• Double-Sided PCB Board
• 22AWG Solid Core Wire
• 60/40 Rosin Core 0.5mm Solder Wire
• 1/2" Kapton Tape
• Non-Static Sponge

For this project, I decided to use a Teensy 4.1. The large amount of pins, combined with the beefy processing power and the on-board SD card reader was the winning combo.

• Radio: Adafruit RFM69HCW Transceiver Radio Breakout 433 MHz
• GPS: Adafruit Ultimate GPS Breakout
• SD Card: 32GB

• NeoPixel Ring - 12 x 5050 RGB LED
• Piezo Transducer - 15V Buzzer
• ADXL377 - High-G Triple-Axis Accelerometer
• MS5611 High Resolution Atmospheric Pressure Module

To power the on-board computer, a 3.7V LP963450 1800mAh battery was connected to a PowerBoost 1000 Basic 5V USB Boost via a USB to MicroUSB cable to the Teensy MicroUSB port.

The Ground Computer was a much simpler set-up, made up of an Arduino Uno and an Adafruit RFM69HCW Transceiver, connected via a breadboard and connected to a laptop.

1. Plug in the Battery

   Once the battery is plugged in, the set-up method begins. The NeoPixel flashes up, confirming that power has been received.

2. Run Set-Up of Sensors

   Each sensor will be initialised. If a sensor is connected and working correctly, two lights on the Neopixel will show green. Otherwise, they will show red. If all lights are green, all sensors are initialised correctly.

3. Where am I?

   The GPS sensor will now search for a Satelitte fix. This can take up to 10 minutes, and the sensor needs to be outside. Once fixed, a success tone will play.

4. Time to collect data

   Now that all the sensors are tested, every 200 milliseconds, the main loop will request a reading from each sensor, and write them to the on-board SD memory card.

5. Ground control to Major Tom!

   Every 8 seconds, the on-board computer will send the last reading of longitude and latitude data to the ground computer.

   The ground computer will send back an acknowledgement for any packets received.

6. Rescue me!

   After the altimeter reads a height higher than 500m, the rescue tone is added to the loop, and will keep going until the rocker is rescued