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can_faq:problem_solving_questions [2018/08/21 23:08] (current)
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 +====== Problem Solving Questions ======
 +
 +Why is my CAN not working ? Here are some Problem Solving Questions
 +This page should help you to find out why your network is not working by providing questions. Answering these questions should help to find out what is possibly going wrong.
 +
 +  * Are there two 120 Ohm resistors across the bus at each end to terminate the network drivers? See [[CAN Cabling|CAN Cabling]] and DeviceNetCable
 +
 +  * Is there at least one other node on the bus? 
 +
 +  * Are both CAN transceivers (when there are only 2 nodes) fault tolerant? ​
 +
 +  * Are all the nodes CAN-A or are there CAN-B compliant devices?
 +
 +  * Are the grounds between nodes connected together?
 +
 +  * Are you using a Commercial Off The Shelf (COTS) dongle to listen in on the messages. In other words: "can you trust at least one member at the bus?".
 +
 +  * Are you using an CAN speed according your network cable length ? See [[CAN Cabling|CAN Cabling]]
 +
 +
 +
 +If you can't detect the problem, segment the CAN bus into small parts to isolate the problem.
 +Split the bus in the middle, then the side which caused the  problem again, and again - this is the fastest way to find the cause.
 +
 +
 +===== Collection of other hints =====
 +
 +For cabling problems [[http://​www.kfz-tech.de/​Engl/​CAN-BusF1.htm | this site ]] shows some signal screen shots for common problems. ​
 +
 +[[ http://​canbusacademy.com/​ | CANbus Academy]] has created a "**CAN bus Troubleshooting - Quick Reference**"​ which is available on [[http://​canbusacademy.com/​can-bus-troubleshooting-pdf-sheet/​ | request]]. This pdf contains some key test procedures to troubleshoot a CAN bus using a multimeter.
 +
  

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