Custom calypso board

Harald Welte laforge at gnumonks.org
Wed Jul 11 08:26:10 UTC 2012


Hi Matthias,

On Wed, Jul 11, 2012 at 07:55:45AM +0200, Mathias K. wrote:
> Whats your planed form factor of the board?

the core modem design is 40 x 29.8mm in size, but that of course
excludes things like the sim card reader, or any other new components we
may add.

After some first checking, that size would actually even fit nicely
within the mechanical form factor of the C1xx boards, as they have at
least something like 36 x 70 mm mechanical form-factor.

Now if thre was an _easy_ way to make one circuit board that would both
fit into the C1xx case _and_ also have a board edge connector for use in
a back-plane, I would consider doing that.

However, I think that's quite hard.  The modem is likely smaller than
the phone PCB, and there would be a lot of constraints where to have
connectors for battery/sim/speaker/mic/vibrator, etc.

my first idea is to have a 'break away' backplane connector that one
would simply break off to mount it in a phone case.   But then, if it is
intended to be broken (e.g. by perforating with a series of holes), the
PCB might break when it is plugged into the backplane and somebody
pushes it sidewise.

> Do you have choose the concrete calypso cpu already?

Sure, the D751992AZHH.  It seems to be widely available and known.
Contrary to the C1xx designs, it is not a "Calypso Lite", i.e. it has
512kByte internal SRAM and not just 256.

> >  * expose JTAG
> 
> 1.27mm 10 pol Pin-Header on the opposite side of the board edge
> connector, this make it possible to debug the board in a backplane

yes, good point.  However, on that side there is likely the RF
transceiver and the antenna connections :(  You probably don't want the
transmitter near the jtag cable...

> >  * board-edge connector for plugging many boards into one backplane
> 
> I would suggest the ERNI SMC. There are also a cable assembly available.
> http://www.erni.com/fileadmin/medien/downloadcenter/smc/ERNI-SMC-e.pdf

undoubful great connectors, but I really wanted to keep it low cost,
thus the proposalf of using PCIe connectors on the backplane.  Needs no
connector on the board itself, just a bit of board footprint.

> >  * on-board EEPROM for storing persistent data, even beyond NOR flashing
> There are different types available:
> 
> 64KBIT: SOT23-5 - MICROCHIP - 24AA64T-I/OT
> 512KBIT: 8TSSOP - MICROCHIP - 24AA512-I/ST
>
> It is a question of how much memory we need.

thanks, I'm not quite clear on that myself yet.  I just thought it makes
sense to be able to fully erase the NOR flash without impacting hard to
recover data such as calibration.

Regards,
	Harald

-- 
- Harald Welte <laforge at gnumonks.org>           http://laforge.gnumonks.org/
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