I have an legacy uninterruptible power supply (UPS) that communicates to a host over USB. The commands are proprietary. The UPS is now obsolete and will be replaced with a new UPS. The new UPS still connects to the host over USB; however, it uses different commands. The design of the host is locked (can't touch it) so I am tasked to design a piece of hardware that sits between the host and the new UPS. I am thinking STM32F2 since it supposedly can do both host and device USB at the same time. Can anyone give me an idea of where to start on this project? Any input would be appreciated.