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Imported from GitHub: AndreyPodlesni/stm32wl-lora-rf-pcb · commit b93b27d · license MIT

Description

4-layer RF PCB design of a low-power LoRa sensor node based on STM32WLE5CCU6, featuring 50Ω controlled impedance RF routing, SMA antenna interface, and HDC2022 temperature & humidity sensor. Designed in KiCad.

README

STM32WL LoRa RF PCB (KiCad)

Overview

This is a 4-layer PCB design of a LoRa sensor node based on the STM32WLE5CCU6.
It includes a temperature and humidity sensor (HDC2022) and an RF path to an SMA antenna.
The board was designed in KiCad with focus on a working hardware setup and easy bring-up.
The RF section follows the STM32WL development board schematics and layout guidelines.

3D View

PCB Layout

PCB Layout

Key Features

  • STM32WLE5CCU6 (LoRa MCU)
  • HDC2022 temperature & humidity sensor
  • SMA antenna interface
  • 4-layer PCB
  • Battery powered (CR123A)
  • SWD debug interface + UART pins

Hardware Blocks

MCU

STM32WLE5CCU6 with integrated Sub-GHz radio (LoRa).
Combines MCU and RF transceiver in a single chip, reducing external components and simplifying the design.

RF Path

  • RF output from the MCU is routed through a matching network to an SMA antenna
  • RF routing implemented as a 50Ω microstrip based on PCB stackup calculations
  • Matching network includes optional components for antenna tuning

RF Path

Sensor

HDC2022 connected over I²C for temperature and humidity measurement

Battery

CR123A lithium battery used as the main power source

Selected for its ability to handle LoRa transmission current peaks and provide reliable long-term operation in a low-duty-cycle system

Estimated battery life is over 2 years, based on power estimation using STM32CubeMX Power Consumption Calculator

Debug

SWD interface and UART pins for programming and debugging

RF Notes

  • RF traces routed as 50Ω controlled impedance
  • Microstrip routing over solid ground plane
  • RF path kept on a single layer (no vias)

Design Notes

  • Matching network allows antenna tuning during testing
  • Battery selected to support LoRa current peaks
  • Power path prevents back-powering during debugging

Future Improvements

  • Refine RF impedance control by considering copper pour clearance and surrounding geometry
  • Improve sensor placement to reduce thermal influence from other components
  • Further layout optimization for production readiness

Tools

  • KiCad 9

License

MIT