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ObjectDictionary

Every CANopen node has an ObjectDictionary. An ObjectDictionary consists of Entries with a given index between 0 and 0xFFFF. An entry may also have a subindex for some specific CANopen types like RECORD or ARRAY types. This subindex must be between 0 and 0xFF. All of this information is stored inside of an EDS file as defined by CiA. This library can parse a standard EDS file and create the corresponding CANopen objects (SDO, NMT, etc...).

Basic Usage

To create an ObjectDictionary directly :

import "github.com/samsamfire/gocanopen/pkg/od"

odict := od.Parse("../testdata/base.eds", 0x20) // parse EDS for node id 0x20
The node id is required but is only useful when the EDS uses the special variable $NODE_ID. Usually, the ObjectDictionary is created when adding / creating a node on the network. Accessing OD entries and subentries directly is possible either by name or by value.

odict := od.Parse("../testdata/base.eds", 0x20)
odict.Index(0x201B) // get entry index by value
odict.Index("UNSIGNED64 value") // accessing with the actual name is also possible
odict.Index(0x201B).SubIndex(0) // returns the associated Variable object (for VAR types, subindex is always 0)
odict.Index(0x1018).SubIndex(1) // access sub-object of array

It is also possible to create new dictionary entries dynamically :

odict.AddVariableType(index, indexName, od.DOMAIN, od.AttributeSdoRw, "") // add a DOMAIN entry, and returns it
odict.AddVariableType(0x2500, "a number", od.UNSIGNED32, od.AttributeSdoRw, "0x1000") // add an UNSIGNED32 entry, readable and writable
record := od.NewRecord()
record.AddSubObject(0, "sub0", od.UNSIGNED8, od.AttributeSdoRw, "0x11")
odict.AddVariableList(0x3030, "record", record) // add a RECORD entry

Some more complex objects can be created dynamically, currently only a few are supported :

odict := od.Parse("../testdata/base.eds", 0x20)
odict.AddRPDO(1) // adds an rpdo object to EDS. i.e. new communication param at 0x1400 and mapping param at 0x1600
odict.AddTPDO(1) // adds a tpdo object to EDS. i.e. new communication param at 0x1800 and mapping param at 0x1A00
odict.AddSYNC() // adds sync object as well as extensions (1005,1006,1007,1019)
Note that currently adding these objects will not update the underlying EDS file on the system, meaning that downloading EDS through object 0x1021 for example will still return the original EDS file.

A default CANopen EDS is embedded inside of this package. It can be useful for testing purposes, and can be used like so :

odict := od.Default() // this creates a default object dictionary with pre-configured values

Exporting

Exporting OD to an EDS file is also possible. OD can be exported with default or current values.

    od.ExportEDS(odict,true,"path_to_exported.eds")

Special entries

CiA 301 defines a certain number of CANopen communication specific objects inside the object dictionary. These objects are inside of the Communication Profile Area and range between 0x1000 - 0x1FFF. Some of them are mandatory and others are optional. The following table lists the available objects, and the ones that are currently implemented in this stack.

Index Name Implemented
1000 device type yes
1001 error register yes
1003 manufacturer status register yes
1005 COB-ID SYNC yes
1006 communication cycle period yes
1007 synchronous window length yes
1008 manufacturer device name yes
1009 manufacturer hardware version yes
100A manufacturer software version yes
100C gard time no
100D life time factor no
1010 store parameters no
1011 restore default parameters no
1012 COB-ID TIME yes
1013 high resolution time stamp yes
1014 COB-ID EMCY yes
1015 Inhibit Time EMCY yes
1016 Consumer heartbeat time yes
1017 Producer heartbeat time yes
1018 Identity Object yes
1021 Store EDS yes
1022 Storage Format yes

Check configuration on how to access these entries.

These entries are different than regular OD entries as they use special extensions that can perform various operations on the running CANopen node. You can define your own CANopen extensions for this, you need to create two functions :

  • An od.StreamReader that will be called on entry read access
  • An od.StreamWriter that will be called on entry write access

The default implementations, i.e. for regular reading and writing are od.ReadEntryDefault and od.WriteEntryDefault.

odict := od.Parse("../testdata/base.eds", 0x20)
entry := odict.AddVariableType(index, indexName, od.DOMAIN, od.AttributeSdoRw, "")
entry.AddExtension(someObject,od.ReadEntryDefault,od.WriteEntryDefault)

Some pre-made extensions are available : 

odict := od.Parse("../testdata/base.eds", 0x20)
// this will create a file on disk that will be accessible by SDO block transfer
entry := odict.AddFile(0x3333, "File entry", "./path_to_file.txt", os.O_RDWR|os.O_CREATE, os.O_RDWR|os.O_CREATE)