[Community] [Gta04-owner] Phone based on raspberry pi?

Dr. H. Nikolaus Schaller hns at goldelico.com
Thu Jul 31 16:45:27 CEST 2014


Am 31.07.2014 um 15:52 schrieb Radek Polak:

> On Thursday, July 31, 2014 15:25:46 Dr. H. Nikolaus Schaller wrote:
>  
> > I just realized this:
> > 
> > 
> > 
> > Unsoldering the USB, Ethernet and the power jack from the BeagleBoneBlack
> > and adding a Display+GSM+Battery cape? Could give a 20-25mm thick sandwich
> > in the size of a GTA04... And the BBB is ~40 EUR. So if someone wants do
> > develop such things, goldelico can give a help to bring it to mass
> > production.
>  
> Hi Nikolaus,
> do you have ideas about the modem which could be used and how to attach it? 

Well, any GSM/UMTS module should fit, though I don't know if USB is available on the header pins.
For GPRS/EDGE an UART is fast enough.

>  
> Nice. Btw few other random things:
>  
> - one of the GTA04 problems is price. Using cheap already built motherboard could be solution?

Not really. 30-50% of the total price is independent of the electronics. I.e. warranty, logistics, packaging,
quality tests, certification, VAT etc. and not to forget engineering cost.

Some components are needed and cost independently of the CPU being a mass produced SBC or
built onto the main board:
e.g. modem, display, battery, speakers, microphone, connectors etc. And the PCB itself.
The PCB could probably be designed using 4 layers which is cheaper than 8.

So without doing a real analysis, I would assume that only 10-20% of the 100% total cost are
affected by the way the CPU is built. So if you leave out the CPU the price of the total system would
go down by 20% :)

The key problem is that everything is too expensive... Because we have so small quantities.
If we could build e.g. 5000 GTA04 boards, they could be much cheaper.

This is why I suggest that someone interested in such a concept really makes a drawing
(block diagram) of such a device so that it lists all (nothing missing! Even some simple capacitors
might cost 30ct each at 200 units) components, looks up the cost of components (e.g. octopart.com)
that are needed and tries to find out what the components cost for 200 units. The sales price required
so that nobody has to subsidize is 2-3 times as high as the pure component cost.

This would IMHO be quite an instructive exercise.

>  
> - there can be community around the motherboard which could help with kernel/SW.
>  
> Another problem is case. 3D printed case for GTA02/GTA04 is hardly usable. It has thin walls that are easily breakable. It also has to be very precise because of earpiece and other components.

Not necessarily. We have a 3D design that nicely fits around the GTA02/04, has required wall thichness and bays for earpiece and speakers etc and works:

http://www.openphoenux.org/ohsw2013/3%20Misc%20new%20from%20GTA04.pdf

Some designer should of course touch the edges... Could cost around 50 EUR per unit if printed commercially.

>  
> But if we design the PCB and other components so that they require less precision then 3D printing/milling would be much easier.
>  
> Btw you dont need HW buttons at all - you can double tap display for waking the phone. Without HW buttons the case can be much more simple and the phone could be water proof.

Well, you need some charging contact pads anyways and maybe a power-on/off button.

BR,
Nikolaus

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