I have existing hardware running on a atmega328 chip that I need to transfer it's data to a 32u2 via pins pd0 and pd2 of the mega328. Reason for this is that I'm hijacking the usb line I use with v-usb on the mega328. I successfully wrote my own protocol (a common clock / data paradigm) but I was wondering if there was a way to misuse(?) the usart or use another method. I can successfully transfer 16 bytes around 700us as it is now and need to be under 1ms. The mega328 runs a 12Mhz and the 32u2 is running a 16Mhz. I can use any pins on the 32u2 but I'm locked to the two pins on the mega328.
Thoughts? If not ill stick to what I have.