7 — CANopen COMMUNICATIONS
Curtis Model 3150R – Oct. 2022
pg. 30
7 — CANopen COMMUNICATIONS
Model 3150R complies with the CAN in Automation (CiA) CANopen 301 specification. This chapter
describes the gauge’s CANopen features.
Some familiarity with CANopen is a prerequisite. For CANopen information, see the following pages
on the CiA web site:
• Overview:
https://www.can-cia.org/canopen/
• Specifications:
https://www.can-cia.org/groups/specifications/
BYTE AND BIT SEQUENCE ORDER
CANopen message byte sequences are transmitted with the least significant byte first (little-
endian format).
Note: This manual uses the LSB 0 Numbering convention when referring to byte and bit numbers.
For example, the following table shows an SDO that writes the data 04E2h to the object with the
index and sub-index 334C-01h:
0
1
2
3
4
5
6
7
Control Byte
Index
Sub-index
Data
2Bh
4Ch
33h
01h
E2h
04h
00h
00h
Strings are read from left to right. The following example shows how the 3150R transmits an SDO
segment for the string "Curtis":
0
1
2
3
4
5
6
7
Control Byte
Data
00h
43h = "C"
75h = "u"
72h = "r"
74h = "t"
69h = "i"
73h = "s"
Bit sequences are transmitted from most significant to least significant bit (big-endian format). The
following example shows how the gauge transmits the bits for the value 2Bh:
7
6
5
4
3
2
1
0
0
0
1
0
1
0
1
1
NODE IDs
Model 3150R’s node ID is specified with the CAN Node ID parameter. The default node ID is 0x2E.
The message center has its own node ID, which is specified with the Message Center Node ID
parameter. The message center’s default node ID is 0x50.
Note: Both parameters are on the
BAUD RATE
The gauge’s baud rate is specified with the CAN Baud Rate parameter on the CAN menu. The default
baud rate is 125 Kbps.
