A custom embedded hardware project built around an STM32 microcontroller and Quectel EC25 modem.
The goal is to design, assemble, and program a complete phone system from the ground up — starting with hardware validation and moving toward a full integrated board.
Step 1 — Hardware Verification (current step)
- Bring-up of the main board and peripheral circuits
- Validate power rails, charging system, and USB interface
- Test modem communication (EC25) and antenna performance
- Ensure STM32 programming and serial communication are functional
Step 2 — Full System Integration
- Run the STM32 firmware with modem control and battery management
- Implement power sequencing and graceful shutdown logic
- Test full end-to-end operation (voice/data + MCU control)
- Optimize PCB layout and firmware reliability for production
- PCB Design: High-speed routing, impedance control, power delivery, and signal integrity
- Embedded Programming: STM32 firmware (C), peripheral interfacing (UART, USB, GPIO, ADC)
- Power Systems: Battery charging, voltage regulation, and load-sharing design
- System Integration: Combining modem, MCU, and power management into a cohesive embedded system
- MCU: STM32 L4 Series
- Modem: Quectel EC25-AF
- Power: USB-C input, Li-ion battery, charger IC
- Communication: USB, UART, CAN
- Tools: KiCad, STM32CubeIDE