[Asterisk-Users] Major problems with TDM400 and specific telephones: suggestions?

[John Novack]

Rich Adamson wrote:

> <snip>


> If you draw a schematic of the fxo module on the TDM card, its almost 
> exactly like the tech note schematic for the Silicon Labs chipset.
>
>First guess is that was the starting point for whoever built the
>card and modules for digium.
>
>It appears on the surface that whoever did the design and layout
>is not an industry leader in professional hardware design, but there is a lot of room for opinion in that statement. Part of that stems from a missed circuit board trace on the E/F model, noisy reset line between the pci controller chip (Tigerjet) and the fxo modules, pci controller loses its ID, etc.
>
>I've improved the stability of my card by adding a capacitor on the
>reset line. Hasn't taken a hit in over two weeks.
>  
>
Is this the E/F or revised H card? Where and what cap did you install?

Also, when the driver is loaded, my system reports an E/F card, but the 
board clearly says "H"
Anyone know for sure which is correct.

>There is also major differences when comparing external gateway
>products to the TDM card, and most of those difference involve 
>the controls inherient to dedicated microprocessors (or controllers)on the gateways, verses asterisk's approach of relying on the host processor for everything (and it's associated uncontrolled/unknown pci motherboard structure).
>  
>
As illustrated by the problems this card has with PCI slots. Even some 
motherboards which clearly are PCI 2.2 can't see the card in ANY slot.

>On top of all that, the drivers for the card (as of right now) are
>the bare minimum functions needed to make the card function. The
>drivers have never been extended to preload the chipset's registers
>as documented in the SI tech notes.
>  
>
SOme additional problems related to the driver(s) , but probably are not 
of concern to most, are the way in which the driver detects pulse dialing.
Several of us are using Asterisk boxes as something like a private SS7 
interface to interconnect electromechanical switches throughout the US.
The FXS module is configured as a ground start device to provide dial 
tone to an EM switch, as well as an inward path. Multiple FXS modules 
would allow multiple connections, and GS is normally used to prevent 
GLARE, or head on collisions on the outside chance that several calls in 
and out occur at the same time.
Digium support person #1 has stated that GS does not work  on this 
module, and support person #2 says " it should work"  In fact it does 
provide a GS trunk that works well for outgoing calls. On incoming 
calls, the module does not behave properly, in that before ringing 
begins, Tip should be grounded, and stay that way throughout ringing and 
answer. In fact, Tip seems to float somewhere during the ring cycle, and 
providing an external ground causes ring voltage to cease but not trip 
ringing.
Also dial pulse detection seems very narrow, and different dials that 
work fine with much other equipment is not so with this card.

That said, it seems this is one of the few FXS devices that even support 
pulse dial at all.

It is just another indication of the fairly weak efforts  regarding this 
card, and it seems also for the IAXy module

>If you want to play around with the card, download the pdf files
>from www.silabs.com for the chipset on the card. Then take a look
>at zaptel/fxstest.c to dump the registers to better understand
>how the chipset registers are loaded. You'll need to complile that
>code as a standalone app and run it when asterisk is not loaded.
>
>Trying to follow the code path for a functional TDM card is not
>to be taken lightly. Code is scattered across multiple drivers
>and buried in asterisk modules. Even those that consider themselves
>good asterisk developers stay way from this one.
>  
>
That doesn't bode well for any corrections, does it.

Also, FWIW - GE branded telephones are, and have been since their 
introduction, JUNK!
For a quality 1,2, or 3 line POTS phone, with or without answering 
machine, Panasonic is the one to buy.


John Novack

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