If you would simply like to connect a microcontroller board to a computer using USB but don't need massive bandwidth (less than 800kb/s), then you may want to have a look at the smaller and cheaper USB8Bit board.

First of all, the software part is not as easy as with the USB8Bit board, especially if you're after high transfer rates. In order to write your own software, you need:

• The CY7C8601xA Data Sheet and, even more important, the EZ-USB Technical Reference Manual, both available from Cypress.
• An '8051 compiler like SDCC for the firmware.
• libusb, including headers, GCC, and of course all the usual development tools assumed to be on the hard drives of anybody who is surfing these pages...

Here is a list of local and external resources around the FX2:

• My software collection: Local tools and examples verified to work with my FX2 board, including high-speed IO transfer program FX2Pipe.
• USB Live Osci, my a little dual 8 bit 10MS/s sampling USB oscilloscope.
• SSRP: Simple Software Radio Peripheral; basically an AD converter connected to the FX2. Fast IO source code.
• FX2 programmer, another programmer similar to my one, and also check out the software radio link on that page.

As shown in the schematic above, you can attach an EEPROM (e.g. 24LC64) to the FX2 in order to permanently store the firmware for the 8051. This way, you do not have to download the firmware each time the FX2 is plugged into the USB. Instead, it starts up with the firmware and can configure the endpoint descriptors. Here is how you do it.