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I am currently using a 4pin molex Microlock 1.25mm connector that has a CAN connection as well as a power connection.

pin 1 = power pin 2 = ground pin 3 = CAN_H pin 4 = CAN_L

We recently discovered an issue where if you wiggle the cable that is connected to the board connector, we can cause the CAN data to stop streaming (seems like a disconnection), we also see ESI hardware errors on the CAN packets we receive right before they stop streaming.

The interesting part is that the power and ground connections never drop as we have verified power passes through no matter what we do to the cable.

We are using CAN-FD at a bit rate of 5 Mpbs so it is definitely not a slow-speed data signal coming through.

I started looking at the connector and noticed we were using tin crimps on the cables. Many resources say that tin crimps will have a higher contact resistance after multiple cycles - however in our application we just insert the cable/connector a single time during the initial install.

Would switching to gold crimps provide better connectivity and help with this CAN dropout issue ? Is it possible the marginal increase in contact resistance can cause the CAN lines to stop transmitting ? The CAN cable that connects to this board is 2m long.

Looking for some advice before re-spinning these boards with different connectors.

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  • \$\begingroup\$ Done right, CAN is darned near bullet-proof. You can short the damned thing with a screwdriver (yes, that's exactly what we did to it) and still have it work. I've honestly no idea how you managed to make it sensitive to wiggling a cable. Find a better CAN driver IC would be my guess. The one you have isn't worth a darn. Hopefully, someone will have better advice. I worked with a designer in my case (I wrote software.) I was shocked at how well it worked. I mean that. It was stunning. But I don't know the hardware details, sadly. Someone here may fill in the details for you. I'm hoping! \$\endgroup\$
    – jonk
    Commented Aug 24, 2021 at 6:06

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I would think it is unlikely that this has anything to do with CAN and much more likely that this is related to the connector. These kind of fine pitch connectors aren't very reliable, especially not if you connect them multiple times. Could be crimping, wire damage, soldering or similar. It is a common issue that the cable wasn't attached 100% straight and centred. Another somewhat common problem is when you use too much solder and capillary force makes it wet upwards into the connector.

When you get the error, simply measure resistance from PCB to PCB. I'm pretty certain you'll find a short and not some issue with too high resistance.

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