BLE Input/Output Maximum HID Report Size

RE: BLE Input/Output Maximum HID Report Size

terrorants — Thu, 10 Oct 2024 05:10:22 GMT

This seemed to do the trick. Thanks for the support!

RE: BLE Input/Output Maximum HID Report Size

Jørgen Holmefjord — Wed, 09 Oct 2024 12:12:50 GMT

Hi,

For HID over Bluetooth, the maximum length of an attribute value should be 512 octets (bytes), see this post.

I tried building the peripheral_hids_keyboard sample, and it seems that the default MTU length is set around the size where you stop receiving the packets.

CONFIG_BT_L2CAP_TX_MTU=65
CONFIG_BT_BUF_ACL_TX_SIZE=27
CONFIG_BT_BUF_ACL_RX_SIZE=69
CONFIG_BT_CTLR_DATA_LENGTH_MAX=69

Can you try to increase CONFIG_BT_L2CAP_TX_MTU and CONFIG_BT_BUF_ACL_RX_SIZE in your prj.conf file? Increasing CONFIG_BT_CTLR_DATA_LENGTH_MAX will also enable you to send more data in one packet (Increasing MTU will split data into multiple packets if data length cannot fit the full payload in one packet).

Best regards,
Jørgen

RE: BLE Input/Output Maximum HID Report Size

terrorants — Wed, 09 Oct 2024 04:07:16 GMT

Here's the relevant portion of the report descriptor:

    0x85, 0x02, /* Report ID */
    0x95, 0x3f,  /*   REPORT COUNT (63) */
    0x75, 0x08,        /*   REPORT_SIZE (8) */
    0x15, 0x00,        /*   LOGICAL_MINIMUM (0) */
    0x26, 0xff, 0x00,  /*   LOGICAL_MAXIMUM (255) */
	0x09, 0x01,        /*   USAGE (Vendor Usage 1) */
    0x81, 0x02,        /*   INPUT (Data,Var,Abs) */

    0x85, 0x02, /* Report ID */
    0x95, 0x3f,   /*   REPORT COUNT (63) */
    0x75, 0x08,        /*   REPORT_SIZE (8) */
    0x15, 0x00,        /*   LOGICAL_MINIMUM (0) */
    0x26, 0xff, 0x00,  /*   LOGICAL_MAXIMUM (255) */
	0x09, 0x01,        /*   USAGE (Vendor Usage 1) */
    0x91, 0x02,        /*   OUTPUT (Data,Var,Abs) */