The maxium length of buffer for USB HID SetReport

[CYH]

Hi,

I would like to know why when I sent the 202 bytes from pc to dev-board via USB HID, the buffer size would only get 32 byte each time, (byte[0]-byte[31])*several times until finished print out all 202 bytes?

Couldn't it recieved whole 202 bytes then print out continuously from byte[0] to byte[201]?

ux_device_keyboard.c

/**
  * @brief  USBD_HID_Keyboard_SetReport
  *         This function is invoked when the host sends a HID SET_REPORT
  *         to the application over Endpoint 0.
  * @PAram  hid_instance: Pointer to the hid class instance.
  * @PAram  hid_event: Pointer to structure of the hid event.
  * @retval status
  */
UINT USBD_HID_Keyboard_SetReport(UX_SLAVE_CLASS_HID *hid_instance,
                                 UX_SLAVE_CLASS_HID_EVENT *hid_event)
{
  UINT status = UX_SUCCESS;

  /* USER CODE BEGIN USBD_HID_Keyboard_SetReport */
  UX_PARAMETER_NOT_USED(hid_instance);
  UX_PARAMETER_NOT_USED(hid_event);

  //Receive Output report from PC
  if (hid_event == UX_NULL || hid_event->ux_device_class_hid_event_length < 2)
          return UX_ERROR;

      uint8_t report_id = hid_event->ux_device_class_hid_event_buffer[0];
      uint8_t *data = &hid_event->ux_device_class_hid_event_buffer[1];
      UINT data_len = hid_event->ux_device_class_hid_event_length - 1;

      if (report_id == 0x02 && data_len <= MAX_HID_OUTPUT_REPORT_SIZE)
      {
          // Copy the data to global buffer for later processing
          memcpy(g_output_report_buffer, data, data_len);
          g_output_report_length = data_len;
          g_output_report_ready = 1;
      }
  /* USER CODE END USBD_HID_Keyboard_SetReport */

  return status;
}

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And the desriptor alos has been changed like below:

__ALIGN_BEGIN uint8_t USBD_HID_KEYBOARD_ReportDesc[]
__ALIGN_END =
{
  /* USER CODE BEGIN USBD_HID_KEYBOARD_ReportDesc             */
  //Wedy Change for customized report
  0x06, 0x00, 0xFF,                   /* USAGE PAGE (HID Device)*/\
  0x09, 0xFF,                         /* USAGE (ASIC USAGE) */\
  0xa1, 0x01,                         /* COLLECTION (Application) */\
  0x15, 0x00,                         /*   LOGICAL_MINIMUM (0) */\
  0x25, 0xff,                         /*   LOGICAL_MAXIMUM (255) */\
  0x75, 0x08,                         /*   REPORT_SIZE (8) */\
  0x85, 0x01,                         /*   REPORT_ID (1). This defines input to the host side */\
  0x95, 0x10,                         /*   REPORT_COUNT (16) */\
  0x09, 0x01,                         /*   USAGE (ASIC USAGE) */\
  0x75, 0x08,                    /*     REPORT_SIZE (8)*/\
  0x81, 0x02,                         /*   INPUT (Data,Var,Abs) (note: output from host) */\
  0x85, 0x02,                         /*   REPORT_ID (2). This defines output from the host side */\
  0x95, 0xC9,                         /*   REPORT_COUNT (201) */\
  0x09, 0x01,                         /*   USAGE (ASIC USAGE) */\
  0x75, 0x08,                    /*     REPORT_SIZE (8)*/\
  0x91, 0x02,                         /*   OUTPUT (Data,Var,Abs) (note: input to host) */\
  /* USER CODE END USBD_HID_KEYBOARD_ReportDesc               */
  0xc0               /* End Collection                        */
};

[TDK]

USB FS packets are max 64 bytes in length. I assume the 32-byte packet size is some subset of those 64 bytes, probably HID-specific.

If you want them as a contiguous buffer, you'll have to reassemble them on the receiving side.

[CYH]

Hi Guru,

Thank you for the reply.

Do you know if I would like to modified the setting from .ioc file, which item I should modified? I would like to try to make the maxium be 64, as larger as it can.

[TDK · Accepted solution]

This is not something you can change.