Well you are using the Virtex-5 FPGA Family, but what Development Board are you using?
I don't know that anybody has developed a FPGA bitstream for Ethernet on the boards, but RS-232 is way too slow to be of any use. You can program it via RS-232, but it would have to be written to operate over the network.
Could you provide a picture of the dev board? Please provide multiple views so we can see all the GPIO.
And did you buy these up or did you happen to run across some spares?
I want to try to usb, but I think the result is not optimal
Why do you say not optimal? What do think will be the deficiency? Remember mining is not about IO bandwidth, at least on the mining rig side.
I think he has an older development board, and I'm assuming they've never done anything with FPGA's before.