The ten CAN commandments
- You shall read the manuals and publications of your components first.
- You shall use CAN cable with know parameters (data sheet).
- You shall use exactly 2 terminating resistors.
- You shall ground your network.
- You shall observer maximum lengths of trunk and drop lines. Wise man calculated it, believe.
- You shall mount a CANobserver, it will warn you on problems before the system breaks down.
- You shall avoid closeness to electrical jamming sources.
- You shall keep distance to high voltages.
- You shall avoid high common mode voltages.
- You shall buy a measuring device for physical layer, therefore you will know how your bus is doing.
Even if this sounds funny to you, these are the principles that let your system run hitch-free. Remember at buying a measurement device that only GEMAC tools are really measure at physical layer 1. Displaying an oscillogram only is not a physical measurement ! To rate an oscillogram is hard, even for CAN gurus, how should a now-and-then-user run a chance to find something helpful ? No way !
On the contrary the GEMAC tools (CANtouch and CAN-Bus Tester 2) not only showing a oscilloscope, they measure the critical values you cannot see and rate them. The general quality level is a mathematical value with shows at a glance how a node is doing.
Experts worldwide say that 95% of errors in fieldbus systems are problems on the physical layer. A fitting testing and measuring device together with the appropriate knowledge is the qualification for a quick and successful trouble shooting.
Why we point out that CANobserver ? The unit is undervalued – and yet it is a genius tool to monitor your CAN system. It detects errors and signal them – without you equipped with your laptop and measuring device. As soon as problems occur, the unit observe and signal it. The unit is not expensive, but if it is still too much, then install a CANalarm at minimum. Then you detect error frames and increased traffic load (clear signals for deeper problems) if they occur and you might have a chance to react before the systems stands still.