Keyboard for GTA04

Dr. H. Nikolaus Schaller hns at
Thu Mar 15 15:30:34 CET 2012

Am 15.03.2012 um 15:10 schrieb Al Johnson:

> On Thursday 15 March 2012 12:57:23 Dr. H. Nikolaus Schaller wrote:
>> During the "Openmoko Stammtisch Munich" yesterday, we
>> have once again discussed options to build a special GTA04 keyboard.
>> And now I think we have found a way to really square the
>> circle. The square being functionality and the circle being
>> cost.
>> The idea is to use:
>> * off-the shelf pushbutons (Panasonic has some nice and very
>>   flat SMD buttons readily available at DigiKey)
>> * a Shapeways made custom case
>> * a not very sophisticated PCB with the buttons, a Bluetooth
>>   HCI module [1], a small LiIon battery and a microcontroller scanning
>>   the keyboard and supporting USB charging
>> Now comes the key idea: having a shapeways printed case makes
>> it possible to think about a keyboard built into a replacement battery
>> cover. It makes it a little thicker than normal, but you can detach it
>> and use it as a keyboard.
> I was with you up to the bluetooth + battery part. Why not use a slide out 
> keyboard with a TCA8418 and wired i2c connection to the main board? The board 
> should be cheaper and simpler, the plastics little different to a sliding 
> bluetooth device, and there'd be no messing about remembering whether you'd 
> charged the keyboard.

Yes, there are contact points on the GTA04A4 board prepared for this.

My main concern are that cables may break too often and connecting
it to the main board plus getting it out of the device is a little fiddly.

But this could be a cheaper (and easier to develop) option than BT+Battery.
It just needs to place the TCA (plus some ESD-protection) on the board and
a set of buttons like these:


More information about the community mailing list