[rescue] USB port card for sBus?

Jochen Kunz jkunz at unixag-kl.fh-kl.de
Sat Aug 23 03:19:17 CDT 2008

On Fri, 22 Aug 2008 21:35:10 +0200
"Arno Kletzander" <Arno_1983 at gmx.de> wrote:

> has anybody heard of a possibility to integrate USB support into
> computers with sBus yet, be it commercially available or as a
> homebrew project?
You will have to do it yourself.

There are three routes from my POV:

Build a SBus-USB host adapter from scratch in a FPGA. Doable, but may be not
trivial as USB is rather complex.

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.

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.

I don't know the ATARI USB interface. But given the complexity of USB
they must have taken the microcontroler route. I can not imagin that a 8-bit
ATARI can implement a full USB host port still leaving room for other things
like application software that uses the USB devices.

The microcontroler route is the way I would do it. The microcontroler provides
a working USB host port. So you don't need to fight that overcomplicated low
level USB protocol stuff. You would need only a bit of firmware on the
microcontroler to "mirror" the USB host port registers to the SBus and maybe a
DMA engine.

Then you need a USB host driver for the operating system of your choice...


Homepage: http://www.unixag-kl.fh-kl.de/~jkunz/

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