Ethernet testing methods

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snap4749
Newbie
Posts: 5
Joined: Fri Jun 26, 2020 7:52 am

Ethernet testing methods

Post by snap4749 »

Hello gents , can anyone please or direct me on testing procedures for Ethernet network on vehicle with sos module , I have got an vehicle with comm issue followed by SOS warning lights and U code with Ethernet branch 4 malfunction and fault for communication issue , any thoughts really appreciated.

ben.martins
Pico Staff Member
Pico Staff Member
Posts: 534
Joined: Tue May 16, 2017 1:02 pm

Re: Ethernet testing methods

Post by ben.martins »

Hi snap4749,

Firstly I must apologise for the delay in getting back to you on this.

Ethernet testing isn't for the faint hearted as there are varying different speed levels in vehicles at the moment for Ethernet. You have 10BaseT and 100BaseT which sit at 10Mbs and 100Mbps respectively. BroadReach has a bandwidth of around 33kHz from memory so realistically with the 4425A, 10BaseT is the only one we could measure accurately but use of x10 attenuated probes is a must like we do with Flexray. Even then, decoding is not going to be possible with the way Ethernet scrambles the messages.

You could 'see' activity with the other networks but other than comparing relative to a known good, it's hard to determine anything else. Some of our users have demonstrated Ethernet captures such as people on our FaceBook group page like Kris Williams - https://www.facebook.com/Kriswilliamsdi ... bLFaEP9ful.

Ethernet is getting faster and faster and any sort of connection to a network like this will have an effect on the raw signal. With the bandwidth pushing higher and higher the cost of a scope to measure these signals will be pushing scope budgets! Connection is also a problem as Ethernet cables do not lend themselves to being back probed.

So, really this only leaves a couple of options. Standard cable testing using resistance, I would be cautious about load testing Ethernet cables! And finally cable substitution where bypassing the installed Ethernet cable with a known good cable.

If you have a PicoScope it will be interesting to see any captures you might get. It would be advisable to use the high impedance x10 probes when capturing and a high sample rate.

I hope this helps.

Kind regards

Ben

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