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CANBUS

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CANBUS

Postby B_Bercovitz » Sun Apr 09, 2017 1:46 am

I am trying to decide which picoscope would offer the most utility for my budget (~1500 usd). As the subject indicates I am presently interested in examining and decoding CANBUS signals. Are there a minimum specification that supports this ? Also what other specifications would allow for growth as a general scope capability ?

Thank you
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Re: CANBUS

Postby bennog » Sun Apr 09, 2017 5:00 pm

do you want to detect events that happen sometimes on a busy(200+ msg / sec) CAN bus.
Or do you just have some messages on a quiet (< 100 msg / sec) bus that you are interested in ?

How many busses do you want to examine at the same time ?
What is the speed(bps) of the bus ?

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Re: CANBUS

Postby B_Bercovitz » Mon Apr 10, 2017 8:16 pm

It is not a very busy BUS it is configured at 1 mb/s and has no more than 10-20 devices. I only want to examine one BUS at a time.

Brian
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Re: CANBUS

Postby bennog » Tue Apr 11, 2017 7:13 am

With a simple 2000 you can capture the CAN bus for short periods of time (2 - 10 messages)
If you take one with at least 32MS buffer memory you can use streaming mode (check streaming sampling rate > 9MS / s)
You can sample for about 5 or 10 seconds and decode all the messages in this window.

I use a 4444 scope for CAN examination, because of the floating inputs, with a normal (common ground scope) if you want to see what is happening you need 2 channels and subtract them from each other.
Below you see an image from a decoded message on a heavy loaded CAN bus (zoomed in from a 10sec capture)
In the left top corner you see a overview of the 10 sec capture.
You can also see why I use 2 channels and subtract the CAN-H and CAN-L The noise on the individual lines is from all the inverters in the machine. The differential signal is clean as you can see.

11-4-2017 09-03-46.png


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