A tool for reading from Hygrochip humidity sensors under Linux
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A tool for reading from Hygrochip humidity sensors under Linux

This is a simple program that queries Hygrochip humidity sensors from Linux. It was developed and tested with the HYT-271, but it should work with the other models that use the same sample code. See my blog post for more details.

To build, just do:

$ make

And then to run it:

$ ./hyt-read
Either the -d or -b option must be present

Usage: hyt-read [ -b I2C bus name | -d device file ] [ -a I2C slave address ]
                [ -i seconds ] [ -T ] [ -H ]
        -b X    Open the I2C bus named X (e.g. bcm2708_i2c.1)
        -d X    Open the I2C device named X (e.g. /dev/i2c-0)
        -a X    Target I2C slave address X (default 0x28)
        -i X    Read data every X seconds
        -T      Print only temperature
        -H      Print only humidity
        -h      Show this message

$ ./hyt-read -d /dev/i2c-1
36.916317 27.065556

The first value returned is the relative humidity as a percentage, the second is the temperature in degrees C.

You can also specify use the I2C bus name (as reported by i2cdetect -l), i.e. on the Raspberry Pi revision 2:

./hyt-read -b bcm2708_i2c.1

The file munin_plugin.sh contains a script contributed by Florian Heiderich to use this program with the munin monitoring tool.