I'm breaking my normal signature disclaimer for this post. dirkvl: Good work that you have done. We have been following your progress with high interest and we don't want to slow down your progress. I asked around for permission what details I can reveal to make your work easier. So hopefully following details will help you to continue your development. - 3,3V VDD (max 300mA, preferrably < 150mA to avoid thermal issues) - 1,8V I2C (400kHz default setting in kernel) - Other half expected to work in slave mode, phone is master - Dedicated INT GPIO (1,8V) for interrupts Further details and API examples will be published at later phase on coming SDK releases. We are quite busy making the magic to happen, so even though sometimes our answers might sound vague, we are trying be as open as possible and try not to give out wrong information. Having said that, don't shoot me, if I make typoes... I'm hoping to see nicely working hardware keyboard as end result of this project