Campbell Hausfeld SDM-CAN - Manual (Page 7)

Section 1. Introduction
The SDM-CAN interface is designed to allow a Campbell Scientific datalogger to sample data
directly from a CAN-Bus communications network and thereby allow such data to be stored
along with, and in synchronisation with, other data values measured directly by the
datalogger.
To use the SDM-CAN device it is assumed that you have a full working understanding of the
CAN network you wish to monitor. While there are moves to standardise CAN networks for
different types of applications, the SDM-CAN device is designed to be as generic as possible
thus allowing use in a wide range of applications, including research and development, where
you may be working outside the normal standards.
As a result you will need to know details of the electrical configuration of the network, the
speed and CAN standard in use, plus knowledge of the identifiers of the data packets that are
of interest and the way in which data is encoded within those packets at the binary level. This
information may need to be obtained from the designers of the network, from propietary
documentation or from the standards to which a network claims to comply.
Campbell Scientific cannot provide full technical support in the understanding and decoding
of data on all types of CAN networks.
Figure 1-1 SDM-CAN CAN-Bus Interface
1.1 General Description
The SDM-CAN forms an intelligent interface between a Campbell Scientific
datalogger and a CAN-Bus communications network. The SDM-CAN is
configured by the datalogger under the control of the user’s datalogger program.
By this process the SDM-CAN can capture data on the CAN-Bus and filter out
packets of interest to the user. Within each data packet the device is able to read
one or more data values and convert them to numeric values compatible with the
normal data stored by the datalogger.
The SDM-CAN will act as a passive listen-only device with its transmitter
disabled in hardware. Alternatively it can be configured to send/respond to
Remote Frame Requests, allowing it to poll remote devices for data. Data packets
can also be constructed to allow it to send data out onto the CAN-Bus so it then
acts as a sensor itself.
Data is transferred between the SDM-CAN interface and the datalogger using
Campbell Scientific’s high speed SDM communications protocol. This protocol
allows the SDM-CAN to be used in parallel with other SDM devices (including
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