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There are two standards for DB9 pinouts when it comes to CAN bus.

This seems to be the industrial version. I've seen it in PLCs and VFDs.

  • 7 - CAN-H
  • 2 - CAN-L
  • 3 - GND
  • 6 - GND
  • 9 - VBAT

This seems to be automotive. The only place I have seen it is in OBD2 to DB9 cables.

  • 3 - CAN-H
  • 5 - CAN-L
  • 1 - GND
  • 2 - GND
  • 9 - VBAT

Where do these standards come from, particularly the automotive one? Looking at the CAN Arduino shield from seed studio and spark fun they have both pinouts and solder jumpers to switch between them.

vini_i
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  • My industrial company uses the first pinout you posted for a lot of different internal boards. I have also seen quite a lot of PC can interfaces with the 1st pinout. – MadHatter Jun 19 '20 at 21:50

2 Answers2

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"CAN in Automation" (CiA) is an association that tries to standardize CAN in industrial environments. They publish documents on various parts of CAN networks and CAN related protocols. An example:

CiA 303-1 version 1.9.0 Recommendation - Part 1: Cabling and connector pin assignment
Description This document provides device and network design recommendations for CANopen physical layer. Additionally, it provides the guidelines for selecting cables and connectors for use in CANopen systems.

Many of the documents published by CiA are downloadable from their web-site. Unfortunately, not all of them.

In an industrial environment, in my experience vendors of automation products usually stick to such documents, because they want to be compatible to other products.

Where the connector pin-out in the automotive world comes from, I do not know. My suspicion is, that one of the major vendors started in that way and the others simply followed. Maybe there is some standardization too, but I doubt that we are able to get access to such documents easily.

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In automotive every interface or other device with a DB9 uses 7 and 2 as well. Kvaser, Vector, Peak... all of it. Only some 2 bit chinesium from alibaba (like arduinos and pis) seems to have the infernal 3 + 5 non-standard for some reason.

Elektro
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  • Amazon and Ebay, can't find a 2,7 cable. I've checked literally over 100 different listings. – vini_i Dec 09 '20 at 21:06