MCSI breakthrough

Mychaela Falconia mychaela.falconia at
Sun Mar 31 22:54:38 UTC 2019

> Hi Mychaela and Das Signal,
> Is there a way I could install two audio connectors for MIC and Speaker?
> For the use I have in the lab with the FCDEV3B it would be more interesting.

I am afraid that I don't really understand the question.  Are you
asking for a way to convert the speaker and mic hook-ups on the FCDEV3B
to audio connectors like the ones on a laptop, such that you could then
plug off-the-shelf end-user audio stuff into them?

If that is your question, then I don't have an answer to it, as I am
quite illiterate in the realm of audio myself - just producing the
circuits which are currently on the board was an extremely difficult
struggle for me during the design phase.  Someone who understands
analog audio much better than I do would need to review the circuits
which are currently on the board and figure out what can be done with
them, other than what I found to work.

As I already said before, I would be more than happy to send one of my
voice kits (speaker and mic outfitted with wires and connectors that
connect to the FCDEV3B) to each of you (both Rafael and DS), but if
you desire something different, you will have to figure it out
yourselves.  You will need to start with the Leonardo schematics:

TI's Leonardo speaker and mic circuits are depicted on page 3 of the
above PDF; the corresponding circuits on the FCDEV3B are almost
identical, with only a few differences:

* Where the original Leonardo schematic drawing shows physical speaker
and mic parts, on our FCDEV3B we have a two-post header in the place
of each, for the physical speaker or mic to reside off-board;

* The differential input to the TPA6203A1 loudspeaker amplifier comes
only from EARN&EARP on the FCDEV3B (not from AUXON&AUXOP), and the
gain control resistor values are different, tuned to produce 3.6 V of
swing on each leg of TPA6203A1 output in our configuration when the
output from the Iota ABB (input to the TPA6203A1) is at the maximum;

* C333 and C334 footprints are omitted;

* HSP3xx ESD protection features are also omitted.

The above is all I know; from here onward you have to use your own
audio knowledge, which I lack.

Sorry for being of so little help,
Mychaela aka The Mother

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