[gta02-core] Calypso's last dance

Álvaro Lopes alvieboy at alvie.com
Fri Jul 24 11:36:16 CEST 2009

Dave Ball wrote:
> Stefan Schmidt wrote:
>> Sure. I would not even start to design for it without the docs. Maybe they also
>> have other interfaces you could use. 
> Sure, the proper design work will be done after getting a look at the 
> docs, and working out if the device really will work for us.  From the 
> public info and brief contact we've had with option it looks like there 
> is a good chance of making it work (and in the current case etc.) - if 
> we can reach an agreement on our openness needs.

This is good news.

> There's quite a few GSM modules out there, but most of them seem to have 
> the same show stopper for us - size.

Is height the only showstopper here, or do we have concerns about PCB area too ?

> A long way to go with this, but the calypso has it's own problems too.  
> We're currently stalled on the modem front because we can't get TI's 
> docs or reuse the existing design - and even if we could, the part is 
> EOL and v. difficult to get hold of.  My feeling is that if we _can_ use 
> the option it'll both work around the calypso problems, and give us a 
> more interesting device (3g).

I'll be honest here. I see Calypso as a dead end. I think since we came this far, and with so many modifications, we should look at alternatives as if they are
not alternatives, but the only way to go. Even if we don't find any I don't sincerly think we can get Calypso to work by other means than speculative. And lack
of UMTS is a real killer. People laughed at iPhone for much less than this (lakc of ability to send MMS - which turned out to be software, not hardware AFAIK)

> If we want to do 3G for whatever comes after -core, prototyping with 
> this device now will give us some experience, and give some of the guys 
> currently producing software a headstart in working out how to best use 
> the extra functionality.

Changing the GSM chip is perhaps not as radical as we might think. My worries are mostly about power consumption. [I'm investigating how to get those 3A peak
without disturbing the PMU too much, in case we go after option's chip]

A question for you all: if we have one decision on top of the table like: "Shall we go for a 3G GSM chip, for which we have enough documentation, and drop WLAN
module, or keep the WLAN module and blindly integrate our old, EOL, obscure GSM 2G chip ?" what would we choose ?

We are likely to be forced to decide things that actually will negatively impact functionality. But that's engineering - weighting pros and cons, and make
balanced decisions. So far it has been easy - we always had more to gain than to lose.



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