SDO Construction Details
CANBus Networking Manual
39
SDO Construction Details
CANOpen SDO frames can easily be created manually and used to send commands
and queries to a Roboteq device. The directives below are a simplified description of the
CANOpen SDO mechanism. For more details please advise the CANOpen standard.
A CANOpen command/query towards a Roboteq device can be analyzed as shown below:
Header
DLC
Payload
Byte0
Byte1-2
Byte 3
Bytes4-7
bits 4-7
bits2-3
bits0-1
0x600+nd
8
css
n
xx
index
subindex
data
•
nd is the destination node id.
•
ccs is the Client Command Specifier, if 2 it is command if 4 it is query.
•
n is the Number of bytes in the data part, which do not contain data
•
xx not necessary for basic operation. For more details advise CANOpen standard.
•
index is the object dictionary index of the data to be accessed
•
subindex is the subindex of the object dictionary variable
•
data contains the data to be uploaded.
The Response from the roboteq device is as shown below:
Header
DLC
Payload
Byte0
Byte1-2
Byte 3
Bytes4-7
bits 4-7
bits2-3
bits0-1
0x580+nd
8
css
n
xx
index
subindex
Data
•
nd is the source node id.
•
ccs is the Client Command Specifier, if 4 it is query response, 6 it is a successful
response to command, 8 is an error in message received.
•
n is the Number of bytes in the data part, which do not contain data
•
xx not necessary for the simplistic way. For more details advise CANOpen standard.
•
index is the object dictionary index of the data to be accessed.
•
subindex is the subindex of the object dictionary variable
•
data contains the data to be uploaded. Applicable only if css=4.
SDO Example 1: Set Encoder Counter 2 (C) of node 1 value 10
•
nd = 1, since the destination’s node id is 1.
•
ccs = 2, since it is a command.
•
n = 0 since all 4 bytes of the data are used (signed32).
•
index = 0x2003 and subindex = 0x02 according to object dictionary.
