This is a quick-and-dirty sample on how to connect an ESP8266 to Swarm to publish sensor data. It reads A0 ADC pin to calculate a temperature out of a voltage reading.
When run on a device, it will read A0 and publish it to a feed periodically.
Don't expect anything production-ready. The main feat here was to get signatures right, which implied modifying the ethers/uECC library so it would compute them correctly. I tried packaging all feeds-related code in a library "swarmfeed" which I will eventually segregate into its own repository if this sample picks up interest.
You will need Platform.IO to compile this. Other ways are possible, I am sure.
Attach a thermistor to ESP8266's A0 with a voltage divider. Note: this scheme works for most development modules. Other modules may need a max 1V input to A0. Check your module specs.
Vcc(3.3v) --- thermistor --- A0 ---- 4.7k ohm resistor ---- GND
You can also attach some other thing to A0 or modify the sample to read other data.
Modify lib/config/config.h to match your Wifi configuration and set up a private key. This is an Ethereum private key. For Feeds, this private key does not need to have Ether, so you can create as many as you need.
Compile and upload to your ESP8266.
There is also a very simple HTML application that plots the data published by the device on Swarm. You will notice a few config parameters in www/index.html. Make sure you put the Ethereum Address corresponding to the private key you put in config.h.
I will improve this sample with your feedback, find me in Gitter: @jpeletier. Feel free to open PRs to improve this code.
I am not responsible if you break your hardware! Check your connections and make sure you know what you're doing