915MHz RF Walkie Talkies
Nov 2025
Off-the-shelf walkie-talkies are analog FM radios that haven't fundamentally changed in decades. Going digital and adding modern telemetry means owning the full stack from microphone to RF link, which is exactly what made this one worth building. Each unit pairs an STM32L4 with a 915 MHz LoRa modem to handle the full audio chain end to end: microphone into I2S, packetized over LoRa, decoded on the receiver, and pushed back out to a speaker, all gated by classic push-to-talk. Around the audio path, each radio carries GPS for live location, a 6-axis IMU for orientation, an OLED for status and signal strength, and the power management to hold it all together. Everything fits on a 3x3 inch 4-layer PCB inside a custom 3D-printed enclosure. This project was especially meaningful to me as an electrical engineering student because something I used to play with as a kid transformed into my own authentic invention. Partners: Zach B., Hailey K., Alex W.