J1939 Timeouts what really happens on an IQAN master when one is sensed

Andy 4 months ago in IQANdesign updated 4 months ago 0


Hey People

Im interested in what occurs on a IQAN master when a Timeout that is attached to a J1939 JFIN occurs. I cant find anything int he manual that comes with Design and suspect that teh standards might well cover it, but I dont have them.

Why the question?

I have a 3rd party J1939 module on an MD4-10 Canbus C bus that is shared with a wired CanOpen remote and a wireless CanOpen remote. Due to e recent change requested of me I was seeing disconnects occurring with the module that controls the engine RPM via a 0-5V output. When the module disconnected it never reconnects, until I shut down the IQAN master and restart it. The disconnect next time occurs at roughly the same sequence of events that caused the first so its repeatable. prior to the last change I made in the throttle control we had seen very occasional disconnects, but with the change it occured every time we tried to advance from high idle to work rpm

I changed the 2 JFOUT channels from "Continuously" (100mS interval) to "On change" and changed the JFIN timeout from not set to 300mS (The device was set to continuously every 100mS). This meant that when the disconnects occurred and they still did at the same point in sequence but within a short time after the comms were reestablished. The small timeframe of disconnect meant that the end rpm on the engine may not have ended up being exactly what it should have been but any subsequent press of a throttle control that resulted in a changed frame value meant that we got what we needed. I suspect that the issue was actually solved by the timeout on the JFIN and not the change to the JFOUT frames. I didn't have sufficient time on the machine to test this, but will make a new load including this change for the next mechanics on site.


1) what exactly does a timeout  occurring trigger within the master, why does it reconnect when it didnt without the timeout set

2) How can i fault find the disconnect and understand why its occurring. The other bus members are not disconnecting and we are seeing no remote lag that might be a disconnect reconnect process occurring. I presume that our USB canbus dongle wont help because what ever is occurring is probably outside of the j1939 protocol and further down the stack closer to the physical interface? Logic Analyser??? Which is probably as big a project in itself as the whole rest of the design project

Would appreciate any guidance from you who have been here before

Ive attached a subset of my project (First line of the post) that relates to the J1939 module I'm talking about. The settings are as they were when the issue causing the disconnect occurred.