The IP core from opencores is only implemented in
function protocol,this is digital circuit. U also need do the anolog circuit wich implemented the phisycal
interface,there is some chip like SCMC U can use
As the last person pointed out an FPGA is only able to host the digital USB engine so an analog component is yet required .I have arrived to the conclusion that is cheaper not to integrate the USB interface on a FPGA ,,but to use a cheap self contained exteranl USB peripheral like the one from FTDI or cygnal devices .I easier and less expensive and much faster to design ...
As the last person pointed out an FPGA is only able to host the digital USB engine so an analog component is yet required .I have arrived to the conclusion that is cheaper not to integrate the USB interface on a FPGA ,,but to use a cheap self contained exteranl USB peripheral like the one from FTDI or cygnal devices .I easier and less expensive and much faster to design ...
I know what you mean when we compare intergration USB chip on FPGA and using extenal USB device, but as my opinion, I need to design a SOC so I think we should consider some problem about interface peripheral.