USER'S MANUAL
CAN bus LCD Display
TRI66.003 ver 2
10 April 2011
4
CAN BUS
4.1
CAN NETWORK TOPOLOGY
The CAN bus is structured as a linear network, with short stubs branching from 'T'
connectors on the main bus backbone to each device. The CAN bus data lines
must be terminated at each end of the main bus with 120 ohm resistors between
the CAN-H and CAN-L signals.
In the range of Tritium EV products, including the WaveSculptor 200, EV Driver
Controls, and LCD display, the CAN connections are implemented with an 'in' and
an 'out' connector, therefore placing the 'T' on the device, resulting in a very
short fixed-length stub on the circuit board of each device. This is ideal from a
signal integrity and network performance point of view.
4.2
CAN WIRING
The CAN data lines (CAN-H and CAN-L) must be implemented with twisted-pair
wire for proper data integrity. The wire should have a characteristic impedance
of 120 ohms.
Power should also be provided along the CAN cable, ideally with another twisted
pair to minimise noise pickup. An overall shield can also be advantageous.
From a performance perspective, the optimal choice of cable is 7mm Devicenet
CANbus 'thin' cable, with 24AWG (data) + 22AWG (power) twisted pairs and a
braided shield. Using this cable will result in a robust installation. However, it is
not cheap, and using it for a large network with many devices will quickly add up
to a significant cost. It also presents a significant mechanical load on the
lightweight LCD display, and should be strain relieved close to the display.
For those on a budget, standard CAT5 network cabling (which has an impedance
of 100 ohms) can be used, but may become unreliable in longer networks or in
the presence of electrical noise from DC/DC converters and other electrical
devices in the system – use this type of cable at your own risk.
4.3
CAN CONNECTOR
The connector used on the LCD display, EV Driver Controls and other Tritium
devices is a 6-way 3mm pitch Molex MicroFit connector. The pinout is shown
below, as viewed from the wire side – as you would look at it while inserting
crimps. The colours shown match those in the standard DeviceNet CAN cabling
pairs.
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