Can I use a single USB On-The-Go (OTG) connection for simultaneous host and device roles?

No, you cannot. A USB On-The-Go (OTG) connection allows a host to dynamically change its role using the same connector, but not to have both roles simultaneously.

The ideal solution is to have a microcontroller with two USB ports. For specific device classes, such as the CDC device class, you could consider adding fixed function IC USB-UART/I2C bridge devices (such as MCP2200) to your board, using your microcontroller's UART interface.

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