On 03/19/2008 @ 17:37, Womo wrote :

:
: woahah, hey, Nate,
:
: you already gave us some hints then and there, but this sounds very promising. Well, Spiro always wanted to add an 8K RAM with SPI interface. Although I found such a chip recently, it is not generally available. With only adding such a chip to the programming interface (MOSI, MISO and SCK), extending the existing xu1541 would be super easy.

I don't like SPI since it's slow and an external, expensive part.

: I, on the other hand, prefer the "integrated way", selecting a microcontroller that is fast enough to do the parallel burst protocol without buffering.

Yes, that is my approach.

: The relatively new Atmel AT90USBxxxx chips would be fast enough and more or less compatible to existing firmware source. With Atmel's USBKey there is a cheap development board available...

Yes, I'm using an AT90USBxxx and the MyUSB library. It provides a nice wrapper around the built-in "DMA" for USB transfers. We only need to hit 40 KB/s (5000 xfers/s) to match a 300 RPM drive. Should be no problem.

The only question is how small we can break the transfers down so the cheapest part will work. I will get it operational with the highest performance part and then see how to cost reduce.

: There are more solutions thinkable and I'm curious what your's is looking like. Don't you want to post some pictures?