PicoScope 7 Automotive
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Yellow Can bus Scania?
Yellow Can bus Scania?
Hi all!
I want your input on this capture. It's my first try with Picoscope, just ran with standard Can-bus settings from the menu.
My concern is the distortion of the signal. Is it enough to disturb transmission of data?
I will try to get a recording when I have oppurtunity
I want your input on this capture. It's my first try with Picoscope, just ran with standard Can-bus settings from the menu.
My concern is the distortion of the signal. Is it enough to disturb transmission of data?
I will try to get a recording when I have oppurtunity
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Re: Yellow Can bus Scania?
Looks perfect to me.
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ben.martins
- Pico Staff Member
- Posts: 543
- Joined: Tue May 16, 2017 1:02 pm
Re: Yellow Can bus Scania?
Hello lastvagn8,
Thank you for your post and although not seeing the PSDATA file, I believe what you are seeing here is nothing to be concerned with.
The voltage “ringing” and “over-shoot” below is typical of automotive CAN signals and can be attributed to a number of factors such as the style of test lead (standard or high impedance) environmental noise, and “end of message” confirmation. Providing the effects are felt in both CAN H and CAN L then the differential nature of CAN will remove these effects. This can be seen perfectly when we apply a A-B math channel when CAN H is on channel A and CAN L is on channel B. Please see the following topic topic20981.html?&p=93851&hilit=fault+tolerant#p93851 for further information.
The ringing shouldn't have any effect on the data but I have noticed that your base idle voltages are not sitting where we would normally expect. Does the vehicle have faults present or are you just looking at known good signals to get used using the scope?
There is a lot of information on the forum regarding CAN and sometimes it can be difficult to pick out the topics amongst all the others. Here is a link to our useful information page where we have tried to collate all the relevant posts we have seen. topic15231.html#p57531.
I hope this helps and if you need any further assistance please don't hesitate to get in touch.
Kind regards
Ben
Thank you for your post and although not seeing the PSDATA file, I believe what you are seeing here is nothing to be concerned with.
The voltage “ringing” and “over-shoot” below is typical of automotive CAN signals and can be attributed to a number of factors such as the style of test lead (standard or high impedance) environmental noise, and “end of message” confirmation. Providing the effects are felt in both CAN H and CAN L then the differential nature of CAN will remove these effects. This can be seen perfectly when we apply a A-B math channel when CAN H is on channel A and CAN L is on channel B. Please see the following topic topic20981.html?&p=93851&hilit=fault+tolerant#p93851 for further information.
The ringing shouldn't have any effect on the data but I have noticed that your base idle voltages are not sitting where we would normally expect. Does the vehicle have faults present or are you just looking at known good signals to get used using the scope?
There is a lot of information on the forum regarding CAN and sometimes it can be difficult to pick out the topics amongst all the others. Here is a link to our useful information page where we have tried to collate all the relevant posts we have seen. topic15231.html#p57531.
I hope this helps and if you need any further assistance please don't hesitate to get in touch.
Kind regards
Ben
Re: Yellow Can bus Scania?
Thank you very much for a good and informative answer. This lorry has a fleetmanagement system installed, and there is a problem reporting values from the vehicle, like PTO-time, idling etc.
I was hoping to have found disturbance in the can-bus explaining the lack of information.
I tried to decode the can-messages but they all was corrupt, later I read some more and I might have the wrong bus-speed, I think it was 500 Kb/s, but i dont know the speed on the lorry, since I didnt measure the "one-bit packet"
This was the first test with my new Pico, after this test I've read some more. And the more I learn the more impressed i become.
regards
Jim from Sweden
I was hoping to have found disturbance in the can-bus explaining the lack of information.
I tried to decode the can-messages but they all was corrupt, later I read some more and I might have the wrong bus-speed, I think it was 500 Kb/s, but i dont know the speed on the lorry, since I didnt measure the "one-bit packet"
This was the first test with my new Pico, after this test I've read some more. And the more I learn the more impressed i become.
regards
Jim from Sweden
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ben.martins
- Pico Staff Member
- Posts: 543
- Joined: Tue May 16, 2017 1:02 pm
Re: Yellow Can bus Scania?
Hello Jim,
I think the reason for not getting any decoded packets is down to the amount of time you have on the screen. Using the preset is great to ensure the structure of the packet is ok but you would need more time to actually decode the date.
If you were to set up your scope to have CAN H on channel A, CAN L on channel B and 10ms/div of time with at least 1MS. I've added a settings file to my google drive which you should be able to download from here https://drive.google.com/open?id=1sdOn4 ... Fw3jSORkd2. This will gather much more data and providing the packets are good, then we should see it decode. Am currently looking for J1939 data with faults that are present, so if you do manage to catch some please feel free to send on to me.
If you could help that would be great.
Kind regards
Ben
I think the reason for not getting any decoded packets is down to the amount of time you have on the screen. Using the preset is great to ensure the structure of the packet is ok but you would need more time to actually decode the date.
If you were to set up your scope to have CAN H on channel A, CAN L on channel B and 10ms/div of time with at least 1MS. I've added a settings file to my google drive which you should be able to download from here https://drive.google.com/open?id=1sdOn4 ... Fw3jSORkd2. This will gather much more data and providing the packets are good, then we should see it decode. Am currently looking for J1939 data with faults that are present, so if you do manage to catch some please feel free to send on to me.
If you could help that would be great.
Kind regards
Ben