Description

The TrackFox is an autonomous GPS tracker. The main goals of the project were the following:

• Design a portable device with credit card format, which can be easily integrated in various assets (car, bike, hiking backpack, etc...).
• Embed an accelerometer to detect start and stop events autonomously.
• Achieve the minimum power consumption.
• Use battery-less energy harvesting such as solar panel or dynamo source with supercapacitor.
• Send data over long range IoT networks such as Sigfox.

Hardware

The boards were designed on Circuit Maker V1.3. Below is the list of hardware revisions:

Hardware revision	Description	Status
TKFX HW1.0	Initial version.	❌
TKFX HW1.1	Connect S2LP shutdown pin to MCU to fix startup issues. No more connection from RF TCXO to MCU.	✅

Embedded software

Environment

The embedded software is developed under Eclipse IDE version 2023-09 (4.29.0) and GNU MCU plugin. The script folder contains Eclipse run/debug configuration files and JLink scripts to flash the MCU.

Target

The TrackFox boards are based on the STM32L041K6U6 microcontroller of the STMicroelectronics L0 family. Each hardware revision has a corresponding build configuration in the Eclipse project, which sets up the code for the selected board version.

Structure

The project is organized as follow:

• inc and src: source code split in 6 layers:
  • registers: MCU registers adress definition.
  • peripherals: internal MCU peripherals drivers.
  • utils: utility functions.
  • components: external components drivers.
  • sigfox: Sigfox EP library low level implementation.
  • applicative: high-level application layers.
• lib: Sigfox EP_LIB and ADDON_RFP submodules.
• startup: MCU startup code (from ARM).
• linker: MCU linker script (from ARM).

Sigfox library

Sigfox technology is very well suited for this application for 3 main reasons:

• Data quantity is low, position and monitoring data can be packaged on a few bytes and does not require high speed transmission.
• Low power communication enable energy harvesting (solar cell + supercap in this case), so that the device is autonomous.
• The tracker can operate is very isolated places (mountains, etc...) thanks to the long range performance.

The project is based on the Sigfox end-point open source library which is embedded as a Git submodule.