How to write data to a CDC Serial Device from ESP32-S3 Host?

[SunboX]

Hi,

I have a ESP32‑S3 DevKitC‑1 (N16R8). If I connect a Serial USB Device to the Host USB port of the ESP32, it is recognized and I'm getting VID/PID.
How can I now write to the Serial USB Device connected? Is there sample code somewhere?

greetings and thanks,
André

[tore-espressif]

Is this the example you are looking for? https://github.com/espressif/esp-idf/blob/master/examples/peripherals/usb/host/cdc/cdc_acm_host/main/usb_cdc_example_main.c#L150

[SunboX]

Maybe, kind of, yes ... but, I was looking for a TinyUSB example. ;)

[hathach]

check out the host/cdc_msc_hid example https://github.com/hathach/tinyusb/blob/master/examples/host/cdc_msc_hid/src/cdc_app.c

[SunboX]

I got it working by using a “CH34x VCP shim” because the FS‑600 used in this project here https://github.com/SunboX/radpro-wifi-bridge exposes its USB UART as a vendor‑specific interface (0xFF/0x01/0x02) instead of proper CDC-ACM descriptors. TinyUSB’s host stack only binds its CDC driver when it sees the full Communication/Data interface pair plus the CDC functional descriptors. So when the CH34x shows up, TinyUSB shrugs and leaves the interface untouched. The shim steps in to claim those VID/PID combos, synthesise the CDC bits TinyUSB expects, and stub out control requests (like SET_LINE_CODING) that the CH34x ignores anyway.

To make this unnecessary, TinyUSB would need upstream support for CH34x-style VCPs. Either the existing CDC host driver gains quirk hooks for VID/PID/class 0xFF, skipping the strict descriptor checks and tolerating missing line-control features, or TinyUSB ships a dedicated CH34x host driver that plugs into the stack and exposes the same API as CDC. Once TinyUSB handles that internally, projects like mine could drop the shim and rely on the stock host driver.

[SunboX]

Thanks again! I removed the shim and rewrote my code a bit. Seems to work. :)

[SunboX]

Ok, I have to revert back ... it seems not to work. All USB messages time out now. Even if I remove CFG_TUH_CDC_CH34X_VID_PID_LIST. There's smth wrong now. Have to investigate further, reverted the changes for now to get it back to a working state. All changes are still in branch https://github.com/SunboX/radpro-wifi-bridge/tree/tinyusb-simplify

[SunboX]

Somehow it seems it does not do the handshake after the device is powered on. Is there some minimal CH34X CDC Host Example preferable for the ESP32-S3 that I can try together with my Bosean FS-600 running RadPro 3.0.1 ? Just to rule out that the issues lies on my side?

[hathach]

check my above comment for the stock example

[SunboX]

ah, sry. Missed that. I take a look