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List:       libusb-devel
Subject:    Re: [libusb] USB Packets lost on "newer" CPUs...
From:       Hans Petter Selasky <hps () selasky ! org>
Date:       2014-05-23 9:45:54
Message-ID: 537F18D2.6070404 () selasky ! org
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On 05/21/14 17:51, Erik Rull wrote:
> Hi all,
>
> I'm running an embedded environment and use libusb for talking with an FTDI USB
> 2 chip (raw) with PID/VID 0403:6001. This worked great on Pentium-M, ATOM N160
> and Core2Duo Txxxx series. Now I switched the CPU to an i3 QM77 chipset and the
> communication starts losing packets. The chance of a packet loss is > 10%, when
> asking for small packets they are transmitted fine in most attempts, but larger
> communication streams are nearly never completed. Some dozens of bytes are
> finally missing. I use only synchronous bulk transfer, I checked also the timing
> and added several delays, reduced the amount of data read in one block - no
> success.
>
> Software is exactly the same on all systems, USB 3.0 is disabled.
>
> I tried libusb 1.0.18 and 1.0.17 both with the same behavior.
>
> Any ideas how to proceed to find the source of evil? There are NO errors
> reported by libusb, neither by dmesg. I just have not enough or no data at the
> end.
>
> The USB transfer itself is great, when using a USB key and transfer data from /
> to it everything succeeds without any error.
>
> Thanks.
>
> Best regards,
>
> Erik

Hi,

If data is lost, it might be a data toggle issue. You need a bus 
analyzer to catch these kind of issues.

--HPS


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