A DIY stand-alone unit for watching geofence breach is made by using Teensy 3. The general purpose device, which has a similar functionality of geofence or sending notification by location on smartphones, is also usable to automatically start/stop recordings of GoPro camera with aid of MewPro.
Although each MewPro has a microcontroller (AVR) on its board, we decided to separately use Teensy 3 (Cortex-M4) that can do with double-precision floating-point (64 bits) numbers. Implementing geofence as stand-alone enables the unit to control not only GoPro cameras but also other equipments (such as LEDs and buzzers) with regard to preconfigured geofence, which can be a union of convex polygons.
To test the unit we connect an LED to its alarm pin:
SHUTTER signal (red wire) at the audio mini plug in the photo becomes LOW/hi-Z if it enters/exits the geofenced area. We use digistump’s ATtiny85 Digispark board to watch the pin and to turn on/off the LED, however, you can use any device such as GoPro+MewPro or something as Digispark.
The following is a teardown of the DIY unit.
The module is an open software/hardware. The schematics and the source code with a simple README document are downloadable from: