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Answered

Connecting diagnostics bus

LP.C 2 years ago in IQANdesign updated by Gustav Widén (System support) 1 month ago 7

Hi, I use an MD3 with 2 500kbps CAN and a 29 bits extended 250 kbps.  I can't connect the diagnostics bus to any of those buses.  Is there a way to bypass this error? I can't upload a new code with a recent version of IQANdesign.  Is there a way to bypass that?  What are my options here?


Thank you


LPC

Under review

The IQAN diagnostics bus is always 250 kbit/s, so combining it with any of the 500 kbps buses will not work.


In IQANdesign it is possible to combine the IQAN diagnostics bus with J1939, but I am guessing that if you are using Generic 29 bit and GFOUT/GFIN, it is not a J1939 bus that would easily be changed to JFOUT/JFIN ? 

That's right, it is not a J1939 bus, I have other generic CAN component on it.


LPC

That makes it quite tricky to upgrade to version 4 where a Diagnostics bus is necessary.

The workaround I can think of is to replace the GFIN and GFOUT channels with JFIN and JFOUT channels that give the same identifiers, and connect the GPIN and GPOUT channels to these instead. With the properties for J1939 Prio, PGN and SA it will be possible to set all bits except for the J1939 EDP bit, that is always zero.  

As an additional comment: 

In a single master system with only PC tools, modems and G11 on the Diagnostics bus, the IQAN diagnostics traffic is using  11-bit identifiers and will not collide with J1939 traffic. 

In IQAN multi-master systems, the diagnostics traffic between the masters is based on J1939 PDU1 messages, so there it would be possible to have a conflict with other 29-bit CAN

Are there any plans to change this back? I don't understand the shift to requiring a diagnostic bus? Previously, I never attached the diagnostic bus and never had a problem. 

+1

No plans to change this back. But, there are plans to allow Generic buses to share CAN port with other bus types . No date planned yet though.

Answered

I got reminded of this post while looking at the discussion on mixing the Generic bus with other types

https://forum.iqan.se/communities/1/topics/1110-j1939-generic-on-the-same-bus#

(currently no plan on doing this)

I realize the question raised on why  Diagnostics bus is required was never answered in this post. 

The motive was to promote the use of CAN as diagnostics on new machines as much as possible, wise from the experience of USB related troubles. A way of future-proofing the machine designs. 

Now we are gradually moving over to the MD3-M18 without USB, and also the MC2-M19 without USB