HID Device
Review the following information for setting up and configuring the HID Device driver.
Introduction
Human Interface Devices (HID), USB-connected peripheral devices such as scanners (generally for barcodes or QR codes), can be polled for data.
Litmus Edge Compatible Series
Compatibility parameter | Compatible items |
|---|---|
Driver type | Serial |
Validated devices/series | Human Interface Devices. Examples include scanners used for barcodes and QR codes. |
To set up and configure this device in Litmus Edge, you will need to do the following:
- Step 1: Set up and Configure the PLC Device
- Step 2: Set up the PLC Device in Litmus Edge DeviceHub
- Step 3: Configure the List of Registers
Step 1: Set up and Configure the PLC Device
Record the serial communication parameters for the device. Otherwise, use PLC software on your machine to look up these parameters. You use these parameters for setting up the driver in the next step.
Step 2: Set up the PLC Device in Litmus Edge DeviceHub
Configure the following parameters when you Connect a Device with this driver. Update default values to the specific setup of your device.
Parameter | Value |
|---|---|
Type | HID Devices |
Driver | HID Device |
Communication Port | Local Serial connection file path |
Step 3: Configure the List of Registers
In the context of Litmus Edge, the following characteristics are relevant for this serial device:
- The HID remains disconnected because HIDs send data only when there is data to send.
- Only one tag is required in order to read the data. Only one register name and data type are available to select. Use this one name and data type to connect to the HID device.
- The tag supports only ASCII characters.
- By default, the polling interval is set to 1. You cannot change this default value in Litmus Edge. The actual interval is defined by the device's publishing rate.
- Data can be collected onto flows when it is scanned.
Refer to the following tag parameters.
Tag Parameters
- Name: Select R.
- Value Type: Select raw.
- Polling Interval: Enter a value in seconds.
- Tag Name: Enter a name.
- Description (Optional): Enter a description for the tag.
- Tag Formula: Enter a formula for the tag to process the generated data. Two variables are permitted: value (current tag value) and timestamp (current tag UNIX time in milliseconds). The following math functions are available:
- sin
- cos
- sqrt
- tan
- power: power(x) performs the operation 10^x.
- log: log(x) is the natural logarithm (the logarithm is in base e).
- exp: exp(x) performs the operation e^x.
- Only Publish on Change of Value: Select the checkbox to customize NATS messages to be published only when the value parameter changes from a previous value to a new one. Change of Value only applies to boolean, numeric (such as int or float), and simple string data types. It does not apply to complex types, such as JSON or array. Poll-once topics will not be affected by Change of Value settings. These topics will still only see a single message.
- Meta Data: Metadata summarizes basic information about data. This feature allows you to define key-value pair data for the device output payload later on. It can then be used to find, use, and reuse particular instances of data.
Note: If you use special characters in meta data key names, the special characters are replaced with underscore characters in the payload. This can cause two key names to be combined into one. For example, configuring the key names a**b and a&&b will cause only one key name to be created (a__b).