Subject:
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Re: [Legousb-devel] Yes, the puzzle is solved - legousbtower + nqc for linux.
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Newsgroups:
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lugnet.robotics
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Date:
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Tue, 15 Jan 2002 00:27:25 GMT
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Original-From:
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Stuart Northfield <stu@janitorium%antispam%.co.uk>
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Viewed:
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1324 times
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At 23:00 -0500 2002-01-11, PC CHAN wrote:
> Dear Juergen and Andy,
>
> I found the option to turn on data debugging on legousbtower this
> evening. It all turned out to be an issue between uhci and legousbtower.
>
> From the out_callback I could tell, it always sent 8 bytes no matter
> what tower_send submitted. The RCX brick was probably choked by the
> extra bytes.
>
> Looking at the uhci code, I found that it was dma'ing acording to
> urb->transfer_buffer_length instead of the urb->actual_length.
>
> I don't have the specifications to tell what uhci should be looking at.
> Anyway I modified tower_send to submitted bytes_to_write as
> buffer_length as a workaround/fix.
I believe this is correct. actual_length is only used on incoming
data because the amount of data supplied may be less than the maximum
buffer size (held in transfer_buffer_length).
On the transmission side you just use transfer_buffer_length
> It is now working!!!
Excellent...now to see if it is any better on the OHCI HCD.
Stu
--
The Janitorium <http://www.janitorium.co.uk/>
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