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@agilatech/zetta-htu21d-linux-driver

0.9.3 • Public • Published

Zetta htu21d humidity and temperature sensor driver for Linux

This driver should work on any Linux platform, and has been thoroughly tested on BeagleBone Black

Install

$> npm install @agilatech/zetta-htu21d-linux-driver

OR

$> git clone https://github.com/Agilatech/zetta-htu21d-linux-driver zetta-htu21d-linux-driver

Usage

var zetta = require('zetta');
var htu21d = require('@agilatech/zetta-htu21d-linux-driver');

zetta()
.use(htu21d, [options])  // where [options] define operational paramters -- omit to accept defaults
.listen(<port number>)   // where <port number> is the port on which the zetta server should listen

[options]

These options are defined in a file named 'options.json' which may be overridden by program definitions

"bus":"<i2c bus device>"
/dev/i2c-0, /dev/i2c-1, /dev/i2c-2, etc...  Defaults to /dev/i2c-1

"chronPeriod":<period>
period in milliseconds for monitored isochronal data

"streamPeriod":<period>
period in milliseconds for streaming data

<port number>

Agilatech has definied the open port number 1107 as its standard default for IIOT (Industrial Internet Of Things) server application. In practice, most any port above 1024 may be used by other organizations.

Example

Using directly in the zetta server:

const zetta = require('zetta');
const htu_sensor = require('@agilatech/zetta-htu21d-linux-driver');
zetta().use(htu_sensor).listen(1107);

Initializes the htu21d driver on i2c bus /dev/i2c-1 with a data monitoring period of 60 seconds and streaming data every second

To override the options defined in the options.json file, supply them in an object in the use statement like this:

zetta().use(htu_sensor, { "bus":"/dev/i2c-1", "chronPeriod":30000, "streamPeriod":15000 });

Overrides the defaults to initialize the bus on /dev/i2c-1 with a data monitoring period of 30 seconds and streaming data every 1.5 seconds

Properties

All drivers contain the following 5 core properties:

  1. state : the current state of the device, containing either the value chron-on or chron-off to indicate whether the device is monitoring data isochronally (a predefinied uniform time period of device data query).
  2. active : a boolean value indicating whether of not the underlying hardware is operational and active.
  3. id : the unique id for this device. This device id is used to subscribe to this device streams.
  4. name : the given name for this device.
  5. type : the given type for this device, usually containing the category of either Sensor or Actuator.

Monitored Properties

In the chron-on state and active operation, the driver software for this device monitors two values in isochronal fashion with a period defined by chronPeriod:

  1. humidity - Relative Humidity RH% range from 0-100
  2. temperature - Tempereature in °C range from -40°C to +125°C

Streaming Properties

If the hardware is active, the driver software continuously streams two values with a frequency defined by streamPeriod. Note that a streamPeriod of 0 disables streaming.

  1. humidityStream
  2. temperatureStream

State

chron-off is the beginning state. The driver also enters this state after a transition 'stop-isochronal' command.
In this state, all monitored data values are set to 0, and no sensor readings are updated.

chron-on is the state after a transition 'start-isochronal' command. In this state, all monitored data values are updated every time period as specified by 'chronPeriod'.

Transitions

  1. start-isochronal : Sets the device state to chron-on and begins the periodic collection of sensor data. Property values are monitored, with a period defined by the 'chronPeriod' option (defaults to 60 sec).
  2. stop-isochronal : Sets the device state to chron-off and stops data collection for the monitored values.

Design

The driver is specific to the HTU21D humidity and temperature sensor manufactured by Measurement Specialties. It will output both relative humidity RH% as well as tempurature in degrees celsius. The humidity sensor has a 3% tolerance accuracy, measuring 0-100% RH. The temperature sensor is accurate to ±0.3°C within the range of 5-60°C, degrading to a max of ±1.6°C lower than 0°C and greater than 60°C, measuring -40 to +125 degrees C.

Hardware

  • Beaglebone Black
  • Beaglebone Green
  • Should also work on Raspberry Pi as well as other Linux SBC

Copyright

Copyright © 2016 Agilatech. All Rights Reserved.

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.

Install

npm i @agilatech/zetta-htu21d-linux-driver

DownloadsWeekly Downloads

0

Version

0.9.3

License

MIT

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