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CAN and CANopen: ISO / OSI layer model and service-tool PCAN-USB

Article No: KA-01877
Version: 2.0
Subject to change without notice
The article shows some basic differences between CAN and CANopen. It also contains information about an "easy to use" service-tool for displaying or transmitting of CAN messages
Related Products
MLSE-0500A2TP0 MAGN.LANE SENSOR
MLS
OLS

Table of Contents

Difference between CAN and CANopen referring to the "Seven Layer Model"

CAN exclusively uses the lower ISO / OSI layers 1 and 2 and therefore has a standardized frame structure.
CANopen bases on CAN and additionally uses the higher layer 7 with standardized protocol structure. It also supports the "EDS" file, which makes the sensor integration much easier.
EDS = Electronic Data Sheet

 

Main differences between CAN and CANopen

 

CAN CANopen
Used ISO / OSI layers: 1 + 2 Used ISO / OSI layers: 1 + 2 + 7
No distinctive controller/device  command structure Controller/device network management state machine (NMT)
No EDS file EDS file support for user friendly integration using Object Dictionary
Fix process data User defined PD mapping supported
Fix transmission mode Selectable transmission modes available

Topology & bus termination

The CAN network is mainly set up as line topology with 120 Ohms termination resistors at both ends. Stub lines are permitted to a limited extent. 

 

Connection of sensors with respectively without stub cable

PCAN-USB adapter and PCAN-View software tool

For service purpose SICK offers a third party CAN/USB converter (PCAN-USB #6067651). Using this converter and the free software tool PCAN-view allows e.g. displaying, transmitting and recording of CAN messages, setting node-ID etc. of a sensor.

PCAN-View download: https://www.peak-system.com/PCAN-View.242.0.html?&L=1

Simply start PCANView.exe after having established a point to point CAN connection between sensor and PCAN-USB adapter. If having a sensor that automatically outputs process data after initialization, these data are shown in the upper receive window. It´s also possible to request additional sensor data by command.

 

Following examples for cyclic process data and acyclic service data refer to a SICK MLS Line guidance sensor with default settings:

  • Node-ID: 0x0A (=10 dec.)
  • Baudrate: 125 kbps
  • TPDO1 active -> time-controlled output of Track data and status

The MLS sensor cyclically outputs the process data by use of TPDO1 (Transmission Process Data Object). The standardized CAN-ID for TPDO1 consists of 0x180 + Node-ID (0x0A) resulting in 0x18A.

Acyclic service data

Acyclic service data are available by use of SDO request (ServiceDataObject). The standardized CAN-IDs for read request and read response are: 

Read request: 0x600 + Node-ID

Read response: 0x580 + Node-ID

Example for MLS sensor:
Read request and response for SDO Object 0x2024: Measured magnetic field strength in digits

Keywords:
mls, ols, canopen, iso, osi, layer model, PCAN, can, peak
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