Posted on September 29, 2016 at 14:22
The keys are assigned to bits on the input report one by one.
For example,
Hi Alex,
> Now I'm struggling to make multimedia keys work. 'Multimedia' keys belong to HID consumer device, apart from other keys (HID keyboard). - To send these keys, you have to modify your report descriptor completely for HID consumer device. - If you would like to have 'multimedia' keys with ordinary keys, you should make a composite device, HID keyboard + HID consumer, because Windows don't like merged keyboard with other HID device(s) using TLCs (Top-Level Collections). In this reason, all of PC keyboards are composite devices. The support of 'multimedia' keys depend on OS. Windows support is described on keyboard-support-windows-8.docx, downloaded from this MS page,https://msdn.microsoft.com/en-us/library/windows/hardware/Dn613956%28v=vs.85%aspx
The keys are assigned to bits on the input report one by one.
For example,
//
// Report descriptor for media remote controller
//
// This descriptor defines ONE byte report, of this bitmap
// bit
// 0 : Next
// 1 : Previous
// 2 : Stop
// 3 : Play/Pause
// 4 : Mute
// 5 : Volume Up
// 6 : Volume Down
// 7 : --- (padding)
//
static u8 usbHidReportDescriptor[39] = { /* USB report descriptor */
0x05, 0x0c, // USAGE_PAGE (Consumer Devices)
0x09, 0x01, // USAGE (Consumer Control)
0xa1, 0x01, // COLLECTION (Application)
// -------------------- common global items
0x15, 0x00, // LOGICAL_MINIMUM (0)
0x25, 0x01, // LOGICAL_MAXIMUM (1)
0x75, 0x01, // REPORT_SIZE (1) - each field occupies 1 bit
// -------------------- misc bits
0x95, 0x05, // REPORT_COUNT (5)
0x09, 0xb5, // USAGE (Scan Next Track)
0x09, 0xb6, // USAGE (Scan Previous Track)
0x09, 0xb7, // USAGE (Stop)
0x09, 0xcd, // USAGE (Play/Pause)
0x09, 0xe2, // USAGE (Mute)
0x81, 0x06, // INPUT (Data,Var,Rel) - relative inputs
// -------------------- volume up/down bits
0x95, 0x02, // REPORT_COUNT (2)
0x09, 0xe9, // USAGE (Volume Up)
0x09, 0xea, // USAGE (Volume Down)
0x81, 0x02, // INPUT (Data,Var,Abs) - absolute inputs
// -------------------- padding bit
0x95, 0x01, // REPORT_COUNT (1)
0x81, 0x01, // INPUT (Cnst,Ary,Abs)
0xc0 // END_COLLECTION
};