FCDEV3B loudspeaker and microphone

Sun Oct 15 01:27:34 UTC 2017

> I am also thinking about putting together a mechanically rigid FCDEV3B
> setup that would consist of the FCDEV3B itself, the FT2232D adapter
> for it, the to-be-figured-out loudspeaker and a Li-ion battery that
> can be easily taken out for external charging and put back in, all
> rigidly mounted on a substrate such as plexiglas, so that the complete
> setup with all of its interconnections can be transported as a unit,
> without having to dismantle and reconnect everything. Such portable-
> as-a-unit setup will be absolutely needed in order to test truly
> mobile operation with cell reselection, location updates and handovers
> - I would need to be able to get into a car with this portable FCDEV3B
> setup and a laptop, and exercise mobile functionality while my partner
> drives the car around. But creating this mechanical setup will be a
> lot of work, so it'll be a while before we have it.

What I'd suggest is having a lasercut plate, with the FCDEV3B board 
on standoffs, some 18650 batteries in holders (it's much easier to 
source 18650, they're very stable and don't require any special 
precautions) and a charger board for the 18650 right on the same 
plate, also, loudspeaker and whatever else is desired on that plate.
It's a common setup that we do from time to time to test devices 
at our hackerspace, it's relatively lightweight, cheap (though acrylic
is not as cheap as wood) and easy to design&produce, so definitely 
doesn't count as "a lot of work"  - you can design that in Inkscape and 
produce at the nearest friendly lasercutter-equipped hackerspace.

-Arsenijs

15.10.2017, 02:15, "Mychaela Falconia" <mychaela.falconia at gmail.com>:
> Hello FreeCalypso community,
>
> I have just performed the experiment I've been meaning to do since a
> couple of weeks ago: I managed to connect the loudspeaker and
> microphone that are contained in the handset part of TI's D-Sample kit
> to the loudspeaker driver and microphone input circuits on our own
> FCDEV3B, and tested the resulting operation. The results are:
>
> * When making a test call from this setup, the call downlink audio is
>   heard loud and clear, just like when the speaker is driven by the
>   original D-Sample board, quite unlike the little Soberton SP-1510
>   speaker which was quiet as a mouse. Thus we know that the
>   loudspeaker driver circuit on our boards is fine, no worse than
>   whatever TI implemented on the D-Sample, and the speaker loudness
>   problem was because of a poor choice of the physical speaker part or
>   some acoustical/mechanical issues around that speaker which I am
>   ignorant of.
>
> * I then made a test call to a voice mail system, made a test recording
>   through the microphone, and it sounded just fine when I played it
>   back. This result proves that the microphone input circuit on our
>   boards (which has never been tested before) is also fine.
>
> * In the next test with a real person on the other end of the test
>   call, she told me that my voice sounded fine through this call setup,
>   but there is a strong delayed echo present from the microphone on my
>   end picking up the sound from the loudspeaker. This effect is a
>   very well-known problem with all hands-free call setups, and the
>   Calypso DSP includes an Acoustic Echo Cancellation feature
>   specifically for dealing with this problem. But this AEC is not
>   enabled automatically, and it has a bunch of configuration settings
>   which we have yet to tune.
>
> * As a final test, I uploaded the ringtone melodies in TI's Melody E1
>   format which we've extracted from the TSM30 source to the FCDEV3B
>   and played them through this loudspeaker setup. They played
>   perfectly, confirming once and for all that yes, we can play nice-
>   sounding melodies through a loudspeaker driven by the Calypso DSP,
>   without using an external ringtone generator chip or a piezoelectic
>   buzzer like Motorola and Pirelli phones do.
>
> These results confirm that the loudspeaker driver and microphone input
> circuits on our FCDEV3B are good and not in need of any further
> revision. Thus if anyone buys an FCDEV3B and wishes to have the board
> drive a speaker that is loud enough to be comfortably heard while
> resting on a lab bench, they can be assured that the loudspeaker
> driver circuit on the board is fit to do the job, but they will need
> to acquire the actual loudspeaker part themselves, as I lack the
> necessary expertise to make that speaker part selection. The same
> goes for the microphone input circuit: you'll need to acquire the
> actual microphone part on your own (and use your own expertise to
> select that part), and wire it up to J313 on the board. I am going to
> update Appendix A in the FCDEV3B User's Manual accordingly.
>
> At some point we'll need to find our own loudspeaker part that is no
> worse than the one in TI's D-Sample handset in terms of its acoustic
> output, and figure out what kind of special acoustic/mechanical
> arrangement is needed around that speaker, if any - TI's D-Sample
> handset only exists in singular quantity, and we need to be able to
> put our development kits into the hands of whoever needs one. I will
> try disassembling the D-Sample handset to see the speaker inside, and
> we may also have to hire someone who (unlike me) has a clue about
> speakers and acoustics.
>
> I am also thinking about putting together a mechanically rigid FCDEV3B
> setup that would consist of the FCDEV3B itself, the FT2232D adapter
> for it, the to-be-figured-out loudspeaker and a Li-ion battery that
> can be easily taken out for external charging and put back in, all
> rigidly mounted on a substrate such as plexiglas, so that the complete
> setup with all of its interconnections can be transported as a unit,
> without having to dismantle and reconnect everything. Such portable-
> as-a-unit setup will be absolutely needed in order to test truly
> mobile operation with cell reselection, location updates and handovers
> - I would need to be able to get into a car with this portable FCDEV3B
> setup and a laptop, and exercise mobile functionality while my partner
> drives the car around. But creating this mechanical setup will be a
> lot of work, so it'll be a while before we have it.
>
> Hasta la Victoria, Siempre,
> Mychaela aka The Mother
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