RE: nRF52840 USB CDC strange problem on Windows 10

Juan — Fri, 04 Jan 2019 09:19:16 GMT

Ok, thanks! that makes sense for me now.

RE: nRF52840 USB CDC strange problem on Windows 10

Turbo J — Thu, 03 Jan 2019 18:15:36 GMT

[quote userid="76200" url="~/f/nordic-q-a/42120/nrf52840-usb-cdc-strange-problem-on-windows-10"]In theory, everything is working as expected, but the problem I see on Windows 10 is that Windows does not receive any data until I send 4096 bytes. [/quote]

That is actually expected behaviour for USB bulk endpoints, and stated as such in the USB 2.0 spec.

In order to receive less than 4096 bytes, the last packet must be smaller than 64 bytes. USB also allows for zero byte packets, which can be used to send any integer multiple of 64 bytes as one transaction.

Note that most CDC example implementations omit this zero packet handling for simplicity.

[quote userid="76200" url="~/f/nordic-q-a/42120/nrf52840-usb-cdc-strange-problem-on-windows-10"]I tested the same code on a Raspberry pi and I am not having the same issue.[/quote]

Linux should behave roughly similar, but I have not tested USB CDC there much - was rather using LibUSB directly.