GTA04 USB OVP, USB charger detect, USB-OTG & 6400, earjack DL_GSM, JTAG

Werner Almesberger werner at
Mon Apr 28 10:18:42 CEST 2008

Andy Green wrote:
> I don't know what all the constraints were for making that external jack
> method in the first place,

I have yet to see a good reason for it :-)

> but it would be far simpler if we can communicate with the GSM chip
> UART fully internally somehow

Way too sophisticated :-) There's exactly one time in the life of the
phone when this interface is used, and that's during calibration at
the factory. We can use test points on the PCB and a fixture with the
corresponding pogo pins.

> We should not connect JTAG to MSP430 and just have JTAG on CPU.  We can
> program the MSP430 using a UART connection.

Hmm, I'm curious what made you change your mind on that. To me this
looks like we're planting a big fat wart on a previously beautiful
solution. I guess Milosch must have told you something scary ... :-(

> Well we can make a debug connector how we like for the prototype, but
> what we need is the FTDI chip on there with USB connection of its own to
> drive the CPU JTAG and provide console.

Yup. I don't think we want to invent any new debug connector. If
there's anything else we need, we're better off if this goes to
test points and then a fixture.

We should develop these fixtures (Milosch's design that can be
easily produced in small series) in parallel to the main PCB.

- Werner

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