Improvment key event detection: In previous version the evaluation of a button event was called in the 100ms callback. Assuming an event is signaled at the in line for 100ms there is a potential risk to loose a button event. To avoid this scenarion the evaluation function was moved into the extint callback (called ~50+xms) and the line readback tim was reduced to 40ms. Reminder: This function is not called in the main loop because the main loop is not executed in UART mode => movement would cause key events to not beeing detected