Mouse HID Descriptor for more than 3 mouse buttons

Official Hardware Classic Leonardo
1

I need to support more than 3 mouse buttons via the built-in Mouse HID for the Arduino Leonardo. I've taken the Mouse.cpp/h files and modified them to set the descriptor as follows:

static const uint8_t _hidReportDescriptor[] PROGMEM = {
  
  //  Mouse
    0x05, 0x01,                    // USAGE_PAGE (Generic Desktop)  // 54
    0x09, 0x02,                    // USAGE (Mouse)
    0xa1, 0x01,                    // COLLECTION (Application)
    0x09, 0x01,                    //   USAGE (Pointer)
    0xa1, 0x00,                    //   COLLECTION (Physical)
    0x85, 0x01,                    //     REPORT_ID (1)
    0x05, 0x09,                    //     USAGE_PAGE (Button)
    0x19, 0x01,                    //     USAGE_MINIMUM (Button 1)
    0x29, 0x05,                    //     USAGE_MAXIMUM (Button 5 )
    0x15, 0x00,                    //     LOGICAL_MINIMUM (0)
    0x25, 0x01,                    //     LOGICAL_MAXIMUM (1)
    0x95, 0x05,                    //     REPORT_COUNT (5)
    0x75, 0x01,                    //     REPORT_SIZE (1)
    0x81, 0x02,                    //     INPUT (Data,Var,Abs)
    0x95, 0x01,                    //     REPORT_COUNT (1)
    0x75, 0x05,                    //     REPORT_SIZE (5)
    0x81, 0x03,                    //     INPUT (Cnst,Var,Abs)
    0x05, 0x01,                    //     USAGE_PAGE (Generic Desktop)
    0x09, 0x30,                    //     USAGE (X)
    0x09, 0x31,                    //     USAGE (Y)
    0x09, 0x38,                    //     USAGE (Wheel)
    0x15, 0x81,                    //     LOGICAL_MINIMUM (-127)
    0x25, 0x7f,                    //     LOGICAL_MAXIMUM (127)
    0x75, 0x08,                    //     REPORT_SIZE (8)
    0x95, 0x03,                    //     REPORT_COUNT (3)
    0x81, 0x06,                    //     INPUT (Data,Var,Rel)
    0xc0,                          //   END_COLLECTION
    0xc0,                          // END_COLLECTION
};

Someone else had posted this descriptor and another person claimed it worked. However, when I do this, the Mouse functionality stops working. I'm wondering if something with the packet that has to be sent changes with this new descriptor. The value being sent should support up to 8 buttons as it's a 4 byte packet being sent with SendReport.

Anyone else have luck supporting buttons 4-8 using the Leonardo?

Thank you

2

I was able to solve this with the help of: https://eleccelerator.com/tutorial-about-usb-hid-report-descriptors/

The issue was the following entries

    0x95, 0x01,                    //     REPORT_COUNT (1)
    0x75, 0x05,                    //     REPORT_SIZE (5)

The 5 here represents padding, so if we want to support 8 buttons, this has to be 0 or the two entries removed all together.

This is how I was able to support 8 buttons:

static const uint8_t _hidReportDescriptor[] PROGMEM = {
  
  //  Mouse
    0x05, 0x01,                    // USAGE_PAGE (Generic Desktop)  // 54
    0x09, 0x02,                    // USAGE (Mouse)
    0xa1, 0x01,                    // COLLECTION (Application)
    0x09, 0x01,                    //   USAGE (Pointer)
    0xa1, 0x00,                    //   COLLECTION (Physical)
    0x85, 0x01,                    //     REPORT_ID (1)
    0x05, 0x09,                    //     USAGE_PAGE (Button)
    0x19, 0x01,                    //     USAGE_MINIMUM (Button 1)
    0x29, 0x08,                    //     USAGE_MAXIMUM (Button 5 )
    0x15, 0x00,                    //     LOGICAL_MINIMUM (0)
    0x25, 0x01,                    //     LOGICAL_MAXIMUM (1)
    0x95, 0x08,                    //     REPORT_COUNT (5)
    0x75, 0x01,                    //     REPORT_SIZE (1)
    0x81, 0x02,                    //     INPUT (Data,Var,Abs)
    0x95, 0x01,                    //     REPORT_COUNT (1)
    0x75, 0x00,                    //     REPORT_SIZE (5)
    0x81, 0x03,                    //     INPUT (Cnst,Var,Abs)
    0x05, 0x01,                    //     USAGE_PAGE (Generic Desktop)
    0x09, 0x30,                    //     USAGE (X)
    0x09, 0x31,                    //     USAGE (Y)
    0x09, 0x38,                    //     USAGE (Wheel)
    0x15, 0x81,                    //     LOGICAL_MINIMUM (-127)
    0x25, 0x7f,                    //     LOGICAL_MAXIMUM (127)
    0x75, 0x08,                    //     REPORT_SIZE (8)
    0x95, 0x03,                    //     REPORT_COUNT (3)
    0x81, 0x06,                    //     INPUT (Data,Var,Rel)
    0xc0,                          //   END_COLLECTION
    0xc0,                          // END_COLLECTION
};