Read temperature and humidity from an HTU21D sensor using node
The HTU21D-F sensor measures temperature and humidity using an I2C interface. The breakout board used for development and testing is the Adafruit HTU21D-F connected to a Raspberry Pi running Raspian.
Be sure to enable support for i2c and install the i2c tools. Adafruit has a tutorial covering this. I suggest adding one more step at the end so i2c can be used without sudo. This step adds the user pi to the i2c group. Logout and log back in to make this take effect.
$ sudo usermod -a -G i2c piThe node.js package in the Raspian repo is too old be used with this module. Adafruit has another excellent page showing how to install the latest node.js version on the Pi.
$ npm install htu21d-i2cvar i2c_htu21d = require('htu21d-i2c');
// If using a Raspberry Pi, do not specify the i2c device name.
// The correct name will be used based on the board revision.
// Older boards use /dev/i2c-0, newer ones use /dev/i2c-1.
// If using any other board, specify the device name.
// For example: i2c_htu21d({device: '/dev/i2c-1/'});
var htu21df = new i2c_htu21d();
htu21df.readTemperature(function (temp) {
console.log('Temperature, C:', temp);
htu21df.readHumidity(function (humidity) {
console.log('Humidity, RH %:', humidity);
});
});This works with the current version of i2c (0.2.1) and node 0.12.0. If using an older version of node, use i2c@0.1.8.
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