EATON
VFX Product Family Installation and Operation Manual E-ELCL-II003-E1 October 2014
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VFX Product Family
14.6
CAN & SAE J1939
•
Each device added to the J1939 manager
represents a physical device on the bus.
•
So a "local device" represents the local mobile controller. This is
the message the controller will be *transmitting*. See the "local
device" checkbox in the general tab.
•
A non-"local device" represents a physical device on the bus. Thus
its "Tx Signals" are what the device is sending and the mobile
controller is received.
•
Thus you should generally add one "device" to the tree to
represent each device that is on the physical bus, including the
"local" device.
•
Also make sure you have the "local device" checked for the node
that you want to be transmitting signals. While this is not intuitive
at first, it makes complete sense once you are aware of it.
•
There are no function blocks and everything
happens automatically in the background.
You just get scaled variables you can read or
write from code.
•
All transmission happens automatically
per the configuration for each PGN. The
"TransmissionMode" tab specifies the interval.
Relevant options are "Change of State" and "Cyclic",
but the default is change of state so the packet will
not be sent unless one of the variables changes
(i.e. from your code). Cyclic is the more traditional
J1939 method and better for testing.
•
The "I/O" mapping tab represents all the variables
available in the device. These can be used in code
for either inputs or outputs depending on whether
it is a transmitted or received packet.
•
You can automatically convert and scale variables
by clicking on the SPN in the "Tx Signals" page, and
then enabling the "Conversion" option. This lets
you deal in engineering units (i.e. %, rpm, mph,
etc) as opposed to the raw data bytes.
•
Variables in the I/O mapping tab will not be
updated unless physically used in code. This is an
optimization done by the 3S compiler to reduce
computation for unused variables. For debugging,
you can check the "Always update variables" box
and it will instruct the compiler/debugger to always
display and update the values.
•
The CAN "Network" option is base-zero. Thus
Network 0 represents the first CAN bus, Network
1 represents the second CAN bus, and Network 2
represents the third.
