The structure of the NMEA 2000 CAN Identifier is based on a similar structure as SAE J1939, where the arrangement appears as shown
in Fig. 6. Here it can be seen that the 29-bit CAN ID is sectioned (from
right to left) with one byte of Source ID (or node ID). The next two
bytes make up the PGN.
Fig. 6: NMEA 2000 CAN ID field.
Another display option of the X-Analyser is to view a display showing the
CAN ID broken down by PGN, Source
Address, Data Page, and Priority as
explained in Fig. 6. An example of this
display can be seen in Fig. 7.
Also, the selected signals (fields) can be
seen in this display. These were selected
from the NMEA 2000 CAN database
embedded in the X-Analyser. This database contains all the standard NMEA 2000
messages (PGNs) with their assigned data
according to the NMEA 2000 specification.
Another option of X-Analyser that
combines a 3-in-1 feature where all three
layers are considered is the PicoScope
option of X-Analyser. This is a future version of X-Analyser 3. As shown in Fig. 8,
we can see that the Data Link display is
combined with the Physical Layer display
at the bottom. Here we have highlighted
the Fluid Level message, which is PGN
F211 (the preceding 1 indicates the DP of
1), and source address of 70. The Physical
Layer component of this message is shown
at the bottom of this display. The CAN_H
is shown in blue, and the CAN_L in red.
The green waveform shows the differential
voltage relationship between CAN_H and
CAN_L. Also note that each component of
the CAN frame is highlighted within the
The 3-in-1 Analyser Concept
This display is useful for viewing the
physical integrity of the CAN frames. It
allows ease of selection of a NMEA 2000
message, and view it on all levels (
Application, Data Link and Physical Layers). In
troubleshooting, it can be instrumental for
seeing if there is too much noise disturbance on the wire. Also, “ringing” during
transitions of data can indicate terminator
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Fig. 7: X-Analyser view of the NMEA 2000 Application Layer.