HID USAGES
HID devices send data in reports. Elements of data in a report are identified by unique identifiers called usages. The structure of the device’s reports and the device’s capabilities are reported to the host in a report descriptor. The host usually gets the report descriptor only once, right after the device is plugged in. The report descriptor usages identify the devices capabilities and report structures. For example, a device could be identified as a keyboard by analyzing the device’s report descriptor. Usages are four byte integers. The most significant two bytes are called the usage page and the least significant two bytes are called usage IDs. Usages that are related can share a common usage page. Usages can be standardized or they can be vendor defined. Standardized usages such as usages for mice and keyboards can be found in the HID Usage Tables document and can be downloaded free at www.usb.org. Vendor defined usages must have a usage page in the range 0xff00 – 0xffff. All usages for this device use vendor defined relay controller usage page 0xff00.
The usage IDs for this device are defined in the following table. The usage types are also listed. These usage types are defined in the HID Usage Tables document.
Relay Controller usage page 0xff00:
| Usage ID | Usage Name | Usage Type | Report Type |
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| (Hex) |
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| 1 |
| Relay Controller device | Collection |
| None |
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| 1 |
| Status | Data |
| Input |
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| 2 |
| Operational commands | Data |
| Output |
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| 3 |
| Configuration message | Data |
| Feature |
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REPORT DESCRIPTOR |
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The HID report descriptor is structured as follows: |
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| Item |
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| Value (Hex) | ||
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| Usage Page (Relay Controller) |
| 06 00 FF | |||
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| Usage (Relay Controller device) |
| 09 01 |
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| Collection (Application) |
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| A1 01 | ||
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| Globals |
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| Logical Minimum (0) |
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| 15 00 |
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| Logical Maximum (255) |
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| 26 FF 00 | |
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| Report Size (8) |
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| 75 08 |
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| Input Report |
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| Usage (Status) |
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| 09 01 |
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| Report Count (8) |
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| 95 08 |
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| Input (Data, Variable, Absolute, Bitfield) |
| 81 02 |
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