Bello!: Digital 915MHz RF Walkie Talkie

Description
Designed and built a pair of custom walkie-talkies from the ground up, capable of real-time, two-way voice communication over a 915 MHz LoRa wireless link. Powered by an STM32L4 microcontroller, each device runs a full digital audio pipeline from microphone input and I2S streaming to packetized RF transmission, reconstruction, and speaker output, all controlled with classic push-to-talk. Beyond audio, the system packs in GPS for live location tracking, a 6-axis IMU for motion and orientation sensing, and an OLED display showing status, signal strength, and positional data. Everything fits onto a compact 3x3 inch 4-layer PCB with robust power management and lives inside a custom 3D-printed enclosure, delivering real-time wireless audio between the two units. 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 Berthillier, Hailey Kim, Alex Wong
Gallery

Meet Laura (LoRa) and Mike (Mic)!

Final assembled walkie-talkie PCB

3D viewer visualization of the walkie-talkie PCB

PCB back side showing component placement

Complete PCB layout design

PCB layout without ground planes for visibility

Circuit schematic diagram