fyi, the timing in 1-wire is in us not ns, ie RST is 480 us.
I have a simple arduino/Atmega program that can read timing on the 1-wire bus
if that would help. No scope needed!
-tmk
----- Original Message -----
From: "Pascal Baerten" <[email protected]>
To: "OWFS (One-wire file system) discussion and help"
<[email protected]>
Sent: Sunday, February 14, 2010 2:24:19 AM GMT -08:00 US/Canada Pacific
Subject: Re: [Owfs-developers] Help using an oscilloscope to monitor/diagnose
1-wire with OWFS
Hi Scott,
Measuring 1-wire traffic is done connecting your oscilloscope ground to GND and
measuring DQ. no special probe needed. Normally, quality oscilloscopes provide
enough ground isolation, and Tektronix certainly is.
I use the LA (logic analyser) function of my oscilloscope to verify protocol
sequences. Oscilloscope mode is usefull to measure level, transition dynamics,
attenuations etc...
Reading your post seems indicate that you try to catch logic signals sequences.
a reset duration is typically 480ns + 480ns =960ns
the rom command is 64 x 60ns = 3600 or even worse for search algorithm (x3)
then the function commands begins...
I quickly checked your osc capabilities, the most critical here is the buffer
deep fo samples: 2500 samples.
You have to setup a trigger on faillong edge as idle is 5v on DQ.
I ususally use a 1 ns sample interval when analysing 1-wire communication. With
this setting you'll able to capture 2500us data which is just too short.
reducing to 4 or 5ns sample intervall could increase you capture duration to
exploitable results.
As you have 2 channels, you could find usefull to differentiate master to slave
from slave to master:
playing with as comparator around a 100ohm resistor will give you this extra
info.
Also, OWFS may generate unexpected lot communication. Measure with only one
slave, use uncached, and avoid owhttpd.
hope this help.
Pascal
2010/2/13 Scott Jilek < [email protected] >
Let me preface by saying I am not an EE, but a Computer man who dabbles
in VERY basic electronics
I recently purchased an oscilloscope (Tektronix TDS-210) with the hopes
of expanding my electronics knowledge & abilities. I am trying to
monitor the data on my 1-wire net to diagnose some sensor issues. Some
documentation I found on Maxim's website [
http://www.maxim-ic.com/app-notes/index.mvp/id/244 ] suggests to either
1) use a differential probe or 2) do not ground the o-scope power cord.
Since I only have regular probes I picked up off eBay, I went for option
2 to pull the scope ground.
I've played around a bit, but am unable to reproduce the scope snapshots
any of the documentation shows. My 1-wire network works fine, I am able
to show devices & read a DS18S20 I'm trying to probe using OWFS, but I
am unable to see the logic transmission on the data as OWFS makes the
calls using the uncached directory. I've searched around for any info
on 1-wire and o-scopes but nothing gave me a breakthrough.
I know it's a bit off-topic, but can anyone suggest how to use a scope
to watch the protocol?
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--
Pascal
------------------------------------------------------------------------------
SOLARIS 10 is the OS for Data Centers - provides features such as DTrace,
Predictive Self Healing and Award Winning ZFS. Get Solaris 10 NOW
http://p.sf.net/sfu/solaris-dev2dev
_______________________________________________ Owfs-developers mailing list
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------------------------------------------------------------------------------
SOLARIS 10 is the OS for Data Centers - provides features such as DTrace,
Predictive Self Healing and Award Winning ZFS. Get Solaris 10 NOW
http://p.sf.net/sfu/solaris-dev2dev
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