Thoughts about increasing CDC transfer speed.

[kwagyeman]

Related area

CDC Transfer Speed

Hardware specification

imxrt

Is your feature request related to a problem?

Hi, we currently use TinyUSB on the IMXRT for USB CDC.

One of the things I noticed with our USB sniffer with USB HS is that many packets are NACKed.

In the example above, each 1-2 poll is a NACK. This is wasting USB bandwidth. Ideally, we'd want to have the data ready for USB before it needs it.

However, there's very little time to setup the data buffer before the USB controller needs the next one. Like 400ns.

Any thoughts on how this could be improved? Right now we are getting a callback via USB-CDC to prepare the data and memcpy it into a buffer. If this callback were executed before the host needed the data then this would improve our bandwidth.

Not sure how this could be done.

Describe the solution you'd like

Just opening a discussion on how to improve this. We are not bottlenecked by it right now.

openmv/openmv#2261

I have checked existing issues, dicussion and documentation

• I confirm I have checked existing issues, dicussion and documentation.