hid_int_ep_write error "Failed to write endpoint buffer 0x81"

RE: hid_int_ep_write error "Failed to write endpoint buffer 0x81"

emanuelefalli — Fri, 06 Feb 2026 11:02:14 GMT

As a note on this since I had the same issue, I first checked that CONFIG_USB_HID_POLL_INTERVAL_MS was set to 1 in the prj.conf. On top of it, It's always good to set up a semaphore that is released only on the previous usb transfer being set succesfully, before initiating a new one. The lack of speed in DMA transfer is due to some other limitation in the firmware which slows it down won't probably depend on the USB transfer speed.

RE: hid_int_ep_write error "Failed to write endpoint buffer 0x81"

Jimmy — Thu, 22 Dec 2022 03:50:50 GMT

If i wait, the speed is slow down. If i wait, the usb hid speed is slower then ble, it does not make sense.

How to speed up DMA transfers?

RE: hid_int_ep_write error "Failed to write endpoint buffer 0x81"

Sigurd — Wed, 21 Dec 2022 17:45:53 GMT

Hi,

Looks like you are getting the waring pritned from here:

https://github.com/nrfconnect/sdk-zephyr/blob/v3.2.99-ncs1/subsys/usb/device/usb_device.c#L1312

So it seem like you are getting EAGAIN from usb_dc_ep_write()

https://github.com/nrfconnect/sdk-zephyr/blob/v3.2.99-ncs1/drivers/usb/device/usb_dc_nrfx.c#L1656

There is a note here that says:

/* USBD driver does not allow scheduling multiple DMA transfers
* for one EP at a time. Next USB transfer on this endpoint can be
* triggered after the completion of previous one.
*/

So you will need to wait until the previously scheduled write completes.

RE: hid_int_ep_write error "Failed to write endpoint buffer 0x81"

Jimmy — Wed, 21 Dec 2022 14:07:37 GMT

Not work, i tryed 16,32,64,128.

RE: hid_int_ep_write error "Failed to write endpoint buffer 0x81"

Sigurd — Wed, 21 Dec 2022 13:25:35 GMT

Hi,

Try increasing the value of CONFIG_BT_HOGP_REPORTS_MAX