Author Topic: oscilloscope suitable for analyzing 10BASE-T signal  (Read 8363 times)

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Offline m4rtin

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oscilloscope suitable for analyzing 10BASE-T signal
« on: October 02, 2013, 08:22:10 am »
I would like to analyze 10BASE-T Ethernet signal with oscilloscope. Signaling rate for 10BASE-T is nominally 10 MHz. An all-1's Manchester-encoded signal will result in a 10 MHz waveform. However, as this document by Fluke Networks states, the 10 MHz is a bare minimum. I would prefer if I could connect the oscilloscope with my PC(or at least later upload the measurements to PC). Any suggestions to specific model/lineup or experience with analyzing 10BASE-T Ethernet signal?
« Last Edit: October 02, 2013, 08:34:21 am by m4rtin »
 

Offline Rerouter

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #1 on: October 02, 2013, 08:31:57 am »
what about it do you wish to measure? eye diagrams? real time triggering and decoding? etc
 

Offline m4rtin

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #2 on: October 02, 2013, 09:00:18 am »
what about it do you wish to measure? eye diagrams? real time triggering and decoding? etc

I would like to analyze an Ethernet frame in way that I can see the raw AC signal(constantly varying signal voltages on y-axe) on the wire in real time, save the results and later analyze the results. By analyzing I mean to analyze the encoding, find the MAC address bit-pattern in the saved oscilloscope data etc.
 

Offline TMM

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #3 on: October 02, 2013, 09:05:23 am »
If you aren't interested in the signal integrity, but rather just the data, use a logic analyser.
 

Offline nctnico

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #4 on: October 02, 2013, 01:44:30 pm »
Better yet use a PC with Wireshark to capture and analyse ethernet data. A scope or a logic analyser are utterly useless for analysing network data. You may need to use a hub instead of a switch in order to capture all the data to/from a host. Ethernet hubs (10Mbit or 100Mbit) can be bought thru Ebay.
There are small lies, big lies and then there is what is on the screen of your oscilloscope.
 

Offline m4rtin

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #5 on: October 02, 2013, 04:46:18 pm »
If you aren't interested in the signal integrity, but rather just the data, use a logic analyser.

For testing the signal integrity I should use oscilloscope with eye diagram support?

Essentially I need a device which is capable of  displaying and storing a waveform like this:



As I don't have an oscilloscope nor a logic analyzer, I thought I buy one which can be used later for some other measurements if needed.


Better yet use a PC with Wireshark to capture and analyse ethernet data. A scope or a logic analyser are utterly useless for analysing network data. You may need to use a hub instead of a switch in order to capture all the data to/from a host. Ethernet hubs (10Mbit or 100Mbit) can be bought thru Ebay.

I'm aware of this, but I need to show an electrical signal of an Ethernet frame.
 

Offline m4rtin

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #6 on: October 04, 2013, 09:42:31 am »
If you aren't interested in the signal integrity, but rather just the data, use a logic analyser.

Ok. But any suggestions on specific PC-based logic analyzer below 300$? As I understand, in case of PC-based logic analyzers, the software capabilities and user interface is as important as the capabilities of the logic analyzer itself. Logic analyzer should support at least 20MHz and from +2.5V to -2.5V. Other than that, it should be as simple as possible as I have no previous experience with such tool :)
 

Offline dfmischler

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #7 on: October 04, 2013, 10:03:09 am »
My question is: why would anyone care?  10baseT is no longer in widespread use (just in legacy devices).  And you need better equipment for 100baseTX or 1000baseT.
 

Offline BillyD

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #8 on: October 04, 2013, 10:09:55 am »
And you would have one hell of a job to try and decode it back into meaningful data, if it's even possible. Though not to say that it wouldn't be very educational and entertaining, which may be part of the objective here.
 

Offline m4rtin

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #9 on: October 04, 2013, 01:48:18 pm »
dfmischler, BillyD: I need this for educational purposes. I would like to analyze 10BASE-T because it has smaller frequency than 100BASE-TX or 1000BASE-T and thus one could use affordable oscilloscope or logic analyzer.

A Rigol DS2000 series, possibly with the memory upgrade, should be suitable. You can connect it to your PC for control and downloading captured waveforms.

Unfortunately this is way out of my budget. Salae logic analyzer seems to be perfect, but it accepts voltages from -.5V to 5.25V while 10BASE-T uses -2.5V to +2.5V.
 

Offline creyc

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #10 on: October 04, 2013, 01:57:29 pm »
A logic analyzer is not going to give you a waveform like the image you posted, with rising/falling edges, but a digitized square wave version of the signal data.  Do you need to see the actual waveform?
 

Offline m4rtin

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #11 on: October 04, 2013, 02:26:11 pm »
A logic analyzer is not going to give you a waveform like the image you posted, with rising/falling edges, but a digitized square wave version of the signal data.  Do you need to see the actual waveform?

Does logic analyzer decode the actual waveform? Or does it just convert the waveform to digitized square waves?
 

Offline Bored@Work

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #12 on: October 04, 2013, 02:48:52 pm »
A logic analyzer is not going to give you a waveform like the image you posted, with rising/falling edges, but a digitized square wave version of the signal data.  Do you need to see the actual waveform?

Does logic analyzer decode the actual waveform? Or does it just convert the waveform to digitized square waves?

Cheap logic analyses won't help you at all. They will try to interpret the signal on the cable as simple logic ones and zeros. Which they aren't. 10 BASE-T uses a differential signal. You would have to convert that to single-ended for a cheap analyser. Further, 10 BASE-T uses a number of specific waveforms to performs some operations, like link tests and signaling idle. What a cheap analyses makes of these? No idea. The actual data is using Manchester code for the line encoding, where they have taken the high-frequency edges off.

The tools commonly available to decode such a signal are called NICs -  network interface controllers. Your PC already includes one or more. You probably know it as the network plug on your PC. Plug the cable in, run a software like Wireshark and get more signal decoding and interpretation than you can shake a stick at.
« Last Edit: October 04, 2013, 02:50:42 pm by Bored@Work »
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Offline m4rtin

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Re: oscilloscope suitable for analyzing 10BASE-T signal
« Reply #13 on: October 08, 2013, 11:29:21 pm »
Cheap logic analyses won't help you at all. They will try to interpret the signal on the cable as simple logic ones and zeros. Which they aren't. 10 BASE-T uses a differential signal. You would have to convert that to single-ended for a cheap analyser. Further, 10 BASE-T uses a number of specific waveforms to performs some operations, like link tests and signaling idle. What a cheap analyses makes of these? No idea. The actual data is using Manchester code for the line encoding, where they have taken the high-frequency edges off.

This means that I need to go with oscilloscope and logic analyzer can be set aside? So can anyone suggest a (PC based) oscilloscope with memory which is able to measure signals with frequency up to 20MHz and from +2.5V to -2.5V?


The tools commonly available to decode such a signal are called NICs -  network interface controllers. Your PC already includes one or more. You probably know it as the network plug on your PC. Plug the cable in, run a software like Wireshark and get more signal decoding and interpretation than you can shake a stick at.

As I explained before, I need the electrical signal of the frame for educational purposes. I know how to use Wireshark, tcpdump or tshark :)
 


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