ByunghyunKimTTEC4848: CAN-Multiplexing Worksheet

1. CAN Waveform on Oscilloscope
Range Rover 2001
A twisted wire pair is located near ABS hydraulic Unit.

CAN Waveform

Aliasing?

Distortion caused in analog-to-digital conversion by a too low rate of data sampling. For audio signals, it usually results in flutter (rapid change in the signal) and, for video signals, in stair steps-like jagged edges (called 'jaggies') that appear on an image of curved or slanted lines. Cured or subdued by anti aliasing techniques such as filtering or super-sampling.

When I see the clear graphs and changing lines which means not aliasing condition.

From using anti aliasing filter, I can see more clear graphs of CAN signals.

The main voltage of A waveform : 2.7v

Other voltage : Pull down 1.8v

The main voltage of B waveform : 2.4v
Other voltage : Pull up 4v
When the voltmeter is set on AC volts, I can see signal's switching which means the AC volts are pulled up and down more clear than DC volts.

2. Scan Tool Observations
Vehicle : Lange Rover 2001
Scan Tool : Autoboss

High CAN : For safety critical modules which need fast communication, such as ABS, TCM, ABS and ECU
Low CAN : For lower priority modules which can handle slower speed communication, such as Power window, alarm system and central door locks.
From using scan tool with the OBD2 connector, I could check switch operations of CAN system with the actuator contorl mode of the scan tool, such as power window and head light switch.

3. Wiring Diagram Exercise