Lynxari Mock Sensor device driver
This device driver is specifically designed to be used with the Agilatech® Lynxari IoT System. Please see agilatech.com to download a copy of the system.
Install
$> npm install lynxari-mock-device
Install in the same directory in which lynxari is installed.
Design
This device driver is designed to simulate a general sensor device. It does this by supplying a random float periodically which acts like a sensor parameter.
Usage
This device driver is designed to be consumed by the Agilatech® Lynxari IoT system. As such, it is not really applicable or useful in other environments.
To use it in Lynxari, insert its object definition as an element in the devices array in the devlist.json file.
{
"name": "MOCK",
"module": "@agilatech/lynxari-mock-device",
"options": {
"devicePoll": 60000,
"streamPeriod": 0
}
}
Device config object
The device config object is an element in the devlist.json device configuration file. It is used to tell the Lynxari system to load the device, as well as several operational parameters. The mock device is simple enough to use a minimal configuration, but most real-world drivers will be have more complex config objects.
name is simply the name given to the device. This name can be used in queries and for other identifcation purposes.
module is the name of the npm module. The module is expected to exist in this directory under the node_modules directory. If the module is not strictly an npm module, it must still be found under the node_modules directory.
options is an object which defines all other operational parameters. In general, any parameters may be defined in this object, and most modules will have many several. The three which are a part of every Lynxari device are 'devicePoll', 'streamPeriod', and 'deltaPercent'. Finally, the value paramter can have a range defined by specifying 'value_range'.
"devicePoll":<period>
Period in milliseconds in which device will be polled
"streamPeriod":<period>
Period in milliseconds for broadcast of streaming values
"deltaPercent":<percent>
Percent of the data range which must be exceeded (delta) to qualify as "new" data
devicePoll and streamPeriod
devicePoll is given in milliseconds, and defines how often the device will be polled for new values. This paramter is primary useful in sensors which sit idle waiting to be polled, and not for devices which supply values on their own schedule (i.e. for pull ranther that push).
streamPeriod is also given in milliseconds, but is disabled if set to 0.
These config options have little applicability for an event-based sensor such as this. Since this mock sensor simply updates (pushes) the monitored variable periodically, it makes little sense to stream the value or poll the device for a new value. Because of this, it is advisable to set streamPeriod to 0, which disables streaming, and set the devicePoll to some arbitrarily large value. Regardless of the setting of these config, the value will be updated as generated periodically.
deltaPercent explained
deltaPercent is the percentage of the current numerical data range which a polled data value must exceed to be considred "new". As an example, consider a temperature range of 100, a deltaPercent of 2, and the current temerature of 34. In such a case, a device poll must produce a value of 36 or greater, or 32 or less than in order to be stored as a current value. 35 or 33 will be ignored. deltaPercent may be any value greater than 0 or less than 100, and may be fractional. If not defined, the default is 5 percent.
Defining the value ranges
Value ranges may also be defined in the options, and are closely related to deltaPercent. If not defined, the software will keep track of minimum and maximum values and derive the range from them. However, that takes time for the software to "learn" the ranges, so they can be defined in the options object:
"value_range":<numeric range>
where the <numeric range> is a number representing the absolute range of the value.
module config
Every module released by Agilatech includes configuration in a file named 'config.json' and we encourage any other publishers to also do the same. The parameters in this file are considered defaults, since they are overriden by definitions appearing in the options object of the Lynxari devlist.json file.
The construction of the config.json mirrors that of the options object, which is simply a JSON object with key/value pairs. Here is an example of an 'config.json' file which polls the device every hour and streams values every two hours:
{
"devicePoll":3600000,
"streamPeriod":7200000,
}
Default values
If not specified in either the devlist.json or the config.json files, the program uses the following default values:
- streamPeriod : 10000 (10,000ms or 10 seconds)
- devicePoll : 1000 (1,000ms or 1 second)
- deltaPercent : 5 (polled values must exceed the range by ± 5%)
Properties
All drivers contain the following 4 core properties:
- 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).
- id : the unique id for this device. This device id is used to subscribe to this device streams.
- name : the given name for this device.
- type : the given type category for this device, (sensor, actuator, etc)
Monitored Properties
In the on state, the driver software monitors all values. Since the mock device only has one value, only one is monitored.
- value - The value is a random float between 0.0 and 99.9
Streaming Properties
For this mock device, it is usual to disable streaming. However, if it is not disabled, while in the on state, the driver software continuously streams this value in isochronal fashion with a period defined by streamPeriod. Note that a streamPeriod of 0 disables streaming.
- value_stream
State
This device driver has a binary state: on or off. When off, no parameter values are streamed or available, and no commands are accepted other than the turn-on transition. When on, the device is operations and accepts all commands. The initial state is off.
Transitions
-
turn-on : Sets the device state to on. When on, the device is operational and accepts all commands. Values are streamed, and the device is polled periodically to keep monitored values up to date.
-
turn-off : Sets the device state to off, When off, no parameter values are streamed or available, and no commands are accepted other than the turn-on transition.
Compatibility
This driver is designed to run within the Lynxari IoT platform. Lynxari will run on the following operating systems:
- 32 or 64-bit Linux
- Windows 7 and up
- macOS and OS X
- SunOS
- AIX
Copyright
Copyright © 2018 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.