Hello, I have a setup with ThreadX, NetX Duo and USBX. Implementing an CDC-ECM over USB2.0. The throughput we measure is rather low (at least not as expected with an USB2.0 480MBit/s).

[JCorn.3]

What options or tuning is possible to increase the throughput for this IP over USB?

Goal is to at least transfer 64KiB each 20ms or better. (22MBit/s or greater)

(started from project STM32H735G-DK/Applications/USBX/Ux_Device_CDC_ECM on github from

Kind regards,

Jan

[AScha.3]

you have a hi-speed phy connected ?

what is the throughput you get ?

[JCorn.3]

I use the STm32H753-eval2 and configured the USB OTG_HS (this board comes with an external hi-speed PHY).

The host computer shows the USB link as 480MBit/s.

The measurements I did shows that a 64KiB transfer takes 23.6 ms. (~22,2Mbit/s). (This is the transfer of the 64KiB buffer only. The TCP Connection setup is split off)

This throughput leaves me no headroom for my use-case.

For comparison: A transfer over wired Ethernet gives twice the throughput even at a link speed of 100Mbps. (16KiB → 3ms ==> ~44Mbps (wired ethernet is 100Mbps link))

Kind regards,

Jan

[BarryWhit]

480M is the signalling rate, not throughput. Additionally, USB "bulk" type transfers are limited by the spec to a theoretical max of 53MB/s (since bulk is "best-effort" and not allowed to take 100% of each frame). Older Cypress/Infineon  FX2LP appnotes have hard numbers for their demos, I don't recall exactly but I'm sure it's lower than 53MB/s. I don't have hard numbers for STM32.

Note that this upper bound is for "raw" endpoint communication. CDC-ECM has several software abstraction layers on top of that, so you should perhaps expect significantly less. I'm not sure.