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CAN Bus Connector Requirements

Hardware: Industrial Communications>>CAN

Problem:
I am wiring my NI-CAN controller to a CAN bus; which pins must I consider?

Solution:
The CAN bus is often implemented with a DB-9 connector, however, not all 9 pins require wiring. More specifically, 3 pins define communication on the CAN bus and must be wired. They are (for NI-CAN products):

Pinout for 9-Pin D-SUb Connector

CAN_H: pin 7, which defines the higher potential line for the differential CAN bus.

CAN_L: pin 2, which defines the lower potential line for the differential CAN bus.

V-: pin 3, which defines the ground or return path for current driven by the differential bus; this pin must be connected to all CAN nodes since the CAN transciever measures CAN_H and CAN_L against this pin, and if floating can disturb communication.

Notes on the other pins:

  • Pin 6 is internally connected to Pin 3
  • Pin 9 is used to supply bus power to the CAN physical layer if external power is required. All High-Speed Series 2 PCI and PXI hardware is powered internally, so it is not necessary to supply V+, unless you have configured the VBAT jumper for EXT.
  • Pins 1, 4, and 8 are no connection pins; they have no electrical connection to the CAN board.
  • Pin 5 is an optional shield to be used with shielded cables; it can improve signal integrity by maintaining an electrical connection to the shield in the cable. NOTE: This is the only pin that isn't isolated from chassis ground but connected to it through a 10MOhms resistor and a 0.01uF capacitor in parallel (these are high voltage components). The D-Sub connector shield is connected to chassis ground directly.

For more information on CAN connectors and cables, including the combicon connector, see Chapter 4: Connectors and Cables in the NI-CAN Hardware and Software Manual linked in the related links below.

Related Links:
Product Manuals: NI-CAN Hardware and Software Manual and Specifications
KnowledgeBase 3IABNOHS: Proper Termination for NI-CAN Hardware (High Speed, Low Speed and Single Wire)


Attachments:
CanCable.jpg

Report Date: 04/11/2005
Last Updated: 03/31/2009
Document ID: 3KAH644B

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