On Thursday 15 March 2012 15:30:34 Dr. H. Nikolaus Schaller wrote: > 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.
Thanks to your fine documentation I could check that before I posted ;-) The power and unused i2c3 on the test pads looked good. Did I miss a better one? It looks like there's a reasonable bit of space above them in the case too. > 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. I agree that's probably the trickiest bit. Any idea how sensitive the i2c is to the cable? Would a flexible headphone lead type work, or would it need flexi-pcb? > 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: > > http://search.digikey.com/de/de/products/EVQ-P6DB35/P14165CT-ND/1966474 With a thin cover of laser cut and etched stainless, or a plastic part to keep it all from shapeways? Either option would make changing the keymap relatively easy. Also I thought the TCA included ESD protection, although that was just from a quick glance at the datasheet. _______________________________________________ Openmoko community mailing list community@lists.openmoko.org http://lists.openmoko.org/mailman/listinfo/community