USB between two MCUs & host PC
I am looking to design a split keyboard that requires USB communication between two keyboard halves and a host computer. The left half will have a USB-C connection to a host computer and appear as a USB HID with regular keyboard functionality. This connection will also source power from the host.
The left half will also have a USB-C connection to the right keyboard half providing power to the right.
The right half will have a USB-C connection to the left half and must source power from the left half.
Keeping cost low is critical so the USB-C connection between the halves would not need to use standard USB-C communication and could implement a USB alternate mode as per the USB-C specification and then use UART between the MCUs.
The STM32G0B1xB/xC/xE series have two USB Type-C Power Delivery controllers available. Would I be able to use UCPD1 on the left half PCB to negotiate power delivery from the host computer and establish a USB 2.0 connection to the host. Then use the UCPD2 to connect to the right half PCB and establish an alternate mode using UART on the SBU1&SBU2 pins, with the left half sourcing power and the right sinking power.
All USB-C connections would need to be USB compliant.