MAX32660 is a very tiny but powerful microcontroller that works almost without external components. Only very view are needed.
a) Supply Voltage between 1.8V and 3.6V (Core voltage will be derived internally) -- blocking caps are beneficial.
b) Ground connection
c) Pull-up + debouncing cap on Reset
d) High frequency oscillator is all internal -- optional 32kHz crystal in case of RTC needed.
d) Debug interface connection: P0.0, P0.1, Reset and GND. UART is optional in case of debug messages via console. Authenticator optional in case of mbed utilization