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List: owfs-developers
Subject: Re: [Owfs-developers] possible bus search modification
From: Paul Alfille <paul.alfille () gmail ! com>
Date: 2015-06-13 15:12:52
Message-ID: CAP_SGzdEWWO0Pn0GDS3QCF=bOBCuO6qtAM5-3tBXFtm-ZZdHqA () mail ! gmail ! com
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Are you talking about the "presence pulse" when the device is connected?
OWFS doesn't monitor that directly (it's possible some hubs might have
internal detection).
On Thu, Jun 11, 2015 at 11:09 AM, Howell, Larry (Contractor) <
Larry.Howell@stryker.com> wrote:
> Hi list,
>
>
>
> Our project is developing an embedded system running Linux 2.6.35 on an
> i.MX53. The system utilizes data from DS2505s through DS2482-800 bus
> master. We're using owfs-2.8p15 and the initialization parameters are
> ‘i2c=/dev/i2c-2:0 –m mnt/1wire --allow_other'.
>
>
>
> Physically disconnecting the DS2505 from the system requires 0.5-2
> seconds. OWFS has generally performed well with the application code
> reading uncached data. However, system noise is causing bus search errors
> when the read Serial Number (SN) on a bus doesn't match the first time read
> and stored SN, which results in a logical disconnection of DS2505. The
> system noise doesn't seem to corrupt the presence pulse due to its pulse
> width.
>
>
>
> A suggested fix is to only do a bus presence check to maintain the DS2505
> is connected after the first read. If bus presence is not detected, then
> next time bus presence and reading of SN to be implemented to restart the
> process. Suggested fix is shown as a sequence below:
>
> First time -> Read bus presence and 64-bit SN -> Result success -> Read
> memory -> check integrity -> Result success
>
> Second time -> Read bus presence -> Result success
>
> | |
>
> Nth time -> Read bus presence -> Result failure
>
> N+1th time -> Read bus presence and 64-bit SN … (Repeat as if it is first
> time)
>
>
>
> I'm requesting suggestions about the best way to implement the suggested
> fix. Any pointers or suggestions on handling the noise problem would be
> greatly appreciated.
>
>
>
> Thanks,
>
>
>
> Larry Howell
>
>
> ------------------------------------------------------------------------------
>
> _______________________________________________
> Owfs-developers mailing list
> Owfs-developers@lists.sourceforge.net
> https://lists.sourceforge.net/lists/listinfo/owfs-developers
>
>
[Attachment #5 (text/html)]
<div dir="ltr">Are you talking about the "presence pulse" when the device \
is connected? OWFS doesn't monitor that directly (it's possible some hubs \
might have internal detection).<div><br></div><div><br></div></div><div \
class="gmail_extra"><br><div class="gmail_quote">On Thu, Jun 11, 2015 at 11:09 AM, \
Howell, Larry (Contractor) <span dir="ltr"><<a \
href="mailto:Larry.Howell@stryker.com" \
target="_blank">Larry.Howell@stryker.com</a>></span> wrote:<br><blockquote \
class="gmail_quote" style="margin:0 0 0 .8ex;border-left:1px #ccc \
solid;padding-left:1ex"><div lang="EN-US" link="blue" vlink="purple"><div><p \
class="MsoNormal">Hi list,<u></u><u></u></p><p class="MsoNormal"><u></u> \
<u></u></p><p class="MsoNormal">Our project is developing an embedded system running \
Linux 2.6.35 on an i.MX53. The system utilizes data from DS2505s through DS2482-800 \
bus master. We're using owfs-2.8p15 and the initialization parameters are \
‘i2c=/dev/i2c-2:0 –m mnt/1wire --allow_other'. <u></u><u></u></p><p \
class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">Physically disconnecting \
the DS2505 from the system requires 0.5-2 seconds. OWFS has generally performed \
well with the application code reading uncached data. However, system noise is \
causing bus search errors when the read Serial Number (SN) on a bus doesn't match \
the first time read and stored SN, which results in a logical disconnection of \
DS2505. The system noise doesn't seem to corrupt the presence pulse due to its \
pulse width.<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p \
class="MsoNormal">A suggested fix is to only do a bus presence check to maintain the \
DS2505 is connected after the first read. If bus presence is not detected, then \
next time bus presence and reading of SN to be implemented to restart the process. \
Suggested fix is shown as a sequence below:<u></u><u></u></p><p \
class="MsoNormal">First time -> Read bus presence and 64-bit SN -> Result \
success -> Read memory -> check integrity -> Result \
success<u></u><u></u></p><p class="MsoNormal">Second time -> Read bus presence \
-> Result success<u></u><u></u></p><p class="MsoNormal"> \
| \
|<u></u><u></u></p><p class="MsoNormal">Nth time -> Read bus presence -> \
Result failure<u></u><u></u></p><p class="MsoNormal">N+1th time -> Read bus \
presence and 64-bit SN … (Repeat as if it is first time)<u></u><u></u></p><p \
class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal">I'm requesting \
suggestions about the best way to implement the suggested fix. Any pointers or \
suggestions on handling the noise problem would be greatly \
appreciated.<u></u><u></u></p><p class="MsoNormal"><u></u> <u></u></p><p \
class="MsoNormal">Thanks,<span class="HOEnZb"><font \
color="#888888"><u></u><u></u></font></span></p><span class="HOEnZb"><font \
color="#888888"><p class="MsoNormal"><u></u> <u></u></p><p class="MsoNormal"><span \
style="color:#1f497d">Larry \
Howell<u></u><u></u></span></p></font></span></div></div><br>------------------------------------------------------------------------------<br>
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<br></blockquote></div><br></div>
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