We wanted to see if it was possible to eliminate the physical buttons on the front of the phone by using a capacitive button panel.

It has a few advantages:

• At this point in time, it's what people expect (it looks good)
• If we do it right, it could be easy to let people swap out a PCB with a different button layout, opening up the ability to adapt the hardware to different purposes.
• Potentially longer design life, due to no moving parts

Disadvantages:

• Somewhat risky. Physical button panel examples are everywhere, but you don't generally see capacitive button panels as dense as we need. There's probably a reason for that, so we expect to have issues with crosstalk/inadvertent triggering of neighboring buttons.

We made a test panel, shown above, that has buttons of approximately the size and pitch we need for the phone. Overall, the test panel works OK. It is, in fact, easy to accidentally trigger neighboring buttons. But it was interesting enough we'll go ahead and make another panel using our current button layout and see how it performs in the phone.