A LoRa node LMIC example with low power support on STM32.
The example is tested with a RFM95W LoRa module and https://www.thethingsnetwork.org.
- git clone --recurse-submodules https://github.com/fk0815/lora-node-example.git
- cd lora-node-example
- make -C libopencm3 # (Only needed once)
- modify TX_TIMEOUT, APPEUI, DEVEUI and DEVKEY in lora-node.c to match to the node network settings
- make -C lora-node-stm32f103 # build for STM32F103C8
- make -C lora-node-stm32l431 # build for STM32L431CB
If you have an older git, or got ahead of yourself and skipped the --recurse-submodules
you can fix things by running git submodule update --init (This is only needed once)
- libopencm3 contains https://github.com/libopencm3/libopencm3 ARM Coretx-M suppor library.
- common contains debug helper and the hal code with low power support.
- lora-node-stm32f103 contains the example files for STM32F103C8 (as used on Bluepill boards).
- lora-node-stm32l431 contains the example files for STM32L431CB.
- arduino-lmic contains the https://github.com/mcci-catena/arduino-lmic code.
| RFM95W pins | MCU pins | Remark |
|---|---|---|
| RESET | PA3 | |
| NSS | PA4 | |
| SCK | PA5 | |
| MISO | PA6 | |
| MOSI | PA7 | |
| DIO0 | PA0 | on STM32F103B8 |
| DIO1 | PA1 | on STM32F103B8 |
| DIO0 | PB0 | on STM32L431CB |
| DIO1 | PB1 | on STM32L431CB |
The MCU needs to have a 32768Hz crystal for the LSE clock. The timing depends on that. It might be needed to relax the timing by configure a clock error by using LMIC_setClockError() compensate an inaccurate clock.
The project is prepared to support debug prints via semihosting on a debugger. To enable that set the DEBUG=semihost environment variable while compiling the code for the dedicated MCU.
The arduino-lmic requires some patches to allow to compile it free of errors and warnings on a C compiler. Also the HAL API is changed to use ostime_t for all timing related functions. With that a 64bit integer is used for ostime_t to avoid timer overflows.