Technical Knowledge

CANopen bus protocol message analysis
Release Date : 2020-07-01 11:11:20


There are two types of CANopen protocol analysis plug-ins in the CANPro protocol analysis platform. One is Block_CANopen, which is used to analyze CANopen protocol messages that support block transmission, and the other is CANopen, which is used to analyze CANopen protocol messages that do not support block transmission. For more CANopen protocols, please see CANopen bus protocol.




The reason for this distinction is that the block transmission message in the CANopen protocol is context-sensitive. To identify the block transmission message, you need to know the previously transmitted message information, but the CANPro protocol analysis platform only conducts the current CAN frame. Analysis, so it is impossible to identify the block transmission message, and the judgment based on the current CAN frame may mistake the block transmission message as other SDO messages.
 
Therefore, for the CANopen protocol that supports block transmission, when it encounters an SDO message, it only displays its node ID and data field, and no longer judges which type it belongs to in SDO. The CANopen protocol that does not support block transmission will recognize the specific type of SDO message.
 

The following is a detailed introduction to each type of packet in the Block_CANopen protocol:

 
1. NMT Error Control NMT error control message
(1) Node ID ID identification of slave node
(2) Node Status
 
2. Node Guarding Request Node guarding request message, used to obtain the status of the slave node
(1) Node ID ID identification of slave node
 
3. NMT Module Control NMT module control message
(1), NMT Command NMT command identification
(2) Node ID ID identification of slave node
 
4. SYNC message
 
5. EMCY emergency error message
(1), Error Code Error code of emergency message
(2), Error Register Error register of emergency message
(3) Manufacturer Specific Error code customized by the manufacturer
 
6. TIME time message
(1) Time stamp information in the Time Stamp time message has been parsed as time
 
7. PDO PDO message
(1), PDO Object PDO communication object
(2) Node ID ID identification of slave node
(3), PDO Data PDO object data
 
8. Remote PDO Remote PDO message, used to request PDO transmission
(1), PDO Object PDO communication object
(2) Node ID ID identification of slave node
 
9. SDO SDO message
(1), SDO Object SDO communication object
(2) Node ID ID identification of slave node
(3), Data Field SDO object data
 

The message definitions of CANopen protocol and Block_CANopen protocol are the same, only the interpretation of SDO messages is different from Block_CANopen, which will not be repeated here. The various SDO messages defined in CANopen protocol are as follows:

 
1. Initiate SDO Download Request
(1) Node ID ID identification of slave node
(2), Object Index object index value
(3), Object Sub-index object sub-index value
(4) Transfer Type indicates whether the transfer type is fast transmission or general segmented transmission
(5), Size Indicator indicates whether the message identifies the transmission volume
(6) The number of invalid bytes in the Bytes Not Data field is only valid for fast transmission
(7) The number of data bytes downloaded by Bytes Downloaded is only valid for segmented transmission
(8), SDO Data SDO data field, only effective for fast transmission
 
2. Initiate SDO Download Response
(1) Node ID ID identification of slave node
(2), Object Index object index value
(3), Object Sub-index object sub-index value
 
3. Download SDO Segment Request SDO segment download request message
(1) Node ID ID identification of slave node
(2), Toggle Bit trigger bit
(3), Whether More Segments mark is the last segment
(4) The number of invalid bytes in the Bytes Not Data data field
(5) SDO Data SDO data field
 
4. Download SDO Segment Response SDO segment download response message
(1) Node ID ID identification of slave node
(2), Toggle Bit trigger bit
 
5. Initiate SDO Upload Request
(1) Node ID ID identification of slave node
(2), Object Index object index value
(3), Object Sub-index object sub-index value
 
6. Initiate SDO Upload Response Initialize SDO Upload Response
(1) Node ID ID identification of slave node
(2), Object Index object index value
(3), Object Sub-index object sub-index value
(4) Transfer Type indicates whether the transfer type is fast transmission or general segmented transmission
(5), Size Indicator indicates whether the message identifies the transmission volume
(6) The number of invalid bytes in the Bytes Not Data field is only valid for fast transmission
(7) The number of data bytes uploaded by Bytes Downloaded is only valid for segmented transmission
(8), SDO Data SDO data field, only effective for fast transmission
 
7. Upload SDO Segment Request SDO segment upload request message
(1) Node ID ID identification of slave node
(2), Toggle Bit trigger bit
 
8. Upload SDO Segment Response SDO segment upload response message
(1) Node ID ID identification of slave node
(2), Toggle Bit trigger bit
(3), Whether More Segments mark is the last segment
(4) The number of invalid bytes in the Bytes Not Data data field
(5) SDO Data SDO data field
 
9. Abort SDO Transfer SDO transfer abort message
(1), SDO Object SDO communication object (is it Server or Client)
(2) Node ID ID identification of slave node
(3), Object Index object index value
(4), Object Sub-index object sub-index value
(5) Abort Code abort code, indicating the reason for transmission abort
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