Based on a Pycom gpy (Bluetooth, WLAN, LTE) ESP32 MicroPython board and its associated Pytrack module that has a L76 GNSS module (and LIPO battery charger). This project needs a Daughter board.

• Be very, very low power (17uA when asleep with GNSS VBACKUP powered)
• Chargeable from 12-24V
• Rechargeable LIPO battery for easy parts sourcing
• Has a button to enable user wake up
• GNSS For location
• LTE for Coms
• BilgeSwitch and Temp (DS18B20) Alarms
• LED for Status (in switch)

• Frequent
  • BilgeSwitch state
  • Temp above / below threshold
  • If in Alarm, send coms
• Less Frequent (less likely to change frequently)
  • Position
  • Battery volts
  • VCC volts
  • If in Alarm, send coms
• Daily
  • All of the above and sends status

• Pycom Gpy
• Pycom pytrack
• Mini Step Down Regulator Voltag Power Supply Module 4.5v~55v to 5v
• DS18B20 Waterproof Digital Probe Temperature Sensor with Silicone Cable (higher temp) Thermometer
• 12V 12mm LED Power Push Button Switch Momentary Waterproof Metal 4 Pin
• 1200mah LIPO Battery
• Bilge Switch (any normally closed, simple switch would do)

The Daughter board fits between the Gpy/Fipy and Pytrack module via headers (see pictures when I add them). It is designed to hold certain parts and expose some pins via headers or JST connectors. Its footprint is similar to the Pytrack to keep space requirements down.

The Daughter board mounts;

• VCC voltagedivider connected to an ADC pin to measure VCC
• Switchable Regulator with ENABLE pin connected to a pin
• JST(s) to breakout the relevant connections for the 11-36v VCC+GND, LED, Switch, DS18B20 Temp module, BilgeSwitch, 5V+GND for the Pytrack USB port
• Note we will be putting 2x5pin XH JSTs on the Pytrack External IO to use those as well (simplifies this board and makes it smaller)

See the eagle files for the details.

• https://blog.yavilevich.com/2017/03/efficient-dc-12v-to-5v-conversion-for-low-power-electronics-evaluation-of-six-modules/