[rescue] USB port card for sBus?

[Joshua Boyd]

On Aug 23, 2008, at 4:19 AM, Jochen Kunz wrote:
>
> Build a SBus-USB host adapter from scratch in a FPGA. Doable, but  
> may be not
> trivial as USB is rather complex.

Yeah, that sounds like a bad idea.

> Use a USB host adapter chip as found in other computers. This chips
> have a PCI (maybe PCIe) host interface. So you have to build a SBus to
> PCI bus bridge. This is not trivial as you have to implement the PCI
> host bridge e.g in a FPGA.

Actually, there is a PCI->wishbone bridge already, so if I understand  
correctly, only a SBUS->wishbone bridge would need to be written.

> Use a microcontroler with USB host interface as a smart USB host
> adapter. In that case you have to glue the microcontroler somehow to
> the SBus. This is much simpler as a SBus-PCI bridge and should be
> doable as a homebrew project. This also has the advantage that you can
> offload USB protocoll work to the microcontroler. Most likely you  
> will end up
> with somthing like an Atmel AT91RM9200 ARM based microcontroler and  
> maybe a
> FPGA for the glue logic.

That would also be cool.
>
> Then you need a USB host driver for the operating system of your  
> choice...

Actually, if the OS of choice is NetBSD (or OpenBSD, or FreeBSD) and  
he used the SBUS->FPGA->PCI route, wouldn't he only need a SBUS->PCI  
driver for the FPGA?