Electronic – DIY: hardware encrypted pendrive

The USB can either be in device mode or in OTG mode. You cannot have OTG on the same USB bus as a host like a computer.

Multiple OTG devices can switch between host & device mode using "HNP" (Host negotiation protocol) but you can't do that with a pure host.

You would need two separate USB busses - one between the PC and the PIC, and one between the PIC and the devices. I don't think there is any PIC device that has 2 distinct USB interfaces.

I would suggest using a second device along side the PIC32 to act as a USB device to connect to the PC, and use the PIC32's USB in OTG mode to talk to the devices. This other device could be as simple as a FTDI chip to talk to the PIC32 through RS232, or something more powerful like another PIC (maybe a PIC18 with USB support) so you can talk through other protocols like I²C or SPI.

Ok, I can disregard the sanity of this project. It is insane, by the way, with little or no practical value beyond "doing it"-- but that never stopped me before and it shouldn't stop you.

In my opinion, you need several things: A CPU, an FPGA, some SDRAM, and a USB interface. Cypress makes the EX USB FX3 that does 2 of the 4 things. It has an ARM 9 CPU and USB 3.0 interface. What it doesn't have is an SDRAM interface-- which is why you want an FPGA. The FPGA does both the SDRAM interface as well as the high-speed data interface to the USB3 logic.

What you absolutely do NOT want is for the CPU to do the bulk of the data transfer! A 100 MHz ARM 9 isn't going to be able to handle that kind of data throughput. For that matter, just about any 2 GHz CPU isn't going to be able to handle that amount of data either. The ARM9 is just there for the housekeeping, while the FPGA does the heavy-lifting.

The ideal FPGA for this project is a Xilinx Spartan-6. Relatively low-cost, easy to program, and has built-in hard cores for the DDR2 SDRAM interface.