View source for Unit USBHID

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=== Description ===
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'''Ultibo USB Human Interface Device (HID) Driver unit'''

The USB Human Interface Device (HID) class is one of the most widely used classes of USB devices. HID devices can appear as keyboard, mice, touch devices, gamepads, joysticks and many more.
 
Importantly HID devices can appear as controls within other devices, for example a USB headset can describe the volume and mute buttons as a HID device and a generic driver can recognize it without the need for a custom driver.
 
Unlike other USB devices where either an entire device or an interface on a device is used to provide a specific function, the HID standard allows multiple devices to coexist on the same interface. So a mouse and keyboard could be defined on a single USB interface and the HID implementation is able to route the reports they generate to the correct consumer.
 
Some HID devices (such as proprietary game devices) may require more specific handling than can be provided by the generic device infrastructure included in this unit.
 
In those cases a standard USB driver can be developed which claims the entire device by vendor and product (as USB offers the complete device to all drivers first). The driver can then configure the device as required and is able to use some of the services of both this unit and the HID unit to parse and examine the HID report descriptors.
 
Alternatively a HID consumer can be developed that claims the HID device during the optional HID DeviceBind callback which prevents other consumers from binding to the HID collections it contains. The consumer can then use some or all of the services of this unit and the HID unit to handle the HID report descriptors when dealing with reports received from the device.

=== Constants ===
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<div class="toccolours mw-collapsible mw-collapsed" style="border: 1; font-family: arial; padding-top: 20px; padding-bottom: 15px;">
<div style="font-size: 14px; padding-left: 12px;">'''USB HID specific constants''' <code> USB_HID_* </code></div>
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{| class="wikitable" style="font-size: 14px; background: white;"
|-
| <code>USB_HID_DRIVER_NAME = 'USB HID Driver';</code>
| Name of USB HID driver
|-
|}
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=== Type definitions ===
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'''USB HID request'''

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<code>PUSBHIDRequest = ^TUSBHIDRequest;</code>

<code>TUSBHIDRequest = record</code>
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{| class="wikitable" style="font-size: 14px; background: white;"
|-
| <code>Collection:PHIDCollection;</code>
| The collection this request corresponds to
|-
|}
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'''USB HID requests'''

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<code>PUSBHIDRequests = ^TUSBHIDRequests;</code>

<code>TUSBHIDRequests = array[0..0] of PUSBHIDRequest;</code>
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{| class="wikitable" style="font-size: 14px; background: white;"
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| &nbsp;
| style="width: 50%;"|&nbsp;
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|}
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'''USB HID device'''

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<code>PUSBHIDDevice = ^TUSBHIDDevice;</code>

<code>TUSBHIDDevice = record</code>
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{| class="wikitable" style="font-size: 14px; background: white;"
|-
|colspan="2"|''HID Properties''
|-
| <code>HID:THIDDevice;</code>
| The HID entry for this USB Device
|-
|colspan="2"|''USB Properties''
|-
| <code>USBDevice:PUSBDevice;</code>
| The USB device
|-
| <code>USBInterface:PUSBInterface;</code>
| The USB interface
|-
| <code>HIDDescriptor:PHIDDescriptor;</code>
| The USB HID descriptor from the interface
|-
|colspan="2"|''Driver Properties''
|-
| <code>ReportActive:LongWord;</code>
| The number of currently active report requests
|-
| <code>ReportMaxId:LongWord;</code>
| The maximum report id number this device supports
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| <code>ReportMaxSize:LongWord;</code>
| The maximum report size in bytes this device sends
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| <code>ReportRequests:PUSBHIDRequests;</code>
| Active input report requests from consumers
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| <code>ReportEndpoint:PUSBEndpointDescriptor;</code>
| The USB endpoint for receiving input reports
|-
| <code>OutputEndpoint:PUSBEndpointDescriptor;</code>
| The USB endpoint for receiving ouput reports
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| <code>PendingCount:LongWord;</code>
| Number of USB requests pending for this HID device
|-
| <code>WaiterThread:TThreadId;</code>
| Thread waiting for pending requests to complete (for device detachment)
|-
|}
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=== Public variables ===
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''None defined''

=== Function declarations ===
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'''Initialization functions'''

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<pre style="border: 0; padding-bottom:0px;">procedure USBHIDInit;</pre>
<div style="font-size: 14px; padding-left: 12px;">'''Description:''' Initialize the USB HID unit and USB HID driver</div>
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{| class="wikitable" style="font-size: 14px; background: white;"
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! Note
| Called only during system startup
|-
|}
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'''USB HID helper functions'''

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<pre style="border: 0; padding-bottom:0px;">function USBHIDCheckDevice(Device:PUSBDevice):Boolean;</pre>
<div style="font-size: 14px; padding-left: 12px;">'''Description:''' Check if the supplied USB device is suitable for detection as a USB HID Device</div>
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{| class="wikitable" style="font-size: 14px; background: white;"
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! Device
| The USB device to check
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! Return
| True if the device is suitable or False if it is not
|-
|}
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<pre style="border: 0; padding-bottom:0px;">function USBHIDCheckInterface(Device:PUSBDevice; Interrface:PUSBInterface):Boolean;</pre>
<div style="font-size: 14px; padding-left: 12px;">'''Description:''' Check if the supplied USB device and interface are a USB HID Device</div>
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{| class="wikitable" style="font-size: 14px; background: white;"
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! Device
| The USB device to check
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! Interrface
| The USB interface to check
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! Return
| True if the device and interface are a USB HID or False if not
|-
|}
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<div class="toccolours mw-collapsible mw-collapsed" style="border: 1; font-family: arial; padding-top: 0px; padding-bottom: 15px;">
<pre style="border: 0; padding-bottom:0px;">function USBHIDGetHIDDescriptor(Device:PUSBDevice; Interrface:PUSBInterface; Descriptor:PHIDDescriptor):LongWord;</pre>
<div style="font-size: 14px; padding-left: 12px;">'''Description:''' Get the HID Descriptor for a USB device and interface</div>
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{| class="wikitable" style="font-size: 14px; background: white;"
|-
! Device
| The USB device to get the descriptor for
|-
! Descriptor
| Pointer to a USB HID Descriptor structure for the returned data
|-
! Return
| USB_STATUS_SUCCESS if completed or another USB error code on failure
|-
|}
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<div class="toccolours mw-collapsible mw-collapsed" style="border: 1; font-family: arial; padding-top: 0px; padding-bottom: 15px;">
<pre style="border: 0; padding-bottom:0px;">function USBHIDStatusToErrorCode(Status:LongWord):LongWord;</pre>
<div style="font-size: 14px; padding-left: 12px;">'''Description:''' Convert a USB_STATUS_* code to an ERROR_* code</div>
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{| class="wikitable" style="font-size: 14px; background: white;"
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! Note
| None documented
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|}
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<pre style="border: 0; padding-bottom:0px;">function USBHIDErrorCodeToUSBStatus(Error:LongWord):LongWord;</pre>
<div style="font-size: 14px; padding-left: 12px;">'''Description:''' Convert an ERROR_* code to a USB_STATUS_* code</div>
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{| class="wikitable" style="font-size: 14px; background: white;"
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! Note
| None documented
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|}
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