digital audio to FCDEV3B

[Serg l]

Mychaela,

It is a good point that DSP code may not support this functionality and
some preliminary tests will be needed.
I started looking into this and based on C155 service manual schematics
MCSI is actually exposed on J2 and apparently used for some sort of tests
(I seen this mentioned in docs), hence I can try to experiment with that
using another SPI host.
For my application I would prefer to drive MCSI from the external host and
use it in multi-chanel mode, which seems to be available based on DSP
config parameters.
​
 image.png
<https://drive.google.com/a/tvman.us/file/d/0B-LGWaryBRksX1pOcmJHZUJUY0lkN2hIZlBZM3g3N1FDVi13/view?usp=drive_web>
​
-Serg

On Tue, Jan 3, 2017 at 3:29 AM, Mychaela Falconia <
mychaela.falconia at gmail.com> wrote:
>
> Hi Serg,
>
> > I guessed that VSP looks like a private interface, however MCSI is not
very
> > well explained in the docs, so I clearly overlooked this option.
>
> Indeed the MCSI is not really documented properly anywhere, there are
> only passing references to it, but here is the understanding I have
> reconstructed so far:
>
> * In pure hardware terms, i.e., in terms of the capabilities and
>   limitations of the unchangeable silicon rather than changeable
>   software, MCSI is a totally generic synchronous serial interface.
>   It is connected to the DSP side of the Calypso, not the ARM side,
>   but the DSP is still a processor that runs code, and the code
>   executing on the DSP has the freedom to configure and use the MCSI
>   hardware however it likes, for any arbitrary purpose, not just
>   "Bluetooth" voice.
>
> * The DSP runs code from its mask ROM by default, but the patch
>   mechanism has the ability to override any part of it, thus the
>   ability to run your own code in the DSP and use the DSP's hardware
>   in ways other than how the ROM code uses it is quite real.  But it
>   is very difficult to exercise this capability currently, because
>   writing downloadable patches for the ROM code requires understanding
>   the base code to which these patches need to apply, and we have no
>   source and no symbolic COFF file for the DSP ROM code.
>
> * It is not immediately obvious whether the DSP code for using MCSI as
>   a "Bluetooth" interface is already there in the ROM in the silicon,
>   or if it is a part of the patch code downloaded by TI's TCS211 fw
>   and replicated in FreeCalypso.  When we get the hardware built and
>   thus gain the ability to experiment, we may be able to answer this
>   question experimentally by disabling the DSP patch code download and
>   testing if the "Bluetooth" mode still works.
>
> > I will look into BT application for proper SPI parameters and data
formats.
> > If you could suggest any docs on FTP to aid this activity it will be
> > greatly appreciated.
>
> Look in this directory:
>
> ftp://ftp.freecalypso.org/pub/GSM/LoCosto/FGW/
>
> Download LoCosto_hw_sw_docs.tar.xz; amongst various other docs you
> will find schematics for TI's I-Sample reference board.  It is LoCosto,
> not Calypso, but it does have TI's Bluetooth Island chip connected via
> MCSI, so you can see how it's wired.  BTh.zip contains the docs for
> that Island chip, but the datasheet I read says that it supports many
> different data formats for the digital voice channel, so it still isn't
> clear which format is used by the Calypso DSP code (be it ROM or patch)
> that configures the MCSI for "Bluetooth" operation.
>
> So it looks like we will need to reverse-engineer this aspect once we
> get the hardware built.  Start by putting an oscilloscope probe on the
> MCSI_CLK pin and seeing what clock frequency it puts out, if any.  If
> no waveform at all is visible, then it would imply that the DSP code
> put the MCSI into slave mode, requiring an external clock - provide
> one in that case.  Once there is a clock running, either Calypso-
> generated or externally supplied, see what the bits put out on
> MCSI_TXD look like...
>
> > BTW do you have mechanical drawings of FCDEV3B with positions of
mounting
> > holes and headers? I could not find it on FTP. I was thinking to start
> > working on the standalone enclosure and mounting brackets for integrated
> > installation.
>
> Such a mechanical drawing has never been created; if you are going to
> be creating one, the position data will need to be extracted from the
> PCB gerber and NC drill files, or from the Altium PcbDoc file if you
> are able and willing to run that Weendoze proprietary software.
>
> M~
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