FreeCalypso update: progress with DSP patches and voice calls

[Das Signal]

Hi everyone,

Sorry for the late update (had to brush up a bit, my FC skills were
a bit rusty ;-) Anyhow I performed a series of test intended to
make sure my setup was in working order and to evaluate gsm-fw with
Mychaela's new static DSP patch.

Firstly I flashed back leo2moko (gsm-fw.m0) and had the phone connect
to a real network; as expected, everything worked fine. I then
switched the SIM and started OpenBTS. The phone had no particular
problem registering, and both MT and MO calls worked fine. At first
I thought something was wrong since fc-shell wouldn't respond to AT
commands, but then I realized I should have flashed leo2moko-debug
instead of the regular leo2moko.

Then I compiled the new gsm-fw and flashed it, then had the phone
connect to the test network and place a phone call, using Qt's GUI.
The good news is that everything worked fine! The other phone rang,
and the audio was of good quality. It seemed however that a noise
cancellation feature was present in leo2moko but not here: the noise
floor felt higher, as well as the Larsen effect. Hopefully this is
something we'll fix with the dynamic DSP patch and/or L1 rewrite.

Finally I tried registering gsm-fw on a real network, but it didn't
work (registration does not go through); I'm not sure why, a proper
investigation will be in order.

--DS