USB Host on STM32H755ZI-Q: CDC Class Not Detected for USB-to-TTL Device

[Akshay_S]

Hello ,

I am working with the STM32H755ZI-Q board and configuring it as a USB Host. I’ve successfully tested the USB Host functionality using standard USB devices such as a keyboard and a mouse, both of which are recognized correctly by the host.

However, when I connect a USB-to-TTL adapter to the host, it fails to detect or enumerate the device. There is no response or indication that a USB device has been connected.

I would appreciate any guidance or suggestions on the following:

Are USB-to-TTL adapters supported in USB Host mode by default?

Is there any specific configuration or class driver (e.g., CDC class) that I need to enable for this to work?

Has anyone successfully interfaced a USB-to-TTL device with STM32 USB Host?

This is the output I see on Tera Term after enabling the user log :

USBH Event Triggered
Event : Start
PID: 7523h

VID: 1a86h

Address (#1) assigned.

Manufacturer : N/A

Product : USB Serial

Enumeration done.

This device has only 1 configuration.

Default configuration set.

No registered class for this device.

What steps are required to enable CDC functionality when connecting a USB-to-TTL adapter to the STM32 USB Host?

[FBL]

Hi @Akshay_S 

> Are USB-to-TTL adapters supported in USB Host mode by default?

No, USB-to-TTL adapters are not supported by default unless the USB Host stack includes the appropriate USB CDC ACM. Did you check this this knowledge base article?