Joel Sherrill <> joel.sherrill at
Fri Sep 16 16:45:14 UTC 2005

Camilo Alejandro Arboleda wrote:
> Hello,
> I have a basic question, has any one in the list evaluated the effort 
> need to implement USB supppor in RTEMS?

There was an abandoned effort by OAR to port the NetBSD USB stack to 
RTEMS.  We had really bad luck and had a customer board which had
a broken PCI interface.  By the time we all realized the hardware
was broken and verified it, the delivery had slipped too much and
the project was canceled.

I can tell you from memory the USB stack in all *BSD is the same
code so that is a good thing.  I worked to identify a "BSD kernel kit"
which was the code shared between the TCP/IP stack and the USB stack.
The code itself had a porting section of primarily one header file.
It supported UHCI, EHCI, and OHCI and it was fairly straighforward to
make sure all compiled even if we didn't test them.  There is a set
of abstract device classes which had to be worked through.  For example,
the USB NICs had adapters to the TCP/IP stack.  USB mice had a protocol
they had to adapt to.

The last hurdle I remember needing to address was that the stack
depended the BSD kernel device tree and I was working to figure
out to initialize that to a satisfactory state in RTEMS.

AFAIK this is the farthest anyone has gotten.

Joel Sherrill, Ph.D.             Director of Research & Development
joel at                 On-Line Applications Research
Ask me about RTEMS: a free RTOS  Huntsville AL 35805
    Support Available             (256) 722-9985

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