[gta02-core] Calypso's last dance

Werner Almesberger werner at openmoko.org
Thu Jul 23 19:22:41 CEST 2009

Dr. H. Nikolaus Schaller wrote:
> I think there was already some discussion that an UMTS chipset is too  
> expensive.

There are two problems: the general high cost of 3G and the cost
of using a chipset (R&D and NRE fee).

Using a module trades the latter for a higher per-unit cost. So
this can be a good compromise if we can't make a huge upfront

The general 3G cost remains. The question here is whether we can
continue avoiding 3G and for how long. E.g., I keep on hearing
that 2G is basically dead in Europe.

The moment we drop Calypso, many options are open. So we should
pick what suits us best.

> What about some GPRS module? I think the MC75I was evaluated and in  
> consideration for the GTA03.

Yes, for EDGE, we could use the MC75i. We would have to abandon
the GTA02 case, though, since the MC75i is slightly too big to

So if we drop Calypso _and_ the case, and we choose not to try
going 3G, then MC75i would be a good choice, because we already
know that it works.

Another possibility would be to drop Calypso, maybe keep the case,
stay at 2G, and use a Telit module. Telit are extremely open, which
I find rather endearing.

Here's a comparison chart:

Module			Mounting	Module size	Volume (mm3)
					(mm x mm x mm)	without / with PCB
-----------------------	--------	--------------	------------------
Calypso			On PCB		30 x 40 x 3	   - / 3600
Cinterion MC75i [1]	Socket		33.9 x 35 x 3.3	3915 / -
Cinterion EES3 [2]	LGA		33.9x29.6x3.2	3211 / 4214
Option GTM501 [3]	LGA		25 x 30 x 2.3	1725 / 2475
Telit GE864-QUAD [4]	LGA		30 x 30 x 2.8	2520 / 3420
Telit GE865-QUAD [5]	LGA		22 x 22 x 3	1452 / 1936
Telit UC864-E [6]	Socket		36.2 x 30 x 4.8	5213 / -

[1] http://www.cinterion.com/mc75i.html
[2] http://www.cinterion.com/ees3.html
[3] http://www.option.com/en/products/products/modules/gtm501/
[4] http://www.roundsolutions.com/gprs-modem/ge864.htm
[5] http://www.roundsolutions.com/gprs-modem/ge865.htm
[6] http://www.roundsolutions.com/uc864.htm

Calypso is triple-band GSM/GPRS, Telit GExxx are quad-band GSM/GPRS,
Cinterion are both quad-band GSM with EDGE, and Option and Telit
UCxxx are 3G with quad-band GSM and EDGE.

Main PCB thickness is assumed to be 1 mm, like in GTA02. We did
calculations that suggest that the Option GTM501 would fit in the
GTA02 case if we raise the WLAN module a little. Both Telit modules
are thicker, which may just exceed the available space.

- Werner

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