Gpio input/output device driver for use in the Agilatech Lynxari system
npm install @agilatech/lynxari-gpio-device!Lynxari IoT Platform IoT Platform
This device driver is specifically designed to be used with the Agilatech® Lynxari IoT Platform.
Please see agilatech.com to download a copy of the system.
$> npm install @agilatech/lynxari-gpio-device
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This device driver is designed to control a single GPIO input/output. The device must be designated as either an output OR an input. If it is an output, it can be set to high or low. If it is an input, the driver will publish a new value immediately upon being triggered, and it may also be triggered via software. No assumptions are made as to the end use of the output, be it lighting an LED or controlling the coolant valves on a nuclear power plant. Therefore, it is up to the end user application to decide upon latency and frequency issues.
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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 with Lynxari, insert its object definition as an element in the devices array in the _devlist.json_ file.
{
"name": "GPIO",
"module": "@agilatech/lynxari-gpio-device",
"options": {
"devicePoll": 1000,
"streamPeriod": 60000
}
}
#### Device config object
The device config object is an element in the devlist.json device configuration file, which is located in the Lynxari root directory. It is used to tell the Lynxari system to load the device, as well as several operational parameters.
_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 within the device config object which defines all other operational parameters. In general, any parameters may be defined in this options object, and most modules will have many several. The three which are a part of every Lynxari device are 'devicePoll', 'streamPeriod', and 'deltaPercent'. The gpio options also can define gpio, direction, edge, and debounce.
"devicePoll":
Period in milliseconds in which device will be polled"streamPeriod":
Period in milliseconds for broadcast of streaming values
"gpio":
The GPIO pin or other definition, where the system can connect to the I/O
"direction":
Direction is either "in" for inputs or "out" for outputs. Defaults to "out".
"edge":
Trigger edge can be one of "rising", "falling", "both", or "none". Defaults to "none".
"debounce":
Defines a time after which further inputs are ignored. Used to debounce a mechanical switch. Defaults to 10.
#### gpio is a manatory config parameter
Either in the .use statement or the config.json file, gpio must be defined to be the valid gpio pin number of the input or output. Note that this number may not be the same as the physical connector pin number on the board.
#### direction defines whether it is an input or an output
If direction is "in", then the device is expecting to be switched or triggered by some external event. If the direction is "out", then the device will output a high or a low to the pin.
#### edge is applicable only to input
Trigger inputs have a rising (leading) and falling (trailing) edge. This option defines which edge will cause the input event to be raised. If "both", then an event will be raised on the rising and falling edges.
#### debounce eliminates switch bounce
All mechanical switches display some "bounce" where the signal will briefly fluctuate as it is switched. This bounce usually lasts for only a few milliseconds, but every switch is different. For that reason, this option ignores any further level changes for the time period after the initial trigger. The time period is in milliseconds, and has no upper limit.
#### streamPeriod and devicePoll
These options have little applicability for an input/output device such as this. Since this device only updates the
level property when commanded to do so, 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 level parameter will be updated when it is changed.
#### module config
Every module released by Agilatech includes configuration in a file named 'config.json' and we encourage any other publishers to follow the same pattern. 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 puts the device on pin 2, disables streaming, and polls the device every hour:
{
"gpio":2,
"streamPeriod":0,
"devicePoll":3600000
}
#### Default values
If not specified in the config object, the program uses the following default values:
* _name_ : GPIO
* _direction_ : out
* _edge_: none
* _debounce_ : 10
* _streamPeriod_ : 10000 (10,000ms or 10 seconds)
* _devicePoll_ : 1000 (1,000ms or 1 second)
#### Monitored Properties
In the on state, the driver software for this device monitors one value.
1. level - the current level of the output, either 'high' or 'low'
#### Streaming Properties
For this gpio 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.
1. level_stream
2. 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.
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