I2C Humidity Sensor

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General description

The SHT21 from Sensirion is a digital humidity and temperature sensor with a easy to use I2C interface. It connects to your Freerunner just like the I2C Pressure Sensor.

A simple kernel driver is already available from here.


The relative humidity depends on the ambient temperature. This makes it rather difficult to find the best mounting place for the sensor. The requirements are:

  • contact with fresh air
  • minimize errors introduced through heat from other electronic components.

Possible mounting places

  • next to the GPS antenna
  • inside the GSM antenna
  • behind the speaker holes
  • ...

I tried the first two options. After drilling small holes both places can be used, but even without top cover I was able to measure a temperature difference of about one degree celsius between the inside and outside of the case.

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