[Asterisk-Dev] Hardware details for the Digium TDM400P

[Leo Ann Boon]

>It has to go in a Via EPIA system with their C3 (Nehemiah core) processor at
>1.2ghz (with full speed FPU). That's supposed to be equivalent to a
>similarly clocked P3 or Celeron. 
>  
>
I've 2x TDM04B (that's the 4-FXO version) running on a Mini-ITX CL10000 
mobo with 1GHz Nehemiah. Just make sure you have a casing with 
sufficient power. I'm using the C137 with 90W PSU. I'm planning to 
switch to C146 rackmount, in order to use 2x3.5" HDD. 2.5" HDD are 
mostly not built to run 24/7 - unless you can buy those 2.5" HDD built 
specifically for blade servers. Those babies are are pretty hard to come by.

>
>I wish that Digium would make just a one or two page "how it works" doc
>about the card and card-driver interaction. What registers does it have, and
>what do they do? When are interrupts generated, what for, and how frequently
>per call? Does it use DMA, and how? What does it do well? What does it do
>poorly? What could be improved on in the driver? How does the driver do
>things? You know, just basic stuff.
>
>It's not nice having to guess from driver code, which is hard to understand
>(esp the DSP code), possibly bug ridden (no offence) and not guaranteed to
>fully utilise the card's hardware facilities. A little bit of info would
>make understanding the lower levels of the software much easier.
>
>  
>
The TDM cards are just DAA (for FXOs) and ProSLIC (for FXS - Si3210) 
connected to the PCI bus. These chips do not have any on-board DSPs, 
they just read and write PCM data.  The PCI controller on the card 
exposes most (if not all) the DAA/ProSLIC registers for programming. 
Read the DAA/ProSLIC datasheet for more details. All DSP functions (like 
Goertzel detectors) are implemented at the host side - think soft modem. 
The Zaptel DSP library is written in C and is pretty easy to understand 
(assuming you already know all the mathematics involved). IMHO, the 
Digium cards are the easiest telephony cards I'd every worked with. I've 
had DSP cards that require a custom firmware from the manufacturer to 
handle our local call progress tones. With the Digium cards, I just edit 
the zaptel source and voila.

Just my $0.02.