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Driver crate for the HTU21D temperature and relative humidity sensor. I made this crate because I got a sensor for an upcoming project and didn’t find any crate for it. Turns out there is a crate, but oh well. It’s still been a learning experience.

It’s been my first time working with I²C directly, and implementing this crate from the datasheet was quite a bit more complex than the the 3642bs one. Just like that crate, this one is also compatible with all embedded_hal-based HALs and probably Embassy.

For now, the crate includes these functions:

  • .temperature() does what you’d expect. It sends a request to read the temperature, waits for the sensor to take the measurement and then reads the I²C bus for the reply. It puts together the bits of the answer and does the required math from the datasheet.
  • .humidity() is the same story as the previous, but it returns the relative humidity instead.
  • .dew_point_temp() calculates the dew point temperature, which is the temperature to which the air would have to be cooled to become saturated with water.

This is the first thing I made after finishing the rust book and ruslings exercises, so I’ve made use of generics a bit more consistently with this one. It’s still far off from perfect. I’ve still had to fight with the compiler and ended up with not exactly what I wanted. Because of how the generics work, I couldn’t unwrap, debug print or impl From the errors. Despite this I haven’t insisted on fighting with it, because I needed this ready to be used ASAP. I wanted it to build a project with the ESP32-C3, but turns out the I²C on it is broken, so that sucks.

I don’t have much else to say about it, so I’ll leave it here.

Check out the project on gitlab: