the time that you are connected, not just when you're
receiving data.
>More to the point no vendor has yet provided any useful information to enable
>people to write them.
I would suspect that there's very little information to know about the
WinModem itself. It's probably just a DSP (or even just a simple pair of
FIFO buffers) with D/A and A/D converters and a few bits of I/O ports on
the side (e.g. for the hook switch relay). It would not be significantly
more difficult to write a driver for one of these things than it would
be to write a driver for a sound card, assuming that you had specs on the
hardware.
The _hard_ part is writing signal processing code for speeds above
2400 bps without at least an oscilloscope and access to a library full
of patents. You'd probably want to have good multi-input data capture
and analysis hardware too, unless you really like challenges.
I'm not going to even think about how you'd get your jurisdiction's
regulatory approval for the resulting software and hardware combination.
The hardware is probably built so that no matter what you did with it
you'd be within the physical specifications, but many jurisdictions have
requirements for the software and also require that it not be possible for
the software to be trivially modified in violation of the regulations.
--
Zygo Blaxell, Linux Engineer, Corel Corporation, [EMAIL PROTECTED] (work),
[EMAIL PROTECTED] (play). It's my opinion, I tell you! Mine! All MINE!
Size of 'diff -Nurw [...] winehq corel' as of Mon Feb 22 11:14:00 EST 1999
Lines/files: In 2948 / 53, Out 29300 / 428, Both 31518 / 461
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