With only light adhesive holding the base motherboard to its case, it doesn't take us long to pull it out for a closer look.

We rarely see circular circuit boards. It's quite refreshing and alliterates nicely.

The base motherboard is equipped with a surprising amount of hardware for an auxiliary board:

ST Microelectronics STM32L151VB ultra-low-power 32 MHz ARM Cortex-M3 MCU

Sensirion SHT20 humidity and temperature sensor

Texas Instruments LW051A 8-channel CMOS analog multiplexer/demultiplexer