Folks,

I've got a project where my board effectively envelops an existing USB widget: my board would look, to a PC, like the enveloped USB device and, to the device, like a PC. It will pass through the majority of traffic untouched, but will monitor traffic and intercept/delay some of it so that it can work its wonders prior to passing on said packets.

I've done a lot of communications protocol work, but have yet to touch USB; generally, how big of a disaster might implementing this bridging functionality end up being? E.g., am I going to need a boatload of buffer memory in order to do packet store and forwarding, or can I negotiate things down on both ports to the 10s-100s of bytes range?

On the hardware side, any suggestions would be welcome. I've previously worked with the Cygnal/Silabs 100 Mhz part via the Keil toolchain, and very much enjoyed the debug support that's built into the chip, e.g. the ability to set multiple breakpoints. However, having been away from the 8051 world for quite awhile, I'm ignorant as to whether equivalent support has become commonplace among other vendors. Also, since I'm going to need to implement both a host and a device port, I imagine that I'm going to need something beyond just the microcontroller, as I'm guessing that they only implement device-side, and not host-side, USB functionality. I'm willing to go outside of the 8051 world, although that would entail purchase of another toolchain.

Also, what's the high cost of a USB protocol analyzer these days?

Thanks in advance,
David