smartmeter-lora

Sends data from a smart power meter to homeassistant via LoRa

• implements listen-before-send to prevent interference with LoRaWAN or other devices.
• the current config uses SF7BW250 and sends every 60s which is reasonably above the 1% duty-cycle from Germanys regulations
• encrypts data using ChaCha20-Poly1305

Requirements

• rustup: so you can install the nightly version required by this project
• cbindgen: The CLI, for generating C bindings to the SML library
• rust-src for the currently used toolchain. E.g. rustup component add rust-src --toolchain nightly-2022-07-01-x86_64-unknown-linux-gnu
• poppler: Provides pdftotext which is used to convert the SML specification to code
• Zephyr RTOS dependencies
• Currently, the build system builds the rust part for thumbv6m-none-eabi but it should be easy to extend if more platforms are needed

supported boards

b_l072z_lrwan1

Very useful for development but maybe a little expensive and physically large.

heltec_lora_node_151

Seemed like a good idea at first but is a VERY BAD choice and only kept for reference of how to use this board in zephyr.

• doesn't have a cryptographically secure RNG(Random Number Generator). My implementation uses an insecure way to turn the temperature sensor into entropy.
• it's support in zephyr is pretty bad(no USB, no power management, consumes 6mA in idle)
• power circuitry is excluded from the schematics
• official documentation

encryption key

generate

openssl rand -out key.bin 32
objcopy --change-addresses 0xf8000 -I binary -O ihex key.bin key.hex

flash

west flash -r openocd -d build-send --skip-rebuild --hex-file key.hex

Run lora2mqtt

lora2mqtt --port /dev/ttyACM0 --baud-rate 115200 --key /path/to/key.bin --mqtt-uri "tcp://127.0.0.1:1883"