RE: Wireless mouse / trackpad emulator using nRF52

matterama — Mon, 08 Aug 2016 16:19:42 GMT

Thanks Hakon. I swear i tried that last week, but it didn't work. Retrying it now after clearing all remnants of the BLE device info on the PC and the behavior is as you describe. Thank you!

RE: Wireless mouse / trackpad emulator using nRF52

Håkon Alseth — Mon, 08 Aug 2016 06:46:42 GMT

Hi,

Unfortunately, we do not have any examples showing this behavior straight out-of-the-box. You can use the ble_app_hids_mouse example to perform this. You will have to change the behavior of the application, and parts of the USB descriptor in order to send absolute coordinates.

The changes done in the X/Y pointer descriptor is fairly straight forward. There is a input field in the descriptor stating if the data is absolute or relative.

    // Report ID 2: Mouse motion
    0x85, 0x02,       //     Report Id 2
    0x09, 0x01,       //     Usage (Pointer)
    0xA1, 0x00,       //     Collection (Physical)
    0x75, 0x0C,       //         Report Size (12)
    0x95, 0x02,       //         Report Count (2)
    0x05, 0x01,       //         Usage Page (Generic Desktop)
    0x09, 0x30,       //             Usage (X)
    0x09, 0x31,       //             Usage (Y)
    0x16, 0x01, 0xF8, //             Logical maximum (2047)
    0x26, 0xFF, 0x07, //             Logical minimum (-2047)
    0x81, 0x06,       //             Input (Data, Variable, Relative)
    0xC0,             //     End Collection (Physical)
    0xC0,             // End Collection (Application)

If you change the "Input" to state absolute on REPORT_ID 2, and you can send X/Y movement (from -2048 to 2047):

      0x81, 0x02,       //             Input (Data, Variable, Absolute)

Cheers, Håkon