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CAN bus physical layer diagnostics using onboard controllers

IP.com Disclosure Number: IPCOM000234607D
Publication Date: 2014-Jan-22
Document File: 3 page(s) / 23K

Publishing Venue

The IP.com Prior Art Database

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P22171: IP.COM

Abstract

The invention relates to a circuit for detecting CAN bus physical wiring condition. Finding a CAN bus wiring fault can be a very time consuming task, and require extensive knowledge of the vehicle wiring harness. During fault measurement, the master controller activates two relays, which are isolating the master controller itself from the bus lines that are being measured, and connecting CAN H line to a PWM high-side pin through a resistor and CAN L line to a PWM low-side line through a smaller resistor. From the voltage values of CAN H and CAN L, it is possible to interpret the fault on the CAN bus wiring.

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Page 01 of 3

Title: CAN bus physical layer diagnostics using onboard controllers


Abstract:
The invention relates to a circuit for detecting CAN bus physical wiring condition. Finding a CAN bus wiring fault can be a very time consuming task, and require extensive knowledge of the vehicle wiring harness.

During fault measurement, the master controller activates two relays, which are isolating the master controller itself from the bus lines that are being measured, and connecting CAN H line to a PWM high- side pin through a resistor and CAN L line to a PWM low-side line through a smaller resistor. From the voltage values of CAN H and CAN L, it is possible to interpret the fault on the CAN bus wiring.

Drawing:


Page 02 of 3

Description:

Currently, the CAN bus lines are typically connected to a controller's analog inputs, which typically have an input impedance of 100 K-Ohms. This is causing some disturbance to the CAN bus signals.

The circuit is utilizing the already existing machine controller I/O, namely the PWM high-side and low- side pins, and two relays. When the circuit is not active, it is not loading the CAN bus at all, and thus is not distorting the CAN bus signals, as the current implementations are causing.

When a measurement is being triggered, the control system master controller switches off all other controllers on the CAN bus.

The CAB controller performing the test will first isolate itself from the bus by activating the relay output. The relay will connect the CA...