: switchable or separate termination in can network

Bram,
Perhaps the information on Body Builder Plus (BBI +) site www.daf.com is useful for you?

http://www.dafbbi.com/

Met vriendelijke groet / With kind regards, 
Koen van Erp
Technical Trainer/Author
_________________________________
DAF Trucks N.V. - Service Training



http://www.dafbbi.com/
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Bram Kerkhof
Sent: Thursday, June 25, 2015 10:36 AM
To: [email protected]
Subject: RE: [CANLIST] switchable or separate termination in can network

My personal preference would be to hunt down the designer of the nodes with soft-switchable terminators for a very stern talking-to on why that is never a clever idea. (unless we are talking about FT-CAN, where switchable termination is part of the deal). Hard-switchable terminators
(jumpers/cables) should be measurable with a powered-down network, so that should not matter.

In practice, I don't see an easy way to detect soft-switchable termination unless you have the proper equipment (which ranges from not-so-cheap to
eye-wateringly-expensive) and skills. In the real world, telematics installers get a multimeter and a flowchart, and maybe a way to determine if the CAN network is working (diagnostics output of the node they are installing). So your best bet would be: follow the "regular" directions, see if the CAN network functions afterwards and if not: invert the termination setting of the device you installed to see if that fixes things. If that doesn't work, bring in the fancy equipment and engineers, start unplugging/unpowering nodes from the network, and spend the best part of the day trying to figure out what is happening.

cheers,
Bram
-----Original Message-----
From: [email protected] [mailto:[email protected]] On Behalf Of Hadarits Kft.
Sent: woensdag 24 juni 2015 21:58
To: [email protected]
Subject: [CANLIST] switchable or separate termination in can network

Hi All,

we  install fleet managenet devices in vehicles and sometimes connect its to the CAN system too. We need to keep the termination value on 120ohm. The device's installation manual offer to measure (with multimeter) the resistance between the CANL and CANH wires (without powering the CAN network; in general switch off the ignition). Depends on the measured value we have to swith on or off the device's termination resistor.
My question: if the CAN network consists one or two node with switchable termination resistor at the network's end, will the measurement (without
powering) shows the real network termination resistance? In case it won't shows the real value, is there any easy way to determine it?  (or I have to use scope to  evaluete the rise and drop edges?)

Thanks in advance: Tamas Hadarits
www.tachografszerviz.hu





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Archives and useful links: http://groups.yahoo.com/group/CANbus
Subscribe and unsubscribe at www.vector.com/canlist/ Report any problems to <[email protected]>
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Archives and useful links: http://groups.yahoo.com/group/CANbus
Subscribe and unsubscribe at www.vector.com/canlist/
Report any problems to <[email protected]>