2 Replies Latest reply on May 14, 2018 3:20 PM by brbac_1258976

    Wiced_bt_hidd HID descriptor size and report size

      We are using the CYBT-343026 Bluetooth module with Wiced Studio 6.1 in a Bluetooth HID Device.

       

      The HID report descriptor is combined with other SDP records and initialized by calling the function wiced_bt_sdp_db_init().  What is the maximum size of the of the data base array that can be passed to the  wiced_bt_sdp_db_init() function?

       

      What is the maximum size of an HID report that can be sent to the function wiced_bt_hid_send_data()?  There is a defined constant HID_DEV_MTU_SIZE set to 64.  Does this mean that the maximum size of an HID report is 64 bytes?

        • 1. Re: Wiced_bt_hidd HID descriptor size and report size

          The SDP DB can be of any size, there is no limitation to the size of the array passed to wiced_bt_sdp_db_init().

           

          Actually, there is no limitation to the size of the record data that is passed to wiced_bt_hid_send_data(). It makes use of the buffer pools that you pass to wiced_stack_init(). If you do not have large buffers that can hold this data, then you are going to get a WICED_BT_HIDD_ERR_NO_RESOURCES error.

          By the way, why do you want to send such a large report?

           

          The HID_DEV_MTU_SIZE corresponds to the l2cap MTU size.

           

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          • 2. Re: Wiced_bt_hidd HID descriptor size and report size

            The HID report descriptor and the HID report for supporting a normal mouse are small but we are working on a Bluetooth HID interface for a multi-touch display that needs to support more than 10 active touches.  For 13 active touches the HID report descriptor is 848 bytes which makes the BT SDP DB 1161 bytes long.  For 13 active touches we can connect to the host PC and send the touch events correctly.  For 14 active touches the HID report descriptor is 910 bytes which makes the BT SDP DB 1223 bytes long.  When the HID report descriptor is setup for 14 active touches, the Wiced modules fails to connect to the host PC.  I asked this question because I am not sure what is causing the Wiced module to fail to connect to the PC when the HID report descriptor is configured for 14 active touch events.