I was looking into interfacing a NES with USB (2.0) flash memory. The memory is cheap (got a 64 meg stick free after rebate) and easily interfaces with any computer with a usb port and Windows 2000 or higher. This will provide plenty of space for roms and for realtime dumping memory. (Dual port RAM)

Currently I envision booting the nes up with an e(e)prom. (dev cart first for testing purposes) It will read whatever code is enough to tell it to retrieve the current Dev Firmware from the connected USB 2.0 memory stick. It will then load a Menu with the current loadable roms etc. Also it will be possible to load new and different FPGA information to handle mappers. But I'm getting ahead of myself.

The first thing to do is design the usb interface with the NES. The CY7C68000 TX2™ USB 2.0 UTMI Transceiver looks like a good start, but if there is another inbetween chip that could handle all the filesystem calls that would simplify everything.

Comments, suggestions, rude comments? :>

if you wanted to do simple file handling you could just section the usb into 512kb sections (is there any proper games above this?) this would give you plenty of slots to fit games in, you waste some space - but does that really matter?

Kirby's Adventure is 768 KBytes (512 KB PRG + 256 KB CHR), twice as big as Super Mario Bros. 3.

I did a little more research and took apart a USB flash disk. It has an oti2168, which basically makes flash act like a standard disk. So really all I need to learn are the basic commands to talk to a USB device directly. I probably should go and hack apart a motherboard with USB now. :>

Just a note in passing: these are common called "pen drives".

You can get a USB2.0 256MB pen drive for about US$40. They act *exactly* like a hard disk, using the standard USB mass storage model (which is part-of the USB1.x and 2.x specification -- it's not anything custom or proprietary). You can also boot directly from these devices, which should give people some interesting ideas (i.e. a bootstrap loader for images, etc.).

-- jdc

You might want to consider picking up a copy of "USB Complete: Everything You Need to Develop Custom USB Peripherals" by Jan Alexson. It's a fantastic piece of work, and should provide you with references to build what you need.

If you need a "more simple" reference, consider "USB Design by Example: A Practical Guide to Building I/O Devices" by John Hyde (of Intel). I own this book -- sadly, I can't recommend it for actually getting down to the nitty-gritty, but it goes over how USB works.

Generally speaking, Alexson's book is much MUCH more thorough, and is worth the money (US$33 vs. US$30 (used) for Hyde's book).

usb.org should contain a bunch of free reference tools (likely for the Windows platform, which shouldn't make much of a difference -- development is development!) and white papers for protocol specifications.

Oh, and one final thing: **PLEASE**, whatever you do, avoid using alternative indexes. They're annoying. :P

-- jdc

Oh, one thing I forgot: throughput.

On my SanDisk 256MB pen drive, I was able to get about ~400-500KBytes/second (write speed) via a USB2.0 interface. It's no blazing 480mbps, but it's flash memory, what do you expect. :-)

Anyways, that speed should suffice in general.

-- jdc

Well looking at it again I am thinking of using a CP2101 USB to UART bridge and then interfacing that with another UART to the NES. Then I only need to look up how to use the standard USB mass storage mode.

Oh and I took apart the Micro Advantage pen drive I got for free. It has an OTI2168, which basically does what the other pen you talked about does, makes flash act like a regular drive.

Anywho, what would be the best UART to use on the NES?

usb workings specs should be floating somewhere on web