Why does CAN J1939 decoding require connected scope ?

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nurber
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Why does CAN J1939 decoding require connected scope ?

Post by nurber »

Hi Forum. If my scope (4444) is attached when I open a particular .psdata with decoded J1939 then I see decoded data and see "CAN J1939" among the list of available decoders. If I open the .psdata in demo mode without 4444 attached then I don't see J1939. Is there some processing of J1939 data that only happens on scope ?

Sven

nurber
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Re: Why does CAN J1939 decoding require connected scope ?

Post by nurber »

I should be able to decode J1939 without scope attached ?

Willem43
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Re: Why does CAN J1939 decoding require connected scope ?

Post by Willem43 »

nurber wrote:
Sun Jun 02, 2024 2:02 pm
Is there some processing of J1939 data that only happens on scope ?
Sven
Just thought I will let you know that I do not get a CAN J1939 in my list of serial decoders either, with or without my 2207B MSO attached.
Using the latest version of PicoScope 7 T&M – Early Access.
I have not seen any decoder, at least the not ones I use, require the scope to be connected. I can decode my saved .psdata files at any time.

I have seen somewhere that the CAN J1939 decoder is included in PicoScope for models 4000, 5000 and 6000 Series oscilloscopes. So maybe it needs the scope to determine if the decoder should be available. It also seems that the scope model saving a .psdata file is not recorded in the file - at least that is my impression.

nurber
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Re: Why does CAN J1939 decoding require connected scope ?

Post by nurber »

Thanks for replying Willem43. Yes, I do remember seeing that J1939 only works for certain series of scopes. I'd thought this was due to capability of scopes (i.e. buffer memory ), but as I remember some larger buffer versions of 3000 series perhaps this isn't the case. All processing of data is happening in host PC so it really shouldn't make a difference about scope used if you have captured waveform(s) to disk. So is this because Pico doesn't want people who spent less $ to get certain features like J1939 ?

Willem43
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Re: Why does CAN J1939 decoding require connected scope ?

Post by Willem43 »

nurber wrote:
Sun Jun 09, 2024 11:03 pm
So is this because Pico doesn't want people who spent less $ to get certain features like J1939 ?
I would think/hope that is not the reason. I suppose we will have to wait for a responds from Pico.

nurber
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Re: Why does CAN J1939 decoding require connected scope ?

Post by nurber »

I had an informative email exchange with Picoscope and learned the following:

-Only T&M 4000 series scopes get J1939 decoder because the programming of it is specific to same 4000 series from Automotive.
-You can run Automotive software in demo mode (without a connected scope) to decode J1939 from .psdata. As a result I've created a virtual machine on Linux as Ubuntu doesn't allow for both T&M and Automotive to be installed at the same time. This way I can use .psdata files with J1939 without having to connect my scope.
-As to why T&M prevents decoding of J1939 in .psdata while Automotive does not, it's about limiting access. I don't understand this although I didn't pursue further. How many people with scopes other than 4000 series are going to need to display J1939 data in .psdata files particularly if their scopes can't capture the J1939 in the first place ?

nurber
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Re: Why does CAN J1939 decoding require connected scope ?

Post by nurber »

although perhaps I'm missing an important point which is that .psdata by it's nature is just about raw data and the display of CAN/J1939 or any other protocol is about processing on the host ?

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