Thanks for the feedback!

I was thinking some more about the tradeoffs between implementing the low level endpoint API vs high level serial API, and I changed my mind and am leaning more towards the EndpointStream for a few reasons:

• An API that dynamically allocates a fifo for reading from an endpoint would support infinite endpoints. However, with TinyUSB's CDC class, the number of USB communication ports supported on the host depends onCFG_TUH_CDC. You can increase it to deal with devices that spawn many CDC ports, but this comes at the expense of memory.
• EndpointStream solves non-blocking USB for any device, not just serial. This might be useful forkeyboards,midi, etc. The pyserial-compatible API could be provided by a Python module wrapping the EndpointStream.
• It requires fewer functions to implement.

Curious to hear your thoughts. I can close this and open a new PR.

It's up to you what you'd like to implement.

I'd lean against EndpointStream because it'd be a new unique API. This higher level has the advantage of matching the existing pyserial api. The low level core APIs match pyusb in CPython.

Is there a pyusb version of EndpointStream?

Good point. There's nothing existing, and it seems pyusb is blocking only. You'd need to use threads to do USB communication in the background. There is a PR to pyusb to make it async and add asubmit_read/submit_write that returnasyncio.Future objects, but it's not very far along. It seems by far the simplest and more Pythonic, but from my understanding there's very few modules in CircuitPython leveraging asyncio, so maybe it's not a good fit here.

I can continue to work on the pyserial approach.

Thanks! I think pyserial is best. It feels like the defacto way to do host serial.

Worth looking at#9365 and#10019. pyserial has some idiosyncrasies in its API which are not the greatest, so I ended up doing something slightly different forusb_cdc.

Forgive me if this is a silly question, but does this enable USB Host support, or does it still require theusb_host module?

Forgive me if this is a silly question, but does this enable USB Host support, or does it still require theusb_host module?

This PR is about adding better support for USB serial devices when they are connected to the USB host port of a CircuitPython board with USB host capability. The existing way of doing USB host stuff is to use theusb module, which mostly follows the PyUSB API. There are also some higher level CircuitPython helper modules that make it easier to use keyboards, mice, gamepads, and such.

Despite the name which suggests otherwise, theusb_host module is mostly not important for interacting with USB host devices in CircuitPython. Its purpose is for changing USB host settings that usually don't need to be changed.

If you want to learn about writing CircuitPython code for USB host stuff, the best places to ask questions are theAdafruit Forums or the#help-with-circuitPython channel onAdafruit's Discord. You could also search for "USB host" on theAdafruit Learning System or theAdafruit Playground.

Thank you for the response! I've asked on the Discord and hopefully I'll get a response. I won't derail the thread here, but essentially I'm trying to use a Seeed XIAO ESP32S3 as a USB host to connect to a device that uses serial communication. And I'm having a horrible time trying to figure out how to do it (every time I try to dousb.core.find(find_all=True), I getRuntimeError: No usb host port initialized).

Something like you've proposed here would probably make my life much easier once I can actually communicate with the device :)