Mobile Broadband - how do I trace/debug the modem initialisation?

[Rick Jones <rick activeservice co uk>]

I have NM 0.7 running on Ubuntu - works fine with LAN & wireless, but I can't get it to talk to a GPRS modem properly. Here's the scenario:

The device is a Palm Treo with Mobile Stream's "USB Modem" installed. This offers a standard modem interface on the USB port, and I can make this work fine using pppd with a conventional chat script. All it needs is AT to kick it off, then AT+CGDCONT=1. etc., all standard stuff.

NM recognises the modem when it's connected, and allows me to setup a Mobile Broadband entry. But when I try to connect I just get "connection failed". Looking at the logs I get:

Activation (ttyACM0) Stage 1 of 5 (Device Prepare) complete
init_done(): Modem initialization timed out
(ttyACM0): device state change: 4 -> 9
.... [various failure / closedown messages ]

It seems to get no response from the modem. This doesn't make sense, as I can minicom to ttyACM0 and manually go through the "AT" dialling sequence!

I've looked at 10-modem.fdi, and I assume it's using the generic GPRS entry at the bottom. I've tried adding an entry with explicit USB IDs but this doesn't make any difference. Using lsusb -v, the device reports that it supports V25ter, which I guess is covered by V250 in the fdi file.

To find what's going on, I'd like to monitor what is actually going to/from the modem, but I don't see any way to do this.

Where are the actual dialling protocol exchanges defined - are they hard-coded? Not being able to script this bit of the connection seems to be problematic, compared to pppd. I'd really like to move to NM instead of messing with pppd, pon, poff etc. but I can't get past the first hurdle :(

TIA for any help/suggestions
Rick Jones