Tiny WIP Rasperry Pi Pico W sensor monitor written in Rust.
This code utilises the built-in Pico W wifi chip to send the connected sensor data to a remote API endpoint. A simple POST request, containing JSON body with the data, is sent at a specified interval. (by default every hour)
The code is build on top of the Embassy framework: https://github.com/embassy-rs/embassy (as at the moment it seems to be te only available Pico wifi drive for Rust.)
DHT-22 is one of the two sensors supported in this repo. The driver has been written to be compatibile with the Embassy framework and uses it's FlexPin for serial communication.
(the communication requires the very same pin to be both read and written to)
Even though Embassy is an async framework, the DHT-22 is read in a blocking manner. During my initial tests I have realised that the serial communication pulses are to short in time to let the code return to the async loop. (packets were lost)
WARNING: the sub-zero temperatures has not been tested in real life and are potentially not implemented correctly. The documentation for my version of the DHT-22 sensor did not mention how the negative values are encoded. On the web you can find at least a few contradictory pieces of information on the subject (probably due to different sensor versions). I had to pick one, but could not test it yet.
A simple capacitive soil moisture sensor is a second part of equipment included in the code. (although it should work also with the resistive one's - as its just a simple analog read).
The ADC has not been implemented yet for the Pico W in the Embassy Hal, so the implementation here is done rather at the PAC level.
In order to build or run the code a number of env variables has to be set:
WIFI_NAME=SSID
WIFI_PASS=SECRET
HOST_NAME=0.0.0.0
HOST_IP=0.0.0.0
HOST_PORT=80
HOST_PATH=/api/report_endpoint
The HOST_NAME variable can often be a domain rather than IP - if the server is public. The DNS resolving is not implemented though - so the IP has to be specified in the POST request regardless.
As it is not handy to write those down every time, they can be stored in an .env file and loaded while running Cargo via:
env $(cat .env) cargo run --release
A run.sh script containing the above command is also included in the repo.