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This post will likely seem like a rehash commercial praise of Adafruit, though I only mean it to record the basic information for a DIY mobile phone.

lady ada over at Adafruit has a guide for a DIY mobile phone project. It looks about the same level of complexity as the PiPhone, except explicitly with an Arduino instead of an ARM system-on-a-chip controller. The parts for the entire guide total up to about 120$US. For a 3G radio, it costs around 30$US to 40$US more, depending on the GSM module.

The basic kit involves the following parts:

Essentially, to reiterate the design, the phone has a touch screen interface to the main controller, in this case the Metro board. The main controller then tells the GSM to make calls, and if I understand correctly, to pass SMS messages, and to receive events such as incoming calls, messages, and GPS information if the GSM chip has it built-in. The actual call audio happens via the GSM chip, as far as I can tell, though because these GSM chips also handle data, some of them 3G, the main controller should also have the ability to VOIP.

At this point I have not actually started building anything yet, for either the Arduin-o-Phone or the PiPhone. Still waiting for parts.

From a freedom perspective, the FONA 3G GSM module, for example, has links to drivers and hardware specs. I have not seen the explicit license for the GSM module. I delayed this project many times while looking for the best case for libre hardware and software. I think this finally gives a sufficient set, a little better than the PiPhone which lacked some explanation of the GSM module itself. However, using the resources from Arduino and Adafruit I think I could just combine the better parts of each project.

Note particularly for that module: lady ada recommends beginners start with the FONA 80x series, so for the moment I will probably mind that advice.

At this point, I feel like the form factor of the assembled device should come in quite a bit smaller than I originally envisioned. Perhaps closer to a double-deck of cards instead of a 1980s phone.

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