dataTaker CANgate, User Manual

Page: 10 / 42

UM-0086-A2
CANgate User’s Manual Page 10
Connecting to an Existing CAN Network
A typical CAN network might be wired as follows:
Typical layout of a vehicular CAN network
In this case the vehicle has five ECUs connected to the CAN bus, plus a diagnostic connector. ECUs 1 and 5 are at the ends
of the main bus, so they incorporate termination resistors. ECUs 2, 3 and 4 connect to the bus via short stub connections and
do not include a termination resistor.
Notice that CANgate incorporates
weak termination (2.6k Ω ). This value is high enough so as not to significantly increase
the DC load on the already terminated bus, yet low enough to provide some damping of reflections on CANgate's stub
connection to the bus. This allows the length of the stub to be extended to around 2-3 metres. Note that some of the ECUs
may also include weak termination to allow their stub connections to be extended slightly.
Connecting to a Single ECU
If CANgate is connected to a single ECU (eg for laboratory testing) then an external termination resistor may be required
Direct connection to a single ECU
In this case a short (1m) cable is used so the two 120 Ω resistors are combined into one 60 Ω resistor. If a long cable is used
then 120 Ω resistors should be placed at each end. This assumes that the ECU is not terminated (or weakly terminated). If
the ECU includes its own 120 Ω termination then an external 120 Ω resistor is only required at the CANgate end of the cable.
Note that if the cable is short and the bit rate moderate then you may well get away with no external termination, ie.
CANgate's internal weak termination may be adequate.
Inside CANgate
Accessing CANgate Internals
If it is necessary to alter the settings on the internal DIP switch then CANgate will need to be disassembled, as follows:
1. Disconnect any cables from the CANgate connectors.
2. Remove the two Philips-head screws on the right hand ("Host RS232") end of the case.
3. Remove the aluminium end plate and plastic surround.
4. Push on the connector at the other end of the case. The printed circuit board (PCB) should slide out.
ECU
CANgate
2.6 K
Ω
60 Ω
ECU 1
120
Ω
ECU 2
ECU 3
ECU 5
120
Ω
ECU 4
CANgate
2.6 K
Ω
DIAG PORT
CAN-LO
CAN-HI
stub stub
stub stub