Availability machine.USBDevice on stm32

[saraverbeecke]

Are there plans to make the USBDevice class available on the stm32 platforms?
If needed, I would like to contribute but I am not a specialist in USB stuff. Is it easy to port from the rp2040 code to the stm32?

[andrewleech]

The machine.USBDevice API is built on top of the TinyUSB library, whereas the stm32 port currently uses stm's native USB stack.

I've been working towards migrating stm32 over to TinyUSB in #15592 in my personal time, once that's finished the runtime USB support should just work.

Before I can finish that though, the stm32 port has some other more advanced USB features like the CDC / VCP interface being exposed to python with the default repl being configured via dupterm. This provides the ability at runtime to disconnect the USB CDC from repl and use it for custom data.
I'm working towards implementing this functionality for all TinyUSB based ports in #16017

Once that's in I can finish migrating stm32 to TinyUSB without losing the existing features.

[andrewleech]

The usbhost support isn't in a PR yet, needs a lot of cleaning up first. Currently it's just exposing the host drivers built into tinyusb; I don't know if they have host support for midi built in. Once this initial support is finished and working it should be possible to extend it to provide a runtime / python definition interface for custom drivers like USBDevice has but I'm not sure how much work that'll be.

[saraverbeecke]

@andrewleech what do I need to add in my mpconfigboard.h if I want to test your tinyusb implementation on my stm32h7 (REPL over USB and MSC support for example?)
I added:

#define MICROPY_HW_TINYUSB_STACK 1
#define MICROPY_HW_ENABLE_USBDEV 1
#define MICROPY_HW_USB_CDC 1

but I cannot see the USB device in my devices list after a successful build and deployment.

[andrewleech]

Is this with the current version of my PR checked out?
I would have expected just #define MICROPY_HW_TINYUSB_STACK 1 should be all it takes.
That should get USB CDC for repl; mass storage isn't supported currently.

Maybe there's an issue with the h7, I'll have to see if I can find a high speed USB device to test with.

[saraverbeecke]

No need to test anymore, I forgot to add first #define MICROPY_HW_ENABLE_USB 1. I thought the #define MICROPY_HW_TINYUSB_STACK 1 did this by default.
So I have REPL over USB working now with:

#define MICROPY_HW_ENABLE_USB 1
#define MICROPY_HW_TINYUSB_STACK 1

(yes, tested with your version of the PR checked out.)
Is it straight forward to add MSC here?

[andrewleech]

I don't know how much effort MSC would be, I hate it on embedded devices because it pretty much always results in corrupted flash.
I know it can be enabled in TinyUSB but then it'd need binding code to get from that to the raw flash block layer.
I and a couple of others have been slowly working on a USB MTP driver which is the much safer replacement for MSC, hopefully that can be finished off soon.