[Asterisk-Dev] zaptel fcshdlc extension - need advice

[Steve Brown]

I have a channel bank w/ 8-port bri card connected as 3 zaptel indclear 
channels per bri (3DS0). One bri is configured TE and the other NT. This 
is all hooked to a T100P. I wrote a user-mode program to copy the 
channels in both directions and have been able to place calls over it. I 
used a hacked fasthdlc and a combination of isdndecode and q931.c to 
also trace both sides of the d channel traffic. I'm using this as a 
protocol analyzer to track down some problems with the isdn4linux hisax 
NI-1 code. 

As a next step, I would like to do the hdlc processing in zaptel. 
Fasthdlc is an elegant, table-driven hdlc implementation. While I'm 
convinced that only minor changes are needed, probably to the table 
generators, I sure can't figure what they are.

Could one of the list experts give me some pointers?

The format of the d channel data read from the zaptel channel is as 
follows:

byte 1: 1 1 1 1 1 1 (7) (6)
byte 2: 1 1 1 1 1 1 (5) (4)
byte 3: 1 1 1 1 1 1 (3) (2)
byte 4: 1 1 1 1 1 1 (1) (0)

where the d channel byte is (7) ... (0).

Given this, some repairs to hisax' NI-1 code and a low-level hisax 
driver that talked to zaptel channels, you should be able to place and 
receive isdn calls over any channel bank w/ bri cards. Being able to 
connect to isdn phones is another issue, but there is some interesting 
work by Andreas Eversberg at isdn.jolly.de. He has added NT mode to 
hisax for the euro protocol. Using this as a model, adding NI-1 might 
not be too tough.

If anybody has thoughts about any of this, I'd sure like to hear them.


Thanks,

Steve