pIO series input-output board for the natWatch platform with four SPDT signal relays


  • QWHD size (25x80mm)
  • very low power consumption in sleep mode
  • 4 bistable signal relays with feedback

Front connector pinout

Top row Signal Battery NEG Battery NEG/temp sensor NEG Solar panel NEG
Pin 8 7 6 5
Bottom row Pin 4 3 2 1
Signal Battery POS Temp sensor POS Solar panel POS

Maximum ratings / electrical characteristics

Ambient temperature -40 - 60°C

Implementation details

The extension board is connected to the rest of the system using the UXB bus (SPI multi-master) as specified in the natWatch specification. All communication is handled using a STM32L011K4T6 microcontroller in a LQFP32 package with 16KB of program flash memory and 2KB SRAM. All 4 relays have bistable contacts with set and reset coils. The coils are driven from the 5V UXB bus power with a MAX4820 8 channel relay driver. As the relays are bistable, one half of each is used as a feedback to the microcontroller.

The used relays are Zettler AZ850P1-5.

  • pio-relay-s4/index.txt
  • Last modified: 2018/09/15 08:15
  • by qyx