Why is a there a constant high bus load?

CAN FD Interface for High-Speed USB 2.0
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Daniel Fowler
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Joined: Fri 1. Jun 2018, 12:45

Why is a there a constant high bus load?

Post by Daniel Fowler » Fri 1. Jun 2018, 13:16

Hello,

I need to get the PCAN-USB FD devices I'm using to work reliably.

At the moment I send a single message in PCAN-View and the bus load immediately jumps high and stays there, even though nothing is being transmitted. The LED is flashing red and status in PCAN-View shows Error Passive Warning. This happens nearly every time a message is sent, even if nothing is connected to the PCAN-USB FD device.

Why does the bus load stay high when there is no data flowing on the CAN port?

Thanks.
DAN

G.Lang
Support
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Posts: 139
Joined: Wed 22. Sep 2010, 14:58

Re: Why is a there a constant high bus load?

Post by G.Lang » Fri 1. Jun 2018, 14:36

Hi Daniel,

thanks for your request. It looks you are a CAN newbie :-)
Please take a look at the following topic in our forum to understand what´s "wrong", especially the question from "Lukast85" and the answer from K.Wagner

https://www.peak-system.com/forum/viewt ... ight#p5230

For more infos about "Error passive" (also known als Busheavy) please take a look at the following topic in our forum:
https://www.peak-system.com/forum/viewt ... f=120&t=39

best regards
Gunther

Daniel Fowler
Posts: 3
Joined: Fri 1. Jun 2018, 12:45

Re: Why is a there a constant high bus load?

Post by Daniel Fowler » Fri 1. Jun 2018, 15:18

The posts you pointed me to do not help me understand the issue.

What is the bus load chart displaying if there is no CAN data being sent or received by the PCAN-USB device?

Why is PCAN-View displaying "Error Passive" when only a single CAN message, with no data bytes (DLC=0), is sent?

Why does a single message cause the error count to jump to 127 immediately and trigger the Error passive state?

I'm trying to understand why the PCAN-USB device immediately enters an error condition.
Thanks.
DAN

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U.Wilhelm
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Joined: Fri 10. Sep 2010, 19:34

Re: Why is a there a constant high bus load?

Post by U.Wilhelm » Fri 1. Jun 2018, 15:49

Please see CAN Basic Tutorial - This have nothing to do with our Devices - thats how CAN work!
If you send out a single CAN Frame to a CAN Network where NO OTHER CAN Device is working (same Bitrate, active mode), the CAN Controller will never get a ACK (because there is no CAN node that could ACK) and so the CAN Core send the CAN Frame again and again and again..
Result:
* Bus Errors
* 100% Busload

This is the same info that my colleauges Keneth write in the Post where Gunter send you to...
--------------------------------
PEAK-System Technik
Technical Support Team
support@peak-system.com
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Daniel Fowler
Posts: 3
Joined: Fri 1. Jun 2018, 12:45

Re: Why is a there a constant high bus load?

Post by Daniel Fowler » Sun 3. Jun 2018, 19:30

Thanks, that makes sense.
DAN

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