FreeCalypso update: progress with DSP patches and voice calls

[Das Signal]

On Sun, Nov 01, 2015 at 10:31:03PM +0000, Mychaela Falconia wrote:
> Hi DS,
> 
> > I redid the tests just to be sure; recompiled and reflashed gsm-fw,
> > then had the GTA02 and another phone register and made a call to the
> > GTA02 handset. I can confirm the voice was fine. I'm using a version of
> > gsm-fw from 2015-10-19 "static DSP patch download enabled by default".
> 
> OK, at least we know now that under *some* conditions (though we don't
> know exactly what they are), our gsm-fw is able to make successful
> voice calls after all.  But you still haven't had any luck with
> connecting to real GSM networks in your part of the world with this
> fw, have you?

Not yet, it seems to fail at the registering phase, however that's
probably because I haven't disabled deep sleep. OTOH TCS211 has no issue
registering. However I just had an idea that could possibly explain why
the phone has problems with real networks but appears to work fine in
a controlled testing environment: power control.

As the phone in my test setup is less than one meter from the antenna,
and as I've configured the output power to have a good signal, the downlink
is probably fine, and I imagine the uplink too (I think OpenBTS also
requests the mobile to transmit at full power). OTOH on a real network
the mobile has to adjust its transmit power very precisely according to
what the network tells it. Any small error in those calculations could
lead to the network not hearing the mobile and a registration or voice
call failing. So a possible course of action here will be to compare the
trace output of both TCS211 and gsm-fw on a real network, looking for
disrepancies in power control.

> > Please note I don't issue AT commands by hand, instead I simply launch
> > the qt-moko GUI.
> 
> Well, it just means that the AT command interface presented by our new
> version of ACI (taken from LoCosto along with the rest of G23M) is
> good enough to make QtMoko happy - good to know. :)

Indeed :-)

> Right now tcs211-c139 is also an ACI-only fw (no UI, control via AT
> commands via fc-shell), but in terms of GSM functionality it works
> just as solidly as TCS211 on its native GTA02 hardware: it registers
> with the network OK, deep sleep just works right out of the box (!),
> SMS works, and voice calls work with perfectly good audio.

That's really good news!

> Thus I feel that creating semi-libre firmware for Mot C139 in which
> the UI code is fully liberated while the GSM radio protocol stack
> components remain object blobs would be a worthwhile FreeCalypso
> subproject.  In fact, from my perspective as an end user who very
> badly wants a libre dumbphone, to me the biggest shortcoming of what I
> propose is not the presence of binary blobs, but the extremely feeble
> nature of Mot C139 hardware.  Switching from Pirelli DP-L10 to Mot C139,
> even if it is accompanied by a firmware change for the better in terms
> of freedom to make UI improvements, would be a major downgrade for me.
> Going from a 128x128 pix LCD to 96x64 pix is a reduction of screen
> real estate by a factor of more than 2.5, and I'm going to *really*
> miss the hands-free loudspeaker - albeit on the Pirelli the usability
> of this loudspeaker is greatly hampered by the stupid proprietary UI
> firmware that refuses to turn it on until the call is answered on the
> other end...
> 
> But the Pirelli is too laden with undocumented hardware to be much of
> a viable target for libre fw - remember the spectacular failure when I
> tried running a port of TCS211 on it.  Thus I still feel that building
> our own hardware is still the *only* way to get a dumbphone that truly
> Does Not Suck.  But semi-libre fw on Mot C139 seems like a reasonable
> interim step to help those who can't wait for our own hw.  And once we
> have this semi-libre fw on Mot C139, I would say building our own hw
> should be a higher priority next step than reconstructing L1 to get fw
> without any blobs...
> 
> Thoughts, ideas, comments?

I completely agree, having even a semi-source firmware running correctly
on this phone model will be useful to draw more people in to the project,
as the C11x/C139 can more easily be found than GTA02, and at a cheaper
price. Also any work on the UI can be reused in gsm-fw, so it's not wasted
time at all. In the end though, I think we should strive for a 100% free
phone (that is, gsm-fw running on our own hardware).

--DS