[Asterisk-Dev] Hardware details for the Digium TDM400P

[Rich Adamson]

> >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.

As a side note if you dig through past postings, there seems to be
more of a sensitivity for digium cards not working well with
some motherboards then there is a sensitivity for processor type.
The motherboard issue is likely related to how the PCI bus is
implemented and/or interrupt handling. There is no known list of
which motherboards have issues.

Rich