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Forum: USB
Topic: USB HID KEYBOARD (Search a Programmer)

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Message to Edit: HTML is ON UBB Code is OFF Smilies Legend	Originally posted by Tsuneo on 08-30-2007 03:41 AM <b>b-2) Class specific request</b> The HID spec describes the implementation about class specific requests in this appendix. Appendix C: Keyboard Implementation (HID1_11.pdf p62) According to this description, these requests are required for keyboard implementation. <pre><font size="2">- Get_Report( Input ) - send keycode array - Set_Report( Output ) - on/off LEDs - Get_Idle - return current report duration - Set_Idle - set the report duration</font></pre> In the interface descriptor, bootable option is selected bInterfaceSubClass: 0x01 (bootable) Then, these requests also have to be supported. <pre><font size="2">- Get_Protocol - return current protocol boot/report - Set_Protocol - switch the protocol</font></pre> You'll see detailed description of these request in the HID spec. 7.2 Class-Specific Requests (HID1_11.pdf p50) b-2-1) Get_Report( Input ) When Get_Report( Input ) arrives, send 'snapshot' of the INPUT report just at the moment. b-2-2) Set_Report( Output ) On/off the LEDs according to the Output byte. b-2-3) Set_Idle, Get_Idle Set_Idle determines the repetition duration to send INPUT reports over the interrupt IN endpoint. - When the MSB of wValue is 0, it sets the duration to infinite; the IN EP sends report just when the any key is made/released. - When the MSB of wValue is not 0, it sets the duration to the value, multiplied by 4 ms. The HID spec recommends 125 (500 ms) as the default duration for keyboard. Windows sets this duration to 0 (infinite) in its enumeration. MacOSX sets it to 9 (36 ms). Get_Idle returns current duration. b-2-4) Set_Protocol, Get_Protocol On PC starts up, BIOS enables attached keyboard and mouse, when these device supports 'Boot' option. In some implementation, the report format can be different on 'Boot' and usual 'Report' state. Set_Protocol switches the state between 'Boot' and 'Report'. The default after Set_Configuration is 'Report' state. In this implementation, the report format is the same between 'Boot' and 'Report'. Then, Set_Protocol switches just the state variable. Get_Protocol returns current protocol state. <b>b-3) Endpoint handler</b> Send INPUT report over the interrupt IN endpoint. The timing to send the report depends on the duration set by Set_Idle. - When the duration is 'infinite', send report just when the device detects any key change, either make or break. - When the duration is a valid value, send report in specified duration. SOF interrupt (1ms interval) gives a good timer to count the duration. In either duration, the endpoint handler is executed in the main loop, not in the endpoint interrupt. Tsuneo [EDIT] March 8, 2009 Boot/Report status is initialized to "Report" at Set_Configuration (or Set_Interface, if any) [This message has been edited by Tsuneo (edited March 07, 2009).]
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