MSc Disertation CANopen IO Card Implementation

7/29/2019 MSc Disertation CANopen IO Card Implementation

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Implementation of digital I/O module for

communication using CANopen protocol

A thesis submitted to Newcastle University for the degree ofMSc in Automation and control

In the Faculty of Science, Agriculture and Engineering

2010

Mosab Yaseen Mohammed Elamin

SCHOOL OF ELECTRICAL, ELECTRONIC AND COMPUTER ENGINEERING


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NEWCASTLE UNIVERSITYSCHOOL OF ELECTRICAL, ELECTRONIC AND COMPUTER ENGINEERING

I, Mosab Yaseen Mohammed Elamin , confirm that this report and the work presented init are my own achievement.

I have read and understand the penalties associated with plagiarism.

Signed: .......................................................Date: ...........................................................


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Abstract

Many industrial automation technologies were developed due to the great benefits of

adopting automation in industry, one of these techniques is remote digital Input/Output (I/O)

modules which is widely used with considerable success in automation applications.

These modules communicate with controllers in different types of communication

protocols; CANopen is a field bus protocol which proved to be reliable for more than fifteen

years in automation communication.

This project describes in details the steps of implementing digital I/O module with

CANopen in both hardware and software terms, the module has been tested and verified.


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ContentsAcronyms .................................................................................................................................................... vii

List of figures ............................................................................................................................................. viii

List of tables ................................................................................................................................................. ix

Chapter 1 ...................................................................................................................................................... 1

Introduction .................................................................................................................................................. 1

1.1 Automation methods ......................................................................................................................... 1

1.2 Benefits of DCS: .................................................................................................................................. 2

1.3 Smart solutions:...................................................................................................................................... 3

1.3.1 Intelligent instrumentation ............................................................................................................. 4

Advantages: ............................................................................................Error! Bookmark not defined.

Disadvantages: .......................................................................................Error! Bookmark not defined.

Recent trends: ........................................................................................Error! Bookmark not defined.

1. 3.2 Remote or field I/O: ..........................................................................Error! Bookmark not defined.

Advantages: ............................................................................................Error! Bookmark not defined.

Disadvantages: .......................................................................................Error! Bookmark not defined.

Recent trends: ...................................................................................................................................... 5

1.4 Communication protocols ...................................................................................................................... 6

1.4.1 Open System Interconnection (OSI) model: ................................................................................... 6

1.4.2 Standard Vs proprietary .................................................................................................................. 8

1.4.2.1 Proprietary protocols ............................................................................................................... 8

1.4.2.2 Standard protocols: .................................................................................................................. 8

1.4.3 Ethernet VS Field bus protocols ...................................................................................................... 8

1.4.3.1 Ethernet .................................................................................................................................... 8

1.4.3.2 Field bus protocols ................................................................................................................... 9

Chapter 2 ................................................................................................................................................ 11

CAN protocol: ......................................................................................................................................... 11

2.1 Historical background: ................................................................................................................. 11

Chapter 3 ................................................................................................................................................ 12

CANopen: ............................................................................................................................................... 12

3.1 Protocol structure: ........................................................................................................................ 12

3.2 CANopen properties:.................................................................................................................... 13

Chapter 4....................................................................................................................................................16

Hardware implementation.........................................................................................................................16

4.1 Implementation description..........................................................................................................16


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4.2 Overview of the microcontrlloer....................................................................................................16

4.2.2 ECAN module features........................................................................................................17

4.2.3 Module overview.................................................................................................................18

4.2.4 I/O ports.............................................................................................................................18

4.2.5 Data recieving ....................................................................................................................19

4.2.6 Data transmission...............................................................................................................20

4.2.7 Interrupt services.........................................................................................................,.....21

4.2.8 Data rate programming......................................................................................................22

4.3 MCP2551 CAN transciever.............................................................................................................23

4.4 Voltage regulator ..........................................................................................................................24

4.5 Printed Circiut Board.....................................................................................................................25

Chapter 5 ................................................................................................................................................28

Software..................................................................................................................................................28

5.1 Initialization..........................................................................................................................29

5.1.1 Node initilization..................................................................................................29

5.1.1.1 Oscillator initilization...........................................................................29

5.1.1.2 Node ID................................................................................................29

5.1.1.3 Heart beat cycle setting.......................................................................30

5.1.1.4 Port initialization.................................................................................30

5.2 CANopen initilization..........................................................................................................31

5.3 Infinite loop processing......................................................................................................33

5.3.1 Processing functions...........................................................................................34

5.3.2 PDO message recieving......................................................................................34

5.3.3 NMT message group..........................................................................................35

5.3.4 SDO messsage group..........................................................................................35

5.3.5 Object dictionary................................................................................................35

5.3.5.1 Object dictionary entry......................................................................35

5.3.5.2 Reading and writing functions of the dictionary................................37

5.3.6 Message transmission........................................................................................38


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5.3.7 DemoProcessEvents function.............................................................................38

5.3.7.1 Input port processing.........................................................................38

5.3.7.2 Output port processing......................................................................39

Chapter 6...............................................................................................................................................40

Tests......................................................................................................................................................40

6.1 Input port test....................................................................................................................40

6.2 State request test..............................................................................................................40

6.3 Output port test................................................................................................................40

6.4 Reading from and writing to object dictionary.................................................................40

6.4 Node state change command...........................................................................................40

Conclusion..........................................................................................................................................41

References:.........................................................................................................................................42


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Acronyms

CAN Controller Area NetworkCIA Control In Automation

CPU Central Processing Unit

CSMA/CD Carrier Sense Multiple Access

/Collision Detection

DCS Distributed Control System

IEEE Institute of Electrical and

Electronics Engineers

I/O Input/Output

ISO International Standardization Organization

MAC Medium Access Control

NCS Network Control System

NMT Network Management System

OPC Object Linking and Embedding;

(OLE) forProcess Control

OSI Open System Interconnection

PC Personal Computer

PCB Printed Circuit Board

PDO Process Data Object

PLC Programmable Logic Controller

SDO Service Data Object
http://en.wikipedia.org/wiki/Process_Controlhttp://en.wikipedia.org/wiki/Process_Control


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List of figures

Figure 1: Typical DCS system [7] ................................................................................................... 2

Figure 2: OSI model ........................................................................................................................ 6

Figure 3: Communication services required for DCS systems ....................................................... 7

Figure 4:CAN definition according to OSI model ........................................................................ 11

Figure 5: CANopen protocol mapped to the OSI model ............................................................... 12

Figure 6: state transitions for a CANopen node............................................................................14

Figure 7: pic18f2585 pin diagram.................................................................................................16

Figure 8: Module circuit layout.....................................................................................................24

Figure 9: Top layer tracks..............................................................................................................25

Figure 10: Bottom layer tracks......................................................................................................25

Figure 11: Top and bottom layers..................................................................................................26

Figure 12: Code flow chart............................................................................................................27

Figure 13: Initialization.................................................................................................................29

Figure 14:Infinite loop processing flow chart..............................................................................34


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List of tables

Table 1: Field bus protocols...........................................................................................................9

Table 2: Fieldbus protocols and key factors................................................................................10Table 3: CANopen characteristics................................................................................................13

Table 4: CANopen node states....................................................................................................14

Table 5: PIC18F2585 key features..............................................................................................17

Table 6: Comparison between CAN and ECAN modules..........................................................18

Table 7: Registers associated to receive buffers.........................................................................19

Table 8: Registers associated to transmit buffers.......................................................................20

Table 9: Interrupt registers.........................................................................................................21

Table 10: Bit timing controlling registers...................................................................................23

Table 11: MCP 2551 features.....................................................................................................24

Table 12: Dip switch and baud rates...........................................................................................30

Table 13: Messages groups values..............................................................................................32

Table 14: Messages numbers in message groups.....................................................;;.................32

Table 15: Node states and corresponding value in heartbeat messages......................................33

Table 16: node state change command values............................................................................35

Table 17: object dictionary structure and variable meaning.......................................................36

Table 18: object dictionary.........................................................................................................36

Table 19: transmit functions for message groups.......................................................................38

Table 20: PDO messages............................................................................................................41

Table 21: SDO messages...........................................................................................................42

Table 22: node state change command values...........................................................................43


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Chapter 1

Introduction

Automation is changing a process or a product to make it work in the best possible manner

without a significant human contribution. [1]

There exists the potential for much benefit and thus applying automation methods has

become important in all industries, some of the reasons are [1, 2]:

Replacing human man power in dangerous and hazardous fields.

Reducing costs in exchange for better product quality, less defective units, fasteroperations, and better utilization of raw materials.

The automation system provides information about processes, which allows defining

weak points and initiating possible improvements.

1.1 Automation methods

Three methods exist in automation:

Control boards for a specific unit.

Programmable Logic Controller (PLC) for a small scale process Distributed Control System (DCS) for a relatively large scale process [3]

Control boards: Early models of automation included the control board, which has a

number of switches, lights, analogue meters and other devices that inform an operator of a unit s

status [3].

PLC: Current models include PLCs, involving a processing unit controller. Under the

command of a set of operation conditions, PLC is operated to govern a sequence of processes[4]. It is often times used to control relatively small systems.

DCS: DCS: is a group of microprocessor based nodes connected in a network

(such as controllers, remote I/O modules, smart measurement devices or smart sensors).

DCS works with a central controlling unit and software packages, including archiving and

analysis tools connected through a communication network [5].

DCS (sometimes referred to as Network Control System (NCS)) was initially used with

industrial processes and factories. However, recently it has been utilized in numerous fields

including the likes of building automation, automotive systems, medical instruments ,airplanes,

amongst others[6], fig(1) [7] shows a typical DCS system, within which PLC and

control boards (machine controller) are labelled.


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Figure 1: Typical DCS system [7]

1.2 Benefits of DCS:

Enables efficient and easy analysis of the system based on data collected from monitoring

devices, this analysis allows improvements to be made to the process.

Increases the speed of failure detection in any device in the system allowing quick failure

detection and correction and in some cases without the need of human interaction.

Allows flexible operation by communicating and controlling all nodes inan acceptable time frame.


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Different control devices from different vendors can exchange data usingObject Linking and Embedding (OLE) for Process Control(OPC) server as shown in

figure(1), the OPC , is a set of standards used to enable plant real-time data

communication between control devices from different manufacturers[8].

It will be possible to connect industrial plants to the internet as shown in figure(1) which

can change the way of plant operation ,however this approach still needs greatresearch efforts.

Additionally [2]:

Since DCS uses a single data bus that connects all nodes, it reduces cost by decreasing

the number and/or length of connection cables.

It allows data buses to run long distances, thus increasing the coverage area.

Expanding DCS systems is easy as new nodes can easily be attached using extension

cable with appropriate communicating ports.

1.3 Smart solutions:Controlling units often connect sensors and actuators through I/O cards used for both

analogue and digital signals. These cards are mounted in the same rack within the cabinet of the

controlling units processor .Many wires connect the I/O cards with the instrument; nevertheless,

there can be some difficulties with this approach [9]:

If there are numerous instruments involved, then the number of wires can become

intolerable for the controller cabinet and difficult for the engineer involved. For large

number of instruments high rates controller processors are required to avoid operation

time delays due to processing time.

If the distance between the controller and instrument is elongated, then there is an excess

cost due to long cabling.

By being utilized for longer distances, the signal may be more vulnerable to noise signals

that can jam the data of interest. Moreover, cable losses may result in erroneous receipt.

It may be extremely difficult to install the processor in a field of harsh conditions

(high temperature, moisture, noise, or high level of gas emission).

Nodes can also be scattered far apart from each other requiring a standalone processor for

each set of neighbouring nodes.

For these reasons a new approach was developed to create moderate processing

capabilities in instrumentation. These new approaches enable a direct connection to data buses

in two different techniques:
http://en.wikipedia.org/wiki/Process_Controlhttp://en.wikipedia.org/wiki/Real-timehttp://en.wikipedia.org/wiki/Real-timehttp://en.wikipedia.org/wiki/Process_Control


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1.3.1 Intelligent instrumentation.

By adding a processor with a small sized memory in addition to built in communication ports to

instruments, dealing with superfluous wires can be avoided as only two communication wires

can connect all instruments in a multi drop fashion to the controller.

1.3.1.1 Advantages:

This technique overcomes the problem of noise picked up by connection wires as well as

power losses in long wires [10].

This unit performs initial processing including data conversion to engineering units, self

testing, initiating alarms according to set limits, or short term archiving. The unit aids

controllers by reducing processing loads [11]. The property of initiating alarms is

advantageous on event based maintenance where instruments can send alarms for improper

operation. These alarms allow maintenance staff to maintain devices before they completely

fail, and this saves money and time compared with cyclic maintenance. The possibility of remote configuration of instruments through data buses.

1.3.1.2 Disadvantages:

Intelligent instruments are more expensive than traditional ones.

With respect to different vendor instruments, interoperability should be considered.

1.3.2.3 Recent trends:

Many studies[12,13,14] support the wireless technology to be adopted in industrial

automation , by using sensors and actuators which communicate wirelessly with

controllers , in [13] the technology of Wireless Sensors Networks (WSN) is described.Standardization efforts are made by number of organization to define and implement

WSN however the real implementation still need time to spread, due to

some design challenges.

Advantages of WSN technology [12, 13]:

Reducing cabling costs

Flexible instruments distribution.

Some applications which require device mobility can be monitored and

controlled wirelessly [15].

Main challenges [12, 13]:

Noise signals.

Propagation losses.

Multipathing ( losses due to reflected waves from several paths).

Time delay, should be kept below certain limits.

Signal interference from other sources.


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1.3.2 Remote or field I/O:

Remote or field I/O (also known as smart I/O) is an input, output module installed remotely

with a low level of intelligence. Examples of intelligence include processing memory,

communication ports , and other physical ports to be connected to instruments.

1.3.2.1 Advantages:

This overcomes the problem of noise picked-up by connection wires as well as power

losses in longer wires.

And this unit makes initial processing such as data conversion to engineering units; this

serves controllers by reducing processing load.

Economically much better than the smart instrumentation approach.

1.3.2.2 Disadvantages:

Remote configuration for instruments is not possible.

More wires are required between instruments and Remote I/O.

Recent trends:

In [12] the Wireless Interface for Sensors and Actuators (WISA) technology is described, it

is adopting I/O modules which communicate with sensors and actuators wirelessly, having

nearly the same advantages and challenges described in 2.1.3 WSN technology.


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1.4 Communication protocols

1.4.1 Open System Interconnection (OSI) model:

The Open System Interconnection Reference Model is a general description of the

communication process by diving it to groups of services and putting these groups in a layer

form, fig (2) shows the OSI model.

This model was made by the standard International Standarization Organization (ISO) to

enable connectivity and interoperability between different vendors communication devices [16].

Figure 2: OSI model

Brief definition for each layer

Application layer: in this layer services of interacting with users are defined, includingapplication addressing, file transfer and others.

Presentation layer: in this layer the required data conversion, processing and encodingservices are defined.

Session layer: in this layer services are defined to link programs in the sending andreceiving devices along the network, it is not a physical link but it is a logical one.

Transport layer: the services here guarantee reliable transfer of a message no matterwhat size is it, over potentially unreliable networks.

Network layer: the services here define the communication path through a widenetwork connection.


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Data link layer: in this layer services responsible for four vital processes are defined,they are:

Error detection and correction: services detect and correcterroneous messages.

Flow control: these services manage the communication load between thetransmitter and receiver, for example if the receiver cant cope with the

transmission rate, these services will slow down the transmitter and buffer

the communication load.

Link management: these services deal with the sequence of rulesrequired for establishing connections between devices; there are certain

rules of communication: request from the transmitter and acknowledgment

from the receiver and some settings for request time out and other

parameters defined by these services.

Medium Access Control (MAC):Since all network nodes shares thesame bus or media , and at any time only one node should be transmitting

and the rest are either receiving or waiting , for a node to access the bus

(i.e. to get control on the bus and start sending) there are set of rules to

decide which node should take hold of the bus first, the services in this

sub layer decide that.

Physical layer: it is the physical interface between a node and the communication media,in here the transmitted signal physical properties are decided such as voltage levels,

power rates as well as physical port properties. Communication services required in DCS

are mainly in the application ,data link, and physical layers fig(3) shows an illustration of

the required layers in industrial applications; and more detailed description can be foundin [2,16].

Figure 3: Communication services required for DCS systems


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1.4.2 Standard Vs proprietary

A communication protocol is a set of rules governing transmission and receiving of data along with

defining physical properties of communication signals [17], many communication protocols has been

developed.

1.4.2.1 Proprietary protocols

In old DCS systems each company had special communication rules which are called

proprietary or private protocol ,vendors were providing a whole system for a factory or a

manufacturing line, i.e. all communication devices must be from only one vendor this has some

advantageous and disadvantageous [3]

The main advantage is that the system will be especially tailored to the factory so system

consistency and operability will be guaranteed.

Disadvantages:

Any system has some weak points, which do not exist in other systems, if designers have

the possibility to combine different systems, the overall results may be much better.

The customer will be restricted to one vendor in maintenance, spare parts and system

extensions, economically and practically this situation may cause difficulties.

1.4.2.2 Standard protocols:

Standard protocols published or approved by standard organizations and applied by large groupof vendors became more common, designers can select devices from different vendors and

connect them in one network, obviously a more flexible solution and also economically

effective because this standardization generates more competition between vendors allowing

lower prices for customers [6].

1.4.3 Ethernet VS Field bus protocols:

1.4.3.1 Ethernet

There are large numbers of communication standards, some recent studies in DCS system

suggested that in the future Ethernet (IEEE 802.3: Carrier Sense Multible Access (CSMA/CD))will dominate in industrial automation communication [18, 19]

This point of view is based on recent trends of adopting Commercial Off-The-Shelf

(COTS) technologies in DCS systems including Personal Computers (PCs) and Ethernet

networks due to its great achievements in data communication i.e. personal computers

networks[18]

Advantages of Ethernet:

Large capacity of data transmission.

Very high transmission rates.

Compatibility with data networks , this can be very useful, by using appropriate software,field information can be archived in the instruments or controllers, this information can

be send through automation network to the management ,financial, and marketingdepartments or even through internet.


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However Ethernet is not always the best solution in automation applications, because

originally data communication is different from control communication , Ethernet has high

data rates but there are problems with its transmission time determinism , depending on network

size and bus load, transmission time delays are small yet random, these delays have no effects

on data networks, but in automation, small delays in feedback control messages for examplemay result in unstable system. [6]

There are many efforts to improve Ethernet timing properties and to design new versions

called Real Time Ethernet RTE; now more than twenty approaches are available.

More over in some applications with short messages a field bus protocol

Controller Area Network (CAN) was found according to [6] to have better achievements.

This kind of messages is dominant in the lower level in control systems, the communication

between sensors, actuators and controllers, as well as embedded controllers industry like

automotive, medical instruments, aircraft industries and more.

In addition ,some field bus protocols currently have adopted Ethernet facilities such as

Foundation Field bus High Speed Ethernet FF HS1, Modbus TCP, and some others in the way

[12], moreover available in the market gateways between field bus and Ethernet, these gatewaysoffer transparent transmission of field bus protocols from point to point over Ethernet.

One disadvantage of using gateways is that, gateway circuits need time to process the data

flow, this will increase time delays.

1.4.3.2 Field bus protocols

Field bus protocols are a group of protocols for industrial automation, the term bus was

originated from the fact that all devices in the field (e.g. factory, manufacturing line, etc.) are

connected serially through cables, in early automation systems each manufacturer or vendor had

a special protocol, thats why large number of protocols are classified as fieldbuses these days

.Table (1) shows the most common field bus protocols , more information can be

found in[20].

Table 1: Field bus protocols

Field bus Name Technology Developer Year IntroducedProfibus DP/PA Siemens DP: 1994 PA: 1995Interbus Phoenix Contact Interbus Club 1984DeviceNet Allen-Bradley 1994Arcnet Datapoint 1977AS-I AS-I Consortium 1993Foundation Field bus H1 Fieldbus Foundation 1995

Foundation Field bus HSE Fieldbus Foundation2000

Seriplex APC 1990WorldFIP WorldFIP 1988LONWorks Echelon 1991SDS Honeywell 1994ControlNet Allen-Bradley 1996CANOpen CAN in Automation 1995

Modbus Plus Modicon -------

Modbus RTU/ASCII Modicon 1999


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Comparisons:It is not easy to compare between field bus protocols and decide which one is the best ; this

comparison depends on two issues ,technical specifications and economical feasibility.

First of all application type defines which protocols are applicable , some protocols are

widely used in large processing systems, but not used in smaller scale applications.

Key factors of technical specifications are: Maximum number of nodes in a network segment.

Maximum distance.

Data rate.

Maximum delay time and some other factors.Interestingly some studies [21], suggested an approach to compare protocols and the final

result is a quantitative figure, using a technique called entropy ideal point, this procedure

doesnt only consider technical specifications but also some economical aspects such as

System cost.

Installation cost.

Maintenance cost.However some important economical factors are not included which relates to the currentstatus of the customer such as

Training cost.

Replacement cost if required, and other factors.Still it is a wonderful approach; table (2) shows some field bus protocols

with key properties [20].

Table 2: Field bus protocols and key factors

Fieldbus Name Max Devices Nodes Max Distance

Profibus DP/PA 126DP:100-1,200m/segmentPA: 1,900m/segment

Interbus 512 400m/segmentDeviceNet 64 500mArcnet 255 400/2000 feetAS-I 32 slaves 100-300m

Foundation Fieldbus H1240/segment65,000 segments

1900m

Foundation Fieldbus HSEIP addressingessentially unlimited

100-2000m

Seriplex 500+ devices >500 feet

WorldFIP64 without repeaters 2 km

256 with repeaters 40 kmLONWorks 32,000 per domain 2000mSDS 64 nodes, 126 addresses 500mControlNet 99 250-1000mCANOpen 127 25-1000mModbus Plus 32 per segment, 64 max 500m per segmentModbus RTU/ASCII 250 per segment 350m

.


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Chapter 2

CAN protocol:2.1 Historical background:

CAN is an international serial communication protocol, standardized in ISO 11898-1 and

classified as a field bus, it was originally designed in BOSCH automotive company in 1980 to

achieve in-vehicles communication control, in instead of large number of wires, but after that it

found its way to other applications in industry [2].

CAN protocol only specifies the data link layer and physical layer as shown in fig (4).

Figure 4:CAN definition according to OSI model

There are collection of protocols related to CAN, they are

CAN Application layer CAL, CANopen, DeviceNet, and J1939[22]

CAN Application layer CAL.

CANopen an application layer over CAN bus applied in many automation fields, one of the bestProtocols used in embedded networks in many kinds of machineries especially in Europe.

DeviceNet is a communication protocol based over CAN bus and was developed by

Allen-Bradley Company and mainly used in process automation applications.

J1939 protocol: is an application profile based on CAN originally was developed for in-trucks

communication, after wards had been applied for other fields.

2.2 CAN bus properties: Deterministic i.e. the maximum delay time of transmission is fixed.

The highest priority node always gets hold of the bus first, thus critical nodes are not

affected by time delays. Easy to setup.

Relatively cheap.

Reliable, very effective in error detection and correction.

Was succeeded in dealing with harsh fields conditions in automobiles for long time.

Easy to upgrade[23]

2.3 CAN bus filtering:CAN bus is a message oriented protocol, , there is no sender id or receiver id in a CAN

message , all nodes detects every message on the bus , each node determines whether to

accept and process a message or not based on the message identifier , each message has an

identifier ,which is a particular value , to do this each node need to perform a message filtering,

there are two types of filtering:


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FULL CAN where message identifiers which the node should receive and process arestatically defined and stored in the node registers , this procedure is fast in processing and

requires smaller programs.

Basic CAN the node manipulates identifiers by software ,requiring larger code , and

some processing time but is more flexible than Full CAN method , more details aboutCAN protocol can be found in[2]

Chapter 3

CANopen:

3.1 Protocol structure:CANopen is a field bus protocol based on CAN bus as shown in fig (5).

Figure 5: CANopen protocol mapped to the OSI model

The reasons why CANopen and CAN dont have specification for four layers i.e.

presentation, session, network, and transport are [2]:

Presentation layer: this layer responsible for encoding data, in CAN there is a defined set of

data types so no need for data encoding or addressing.


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Session layer: CAN adopts real time communication, thus no need for this layer which is

responsible for creating logical links between receiver and transmitter for each

communication transaction.

Network layer: Network layer is responsible for internetworking communication, since in CAN

bus the network can not be such big and complex this layer is not needed.

Transport layer: again because the nature of real time communication and high reliability inCAN networks no need for this layer which deals with semi-unreliable networks.

3.2 CANopen properties:

Table (3) shows some characteristics of CANopen [20].

Table 3: CANopen characteristics

Technology developer CAN In automationYear introduced 1995

Openness 17 chip vendors,300 product vendors, open

Network topology Drop line

Physical media Twisted pair optimal signal & power

Maximum devices (nodes) 127 nodes

Maximum Distance 25-1000m depending on data rate

Communication methods Master/slave, peer-to-peer, multicast, multimaster

Transmission properties 10,20,50,125,250,500& 800Kbps,1 Mbps

Data transfer size 8 byte, variable

CANopen properties are flexible, different choices of data rates and distances are available,even for the limitation of 8 byte message in CAN, CANopen can send longer messages by

breaking a message down to 8 data blocks and recombine them again in the receiver, nodes

number is really competitive.

One of the most powerful characteristics of CANopen that it is an open software, this results

in more flexibility for designers , on the other hand the cost for installing is reduced .

More field bus protocols can be found in [6] to be compared with CANopen.

Control In Automation (CIA) organization, publishes device profiles for CANopen in

different industrial fields, there are many profiles for specific applications such as I/O modules,

train machines, building room control and more.

Profiles help designers to access devices functionalities using CAN bus [2], there are many

published device profiles and other new fields are in progress [22].

3.3 CANopen services:3.3.1 Object dictionary:

CANopen specification defines a data base in each node from which all node information can

be accessed through the network this data base is called object dictionary, each entry in the

dictionary is addressed by an index and sub-index.

3.3.2 Communication objects:

There are four types of communication objects ( messages with specific identifiers and formats)

in CANopen network

SDO Service data objects

These objects are used to read from or write in the object dictionary.


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PDO Process data objectsThese objects are used to transfer the process information e.g. the states of the outputs

inputs of the device.

NMT Network management objectsThese objects are used by the network master node to change the state of a slave node,

the node states defined in the standard are shown in table 4, and figure 6 shows thecommands used to change the states, these commands are sent through NMT objects.

Table 4: CANopen node states

State Communication capabilities

Preoperational SDO communication is

possible to read and write

from the object dictionary,

heart beat messages are sent,

no PDO messaging is

possible

Operational All messages are available

Stop Only heart beat messages are

available

Figure 6: state transitions for a CANopen node[27]


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Node guard or heartbeat objectsThese are two ways to make a CANopen node send a periodic signal in the bus , this

signal serves two purposes:

o This signal is a sign that the node is up and working.

o And it contains the current state of the node thus the network master will get acurrent view of the status of all nodes on the network.


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Chapter 4

Hardware Implementation

4.1 implementation description:

The module implemented in this project has the following features:

4 inputs and 4 output.

Node id programmable through dip switch.

Programmable baud rate through dip switch.

Asynchronous message sending in case of port change.

Immediate port change in case of receiving operation request.

Full can implementation.

Standard identifiers communication.

Power supply 24V DC.

Reading and writing to/from the object dictionary.

The mode of operation can be controlled

( stop , preoperational, operational, reset command).

Send a heart beat in 2000 ms periods.

4.2 Overview of the microcontroller

The microcontroller used in this implementation is PIC18F2585 which is part of the

PIC18F2585/2680/4585/4680 family , these devices combine high processing capabilities and

low prices, along with some enhanced functions in memory and communication ports which help

improving the over all performance, table 5 shows the main features of PIC18F2585, and figure

7 shows the PIC18F2585 pin diagram [24] .


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Table 5: PIC18F2585 key features

Manufacturer Microchip

Data EEPROM (bytes) 1024

RAM Bytes 3,328

Flash memory KB 48

CPU Speed

(Million Instructions Per Second )10

Embedded communication

controllerECAN

Temperature Range (C) -40 to 150

Operating Voltage Range (V) 2 to 5.5

Pin Count28

Figure 7 pic18f2585 pin diagram[24]

4.2.2 ECAN Module Features:

ECAN is an enhanced CAN module developed by Microchip , with ECAN there are more

resources available in terms of buffers and filters.

ECAN is fully compatible with legacy CAN modules table 6 shows a comparison between

CAN and ECAN modules :


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Table 6: comparison between CAN and ECAN modules

CAN ECAN

Number of filters 6 16

Message buffers 2 recieve + 3 transmit buffers 2 recieve + 3 transmit

buffers+6 programmable

buffers(can be programmed to

be either receive or transmit)

Processing time Much less

Code size Larger

ECAN module can be operated in one of these three modes:

Legacy mode (mode 0) in this mode the module will operate as an ordinary CAN module .

Enhanced Legacy (mode 1) operates with the enhancements enabled.

FIFO mode (mode2) in this mode 2 or more buffers can be used to form a FIFO First In

First Out buffer in which no one to one filter to buffer link is available , suitable for applications

requiring large data bursts handling.

ECAN (mode 1) module is recommended for CANOPEN networks which normally require

large number of message handling [25].

4.2.3 Module Overview

The module consists of protocol engine , memory buffers and special function registers that

control the data flow.

4.2.4 I/O ports

This microcontroller has three I/O ports PORTA PORTB and PORTC, each port has three

registers controlling the port operation:

PORT register which reads the level of port pins.

TRIS register used to define each bit of the port as an input or output, if a bit in this register is

set to 0 the corresponding bit in the port will operate as an output and if set to 1 the

corresponding pin will be an input.

LAT it is an output latch used as a second alternative for reading or writing the port value.

Each pin in the port is protected from Vs and Vg by diodes.


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4.2.5 Data receiving:

The microcontroller when connected to a network bus will load every message into a

temporary buffer called the MAB Message Assembly Buffer, the message id will be

compared with the filters, if the massage ID matches one filter then the data will be loaded to

one of the receive buffer for further processing, for each receive buffer there is a control register

RXBnCON in which the information of which filter enabled the reception of the message is

stored , the processor will be informed by an interrupt flag in PIR3 register see

(section 4.6 interrupt services ) table 7 shows the registers associated with a receive buffer.

Table 7: registers associated to receive buffers

No. Register name Description Function

1 RXBnCon (n=0 or 1) Receive buffer

control register

bits 0-4 shows which

filter enabled the

message reception

2 RXBnSIDL used If

standard identifiers

are implemented in

the network (n=0 or 1)

Recieve buffer

Standard Identifier

Low byte

The low byte of the

standard identifier is

stored here

3 RXBnSIDH used If

standard identifiers

are implemented in

the network (n=0 or 1)

Recieve buffer

Standard Identifier

High byte

The High byte of the


stored here

4 RXBnEIDL used If

extended identifiers

are implemented in

the network(n=0 or 1)

Recieve buffer

extended Identifier

Low byte

The low byte of the

extended identifier is

stored here

5 RXBnEIDH used If

extended identifiers

are implemented in

the network(n=0 or 1)

Recieve buffer

extended Identifier

High byte



stored here

6 RXBnDLC Recieve buffer data

length count

The data length in the

message received is

stored here


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7 RXBnDm (n=0 or 1)

(m=0 to 7)

Recieve buffer data Eight registers in

which the eight data

bytes of the message

can be stored

4.2.6 Data transmission

In case of transmission the data to be send is loaded to one of the transmit buffers , the

processor is informed by setting bit 3 of the transmit buffer control register , after the

transmission is successfully finished bits 2 and 3 in the PIR3 register see

(section 4.6 interrupt services ) will inform the processor that the transmit buffer is ready to be

reloaded, table 8 shows registers associated to transmit buffers.

Table 8: registers associated to transmit buffers

No. Register name Description Functions

1 TXBnCON (n=0 or 1) Transmit buffer n

control register

Bit7 is a transmit

buffer flag set when

the transmission starts

and is not cleared till

the transmission finish

Bit 3 Transmit request

status bit informing

the processor that the

data in the buffer is

ready to be sent,

cleared if the

transmission was

successful

2 TXBnSIDH (n=0 or 1) Transmit buffer n

standard identifier

high byte



stored here

3 TXBnSIDL (n=0 or 1) Transmit buffer n

standard identifier

low byte

The low byte of the


stored here


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4 TXBnEIDH (n=0 or 1) Transmit buffer n

extended identifier

high byte



stored here

5 TXBnEIDL (n=0 or 1) Transmit buffer n

extended identifier

low byte

The low byte of the


stored here

6 TXBnDm

(n=0 or 1)(m=0 to 7)

Transmitt data buffer Eight registers in

which the eight data

byte of the message

can be stored

7 TXBnDLC (n=0 or 1) Transmit buffer data

length count

The data length in the

message to be

transmitted is stored

here

8 TXERRCNT Transmit error count

register

contains a value of the

rate of transmission

errors , if it overflows

then the module will

enter bus off state

4.2.7 Interrupt services:

In case of receiving or transmitting a message interrupt scheme should be available PIR3

peripheral interrupt register 3 is responsible for raising the interrupt flag in case of a message

received or transmitted table 9 shows registers which deal with message communication

interrupts:


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Table 9: interrupt registers


1 PIR3 Peripheral interrupt

request register 3

Bit 3 and bit2 are set

to inform the

processor that the

transmission is

completed and the

number of the

buffer is ready to be

reloaded

Bit1 and bit 0 are set

to inform the

processor that a

message have been

received and by the

number of the buffer

2 PIE3 Peripheral interrupt

enable register

Used to enable or

disable interrupts

3 IPR3 Peripheral interrupt

priority register

Used to set the

priority of buffers

4.2.8 Data rate programming

This module can be programmed to operate in one of the eight baud rates defined in the

standard , all time parameters are defined in terms of a time quantity called Time quanta TQ,

The value of TQ is derived from the oscillator frequency and a programmable value called

baud rate pre scalar BRP (0-63) by equation 1

TQ = (2 * (BRP + 1))/oscillator frequency...................1

Each of the four bit time segments defined in CAN specification is defined in multiples of TQ

thus the bit time is calculated by equation 2

Bit Time= TQ * (Synchronization segment + Propagation segment +Phase segment1 + Phase segment2).......................2

Finally the baud rate is calculated by equation 3Baud rate = 1/Bit Time......................3


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Table 10 shows the three registers controlling these values.

Table 10: Bit timing controlling registers


1 BRGCON1 Baud rate control

register 1

Bit7-6 define the

value of

synchronization

segment

Bit5-0 define the

value of BRP


register 2

Bit 5-3 define the

value of phase

segment1

Bit2-0 define the

value of propagation

segment


register 3

Bit 2-0 define the

value of phase

segment2

4.3 MCP2551 transceiver

MCP2551 is a CAN transceiver, to raise the voltage level of the signals sent and to protect the

microcontroller from overvoltage in the bus, key features are displayed in table 11 [26]


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Table 11: MCP 2551 features

Manufacturer Microchip

Speed 1 Mb/s operation

Standard ISO-11898

standard physical layer

Voltage supply Max. 7 volts

Protection Protection against damage due to short-circuit

conditions (positive or negative battery voltage)

Protection against high-voltage transients

High noise immunity due to differential bus

implementation

Temperature ranges -40C to +85C

4.4 Voltage regulator

78l05 regulator is used to transform the 24 V DC supply to 5 volts.


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4.5 Printed circuit board:

For designing the PCB two software packages were used Multisim to draw the layout of the

circuit as shown in figure 8.

Figure 8: Module circuit layout

Ultiboardto specify the

Physical dimensions of the components.

The copper tracks on the two sides of the board. The vias (a via is a connection between the two sides of the board).

Figure 9 shows the top layer tracks, figure 10 shows the bottom layer tracks, and figure 11

shows the two layers.

U1

pic18f2585

1

2

3

4

5

6

7

8

9

10

11

12

13

14 15

16

17

18

19

20

21

22

23

24

25

26

27

28

U2

MCP2551

1

2

3

4 5

6

7

8

J2

DSUB9F

R1

1k

R2

1k

R3

1k

R7

1k

R10

1k

R4

1k

R5

1k

R6

1k

R8

1k

R9

1k

J1

HDR1X2

R11

10.0k

J6

C1

15pF

2%C2

15pF

2%

X120MHz

U378L05

LINE VREG

COMMON

VOLTAGE

J3

HDR1X4

J7

HDR1X5

J4

HDR1X5

J5

R12

1k

R13

1k

J8

HDR1X6

J9

HDR1X2

J10

HDR1X2

J11

Key = SpaceR14

390

R15390

C3

330nF

2%

C4

0.01F

2%LED


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Figure 9 Top layer tracks

Figure 10 Bottom layer tracks


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Figure 11 Top and bottom layers


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Chapter 5.

Software

Microchip developed a CANOPEN stack [27] that includes most of the functions defined by

the standard, these functions need to be tailored for the application required, and most of these

functions were used in this project to program the microcontroller.

The program developed in this project handles both CAN and CANOPEN functions along

with continuously monitoring the input ports for any change, a description of the code in general

is introduced first , details for each service are mentioned afterwards.

Figure 12 shows a flow chart of the code.

Figure 12: Code flow chart

Power on

Continuous

monitoring

Processing

Change

detected?

Initialization

NO

Yes


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5.1 Initialization:

Module initialization consists of two parts as shown in figure 13.

Figure 13: initialization

5.1.1 Node initialization:

In this stage the oscillator and timer setting, node ID and baud rate are determined

dip switches are used for this purpose, and the ports are initialized according to requirements.

5.1.1.1 Oscillator initialization:

Since there are several options for the oscillator source in PIC18F2585 either internal or

external and different frequencies can be selected , in this mode the source of oscillator and

frequency value are selected.

The mode selected here is HS High speed external oscillator for this the register config1H was

set to 0b00000010 and the frequency 20 MHZ.

5.1.1.2 Node ID:

For node id 3 bits from port A were used to be connected to the 4 way dip switch (only

three ways are used and one reserved) , in initializing these pins must be configured as in puts

thus register TRISA see( section 4.1.4 ) is set to TRISA=0xFF; ( the rest of the pins are set as

inputs but are not used , still they are connected to a header for future use).

As per the standard it is not allowed for a node to have an ID of 0, thus a conditional

statement has been put in the code to avoid this

if(node0 == 0) node = 1; else node = node0;

mCO_SetNodeID (node) // Set the Node ID

Initialaization

Node

initialization

CANOPEN

initialization


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Similarly for baud rate two pins of PORTB are connected to a two way dip switch ,thus

PORTB is set to operate as an input port TRISB= 0xFF , the dip switch enable the operation in

one of four rates(1 Mbit, 500Kbit, 250Kbit,125Kbit per second) , in fact CANbus standard

defines eight rates , the remaining four are (800Kbit,50 Kbit,20Kbit, 10Kbit per second) but

because of the tester used in our case here for testing this module see( section ) only the above

mentioned rates are available.

For each dip switch selection the registers BRGCON1 BRGCON2 and BRGCON3 are set to

yield one value as shown in table 12.

Table 12: dip switch and baud rates

Dip switch value Registers values Baud rate

0 BRGCON1 = 0x00

BRGCON2 = 0x92

BRGCON3 = 0x82

1Mbit

1 BRGCON1 =0x01

BRGCON2 = 0x92

BRGCON3 = 0x82

500kbits

2 BRGCON1 = 0x03;

BRGCON2 = 0x92

BRGCON3 = 0x82

250kbits

3 BRGCON1 = 0x07

BRGCON2 = 0x92

BRGCON3 = 0x82

125kbits

5.1.1.3 Heart beat cycle setting

The heartbeat rate set in this stage , defining the cycle in milliseconds , by this function

mNMTE_SetHeartBeat (cycle), whereas cycle is in milliseconds.

5.1.1.4 Port initialization:

In this implementation PORTC pins 0-3 are used as inputs and PORTC pins 4-7 are used as

outputs , thus TRISC=0x0F.

There are two variables defined to store ports values:


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uLocalRcvBuffer to store the data received by messages to deal with output port PORTC 4-7.

uLocalXmtBuffer to store the state of the input port PORTC 0-3 to be send to CAN bus.

change is used to detect any changes in the input port.

These variables are set to zero in this initialization stage..

Since the standard defines message identifiers to include the node id:

PDO transmit id and PDO receive id are defined in this stage by the following

PDO transmit cob id is 384+node id which is the equivalent of 0x180+ node id.

PDO receive cob id is 512+node id (0x200+node id).

PIC18F microcontrollers are designed to handle identifiers in a reverse order, the id of

0b10001110 is handled with filters in this order 0b01110001 , so any id must be stored in

microchip format.

This is what the function mTOOLS_CO2MCHP (CO_COB) do, converts the MCHP COB

format to the CANopen format.

5.2 CANOPEN initialization

In this stage the CANOPEN services are enabled by these functions

_CO_COMM_NMT_Open (); Starts network management

_CO_COMM_SDO1_Open (); Starts the default SDO

_CO_COMM_NMTE_ Open (); Starts the heartbeat

_CO_COMM_PDO1_Open (); Start the pdo1

In this function there are another two functions:

The first one is mTOOLS_CO2MCHP which is responsible for setting the cob id for the

end point and transforming it from CANopen format to Microchip format

The second function is mCANOpenMessage this function uses a variable called handler ,

each end point has its own handler , addressing endpoints with handlers improves the data flow

and speeds up the message processing, messages are classified to three major groups:

Network control message group

SDO message group

PDO message group


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Each group is assigned a value as shown in table 13

Table 13: messages groups values

Message group Name value

Network control COMM_MSGGRP_NETCTL 0x00

SDO COMM_MSGGRP_SDO 0x40

PDO COMM_MSGGRP_PDO 0x80

Each group includes number of messages as shown in table 14.

Table 14: messages numbers in message groups

Message Message value Message group

COMM_NETCTL_NMT 1 COMM_MSGGRP_NETCTL

COMM_NETCTL_NMTE 4 COMM_MSGGRP_NETCTL

COMM_SDO_1 0 COMM_MSGGRP_SDO

COMM_PDO_1 0 COMM_MSGGRP_PDO

Thus each message is uniquely addressed by the group number and subgroup number e.g.

PDO1 is addressed by 0x80 and 0 and so on.

mCANOpenMessage function has two inputs and one return value:

mCANOpenMessage (MsgTyp, COBID, hRet)

MsgTyp= message type which is the group number in binary digitally (ored) with subgroup

number e.g. PDO1 message type = 0x80 | 0 = 0x80 and so on.

COBID is stored in a buffer _uCANRxIDRes[n], after wards this buffer is copied to filter

register RXFnSIDH (n= 0 to 15 in ECAN mode1)

hRet is a handle which indicates that the COBID was copied to one filter register.

Then the function mCANOpenComm is called to put CANCON register to zero,

CANCON CAN control is a special register in PIC18F2585 which is used to set the status of

the CAN controller in one of the following modes

Configuration mode

Listen only mode

Loopback mode

Disable mode

Normal mode


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CANCON=0 will put the controller to normal mode.

According to the standard a CANOPEN node should send a message informing the network

that the node has initialized, this message is called boot up message, and the COB ID for this

message is the same of heart beat with one data byte containing zero value.

This message is sent using the function of_CO_COMM_NMTE_TXEvent.

mCANSendMessage function is used to inform the processor that a message is ready to be

sent.

Then the node will enter preoperational mode as described by the standard , where the heart

beat message will be send every N milliseconds (N is decided by the programmer) with the

COB ID of 0x700 + Node ID with one data byte , this byte shows the state of the node as shown

in table15.

Table 15: node states and corresponding value in heartbeat messages

Data byte value State Communication capabilities

0x7F Preoperational SDO communication is

possible to read and write

from the object dictionary,

heart beat messages are sent,

no PDO messaging is

possible

0x05 Operational All messages are available

0x04 Stop Only heart beat messages are

available

5.3 Infinite loop processing:

Figure 14 shows the data flow chart after initialization, which is implemented by an infinite

loop while (1), as long as the node is powered this loop should be followed.


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Figure 14: infinite loop processing flow chart

5.3.1 Processing functions:

_CO_COMMRXEventManager this function deals with all received messages

In this function bit1 of register PIR3 is continuously monitored if it raises then this function

forwards a handle of the associated buffer , this handle is checked to determine which group this

message belongs to , then the relevant receiving function is called,

5.3.2 PDO message receiving.

For PDO group then the function _CO_COMM_PDO1_RXEvent is called , this function will

store the data field and data length in buffers for further processing.

After that the function mCANReadMessage is called to reset bit7 (RXFULL) of the buffer to

indicate that the message was successfully received.

5.3.3 NMT message group

For a state change command which belongs to NMT group the function

_CO_COMM_NMT_RXEvent is called, This function will check first that the data length is 2

Then it reads data byte zero , according to the value the node state

will change as shown in table 16.

Continuous

monitoring

Processing

Change

detected?

NO

Yes


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Table 16 : node state change command values

Data bytre0 value The state Functionality available

0x01 Start node , operational mode All messaging is available

0x02 Stop node No communication except

the heart beat

0x80 Preoperational mode SDO messaging and

heartbeat only

0x82 Reset communication The node will restart as if it

was powered off and

powered on again

5.3.4. SDO message group

For SDO messages then the function _CO_COMM_SDO1_RXEvent is called to determine

whether the message is an upload or download and respond accordingly.

5.3.5 Object dictionary

5.3.5.1 Object dictionary entry

The implementation of the object dictionary is achieved through using structures , each entry

in the dictionary is represented by a structure that contains all necessary information.

typedef struct _DICTIONARY_OBJECT_TEMPLATE

{

unsigned int index;

unsigned char subindex;

unsigned char ctl;

unsigned int len;

rom unsigned char * pROM;

}DICT_OBJECT_TEMPLATE;

Table 17 shows the function of each variable in the structure, and table 18 shows the object

dictionary implemented by this code.


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Table 17: object dictionary structure and variable meaning

Variable Function

Ctrl a variable that defines whether the entry is

writable or readable both

Len the length in bytes of the object

* pROM a pointer to the object

Table 18: object dictionary

Index Sub-

index

Object R/W Meaning

0x1000 0 Device type R Contains a code that

represent the type , reading

this value will return

0x111111

0x1017 0 NMTE_HeartBeatAccessEvent R This entry allows reading

the heart beat message

cycle

0x1018 4 Device serial number R Reading this object will

return device serial number

0x87654321

0x1200 1 SDO1_CS_COBIDAccessEvent R Reading this entry will

return the Client to Server

COB ID 0x600+node ID

0x1200 2 SDO1_SC_COBIDAccessEvent R Reading this entry will

return the Server to client


0x1400 1 RPDO1_COBIDAccessEvent R Reading this entry will

return the Recieve PDO

OB ID 0x200+node ID


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0x1600 1 RPDO1Map R Reading this entry will

return the index and sub-

index of the object that

store the data sent by

RPDO

0x62000

0x1800 1 TPDO1_COBIDAccessEvent R Reading this entry will

return the Transmit PDO


0x1800 2 TPDO1_TypeAccessEvent R Reading this entry will

return the Transmit PDO

type 255

0x1A00 1 TPDO1Map R Reading this entry will

return the index and sub-

index of the object that

store the data sent by

TPDO

0x60000

0x6000 0 uLocalXmtBuffer R Reading this entry will

return the state of the input

ports PORTC bits 0-3

0x6200 0 uLocalRcvBuffer R/W This entry allows reading

and writing to the output

ports PORTC bits 4-7

5.3.5.2 Reading and writing functions of the dictionary

There are two functions to access the dictionary:

_CO_DictObjectRead this function is used to read from the dictionary which in turn

manipulate two functions

CO_MEMIO_CopyRomToRam used if a data stored in ROM

need to be read .

CO_MEMIO_CopySram used for reading from RAM.


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_CO_DictObjectWrite this function is used to write in the dictionary ,in this function

only CO_MEMIO_CopySram is used, because it is not possible to modify ROM contents

in the run time.

5.3.6 Message transmission

_CO_COMMTXRdyEventManager() , this function is where all transmission requests are

dispatched , this function is continuingly checking these flags, each group has a variable called

transmit flag as shown below

COMM_NETCTL_TF Network control Transmit Flag

COMM_SDO_TF SDO transmit flag

COMM_SDO_TF PDO transmit flag

Whenever a message is ready to be sent the corresponding flag is raised , once one flag is

raised the associated transmit function is called, table 19 show the transmit function of each

group

Table 19 transmit functions for message groups

Message group Transmit function

NMTCTL _COMM_NMTE_TXEvent

PDO _CO_COMM_PDO1_TXEvent.

SDO _CO_COMM_SDO1_TXEvent

All these functions operate in the same way, they all set COBID , data length and put the

required data into the data filed of the message.

5.3.7 DemoProcessEvents function:

This function is the application defined and it has two parts:

Part 1 dealing with the input port.

Part 2 dealing with the output port.

5.3.7.1 Input port processing

The function keeps reading the input port (PORTC 0-3) storing the port value in a variable

called uLocalXmtBuffer and comparing this variable with the last state stored in the variable

uIOinDigiInOld , once a change is detected that means at least on pin was changed , then the

transmit flag of PDO1 is raised, there is a pointer linking the variable uLocalXmtBuffer with


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the transmit buffer thus when the transmit flag is raised the contents of uLocalXmtBuffer will be

sent , the stored state is updated to have the latest values , and the comparison starts again.

5.3.7.2 Output port processing

There is a pointer linking the variable uLocalRcvBuffer with the receive buffer, thus when a

PDO message is received the data field will be copied to this variable.

In addition LATC which is the value of the output port is assigned to uLocalRcvBuffer

(since PORTC0-3 are programmed as inputs only PORTC4-7 will change with LATC)

Thus any value sent in byte 0 of a PDO message will be forwarded to LATC4-7, also it is

possible to change the output port status through writing in the object dictionary.


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Chapter 6

Tests

The monitor software used is CANbus demo board [28] which include two CAN nodes each

is equipped by USB board that can communicate with a PC and display CAN messages in the

associated interface, the masks of these nodes are all set to one to enable receiving every CAN

message in the bus , the interface allow to form and send CAN messages as well.

6.1 Input port test

According to the implementation if one input changed state then an asynchronous PDO

message will be sent with the current state of the switches.

The COB ID should be 0x180+node ID; the first byte in the data field will reflect the state of the

inputs as shown in table () , if an input is connected then the corresponding bit should be one ,

otherwise should be zero, the test was successfully completed.

6.2 Output port test

A message is sent to trigger a signal through output port.

The COBID should be 0x200+node ID , byte0 of the data bytes should have the state

requested on the output port , for every bit set to one in bits4-7 in byte0 the corresponding port

should forward five volt signal , making the connected LED lit .

The test was successfully done as shown in table()

Another way is to lit the LEDs by writing in correspondent object in the object dictionary , this

was done as well as shown in table ()


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Table 20 PDO messages

6.3 Reading from object dictionary test:

Reading any entry in the object dictionary, this was successfully done as shown in table 21

Message

identifier

Data

length

D0 D1 D2 D3 D4-D7

Transmit PDO

Input port

change

0x180 +

node ID

8 Bits 0-3 the 4

ports status

00 00 00 00

Receive PDO

Output signal

command

0x200 +

node ID

8 Bits 4-7 the value

for each port

0x01 firs port0x02 second

0x04 third

0x08 forth

And combinations

e.g. value 0xC

means port3 and 4

00 00 00 00


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Table 21 SDO messages

6.4 State request test

The state of the inputs should be read on request, by reading the value of the input port from

the object dictionary the test was successfully completed .

Message

identifier

Data

length

D0 D1 D2 D3 D4-D7

Read from the

dictionary

0x600+

node ID

8 0x40 Index

low

Index

high

Sub

index

zeros

Read response 0x580+

node ID

8 0x43 for

four bytes

object

0x47 forthree bytes

objects

0x4B for

two bytes

object

0x4F for

one byte

object

Index

low

Index

high

Sub

index

The object

D7 most

significant

D4 least

significant

Write to the

dictionary

0x600+

node ID

8 0x2F

(for one

byte only)

Index

low

Index

high

Sub

index

D4 the data

to be

written

Write response 0x580+

node ID

8 0x60 Index

low

Index

high

Sub

index

zeros


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6.5 node state change commands:

These commands were successfully tested as shown in table 22.

Start remote node

Stop remote node

Enter preoperational mode

Node reset

Table 22 node state change command values

Message

identifier

Data

length

Data

bytre0

value

Data

byte1

value

The state Function Response

0x01 02 0x01 Node ID Start node ,

operational

mode

All messages are

available

The heart

beat data

byte 0 is

0x05

0x01 02 0x02 Node ID Stop node No

communication

except the heartbeat

The heart

beat data

byte 0 is0x04

0x01 02 0x80 Node ID Preoperational

mode

SDO messaging

and heartbeat

only

The heart

beat data

byte 0 is

0x7F

0x01 02 0x82 Node ID Reset

communication

The node will

restart as if it was

powered off and

powered on again

The boot up

message

will be sent

again data

byte 0 is 0


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Conclusion

The field of Industrial automation is developing rapidly , new technologies have appeared to

reduce costs and to increase efficiency in industry ,recent trends in automation are to useintelligent and wireless instruments , some researchers are even working to make

communication with DCS systems through internet a safe and feasible solution ,in this field

Remote I/O modules with CANopen have competitive characteristics.

In this project the implementation for digital I/O module has been described in details in

terms of hardware and software, and finally the module has been successfully tested.


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MSc Disertation CANopen IO Card Implementation

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