MCSI breakthrough

Rafael Diniz rafael at
Thu Mar 28 20:09:06 UTC 2019

Thanks a lot Mychaela,

I read the document. Which kind of interface could I use to connect to
the MCSI pins and be able to receive the audio samples in a computer?

Best regards,
Rafael Diniz

On 3/28/19 3:44 PM, Mychaela Falconia wrote:
> Hello FreeCalypso community,
> For those with an interest in the embedded modem side of our family of
> projects, I have some exciting news: after having it on the back burner
> for almost 2 y since our first boards, I finally got MCSI to work in
> an acceptable manner as a digital voice interface.  The details are
> documented in the new Calypso-digital-voice article in the
> freecalypso-docs Hg repository, but here are the two essentials:
> * As verified by hooking up 3 channels of my Rigol scope to MCSI_CLK,
> MCSI_FSYNCH and MCSI_TXD signals simultaneously (all 3 are outputs
> from the Calypso in the "Bluetooth" digital voice mode), I have
> confirmed that the framing format in which the digital voice samples
> are exchanged is indeed what I thought it was - please read my
> Calypso-digital-voice article in freecalypso-docs for the details.
> * The key to having MCSI work successfully as a practically usable
> digital voice i/f is that it must not be enabled continuously, instead
> it requires dynamic control: it needs to be turned on when a voice
> call is connected and turned off when a call ends, so that MCSI clocks
> are running only when the modem is in an active call, and not during
> idle between calls.  As explained in my Calypso-digital-voice article
> in freecalypso-docs, I have just implemented a new mechanism in our
> Magnetite and Selenite firmwares (enabled with the new AT at VSEL=1
> command) that does the necessary auto-switching magic, and with this
> new firmware feature the digital voice interface works reliably: the
> DSP bug that was previously getting in our way is reliably avoided.
> So if you have an FCDEV3B and you are interested in getting a digital
> voice interface out of your modem, you can now give it a try.  You
> will need to compile the latest FC Magnetite firmware in the hybrid
> configuration (I plan on putting out a new official build in the next
> few days), and you will need to read the Calypso-digital-voice article
> in freecalypso-docs for the hardware interface details.
> Hasta la Victoria, Siempre,
> Mychaela aka The Mother
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