The ten CAN commandments

  1. You shall read the manu­als and publi­ca­ti­ons of your com­pon­ents first.
  2. You shall use CAN cable with know para­me­ters (data sheet).
  3. You shall use exact­ly 2 ter­mi­na­ting resistors.
  4. You shall ground your network.
  5. You shall obser­ver maxi­mum lengths of trunk and drop lines. Wise man cal­cu­la­ted it, believe.
  6. You shall mount a CAN­o­b­ser­ver, it will warn you on pro­blems befo­re the sys­tem breaks down.
  7. You shall avo­id clo­seness to elec­tri­cal jamming sources.
  8. You shall keep distan­ce to high voltages.
  9. You shall avo­id high com­mon mode voltages.
  10. 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.

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