iecstruct

A NodeJS library for parsing and saving IEC 61131-3 structs and types from/to binary buffers.

Support for types

All variable types are supported, look in table below for syntax.

Variable type	ST Syntax	iecstruct syntax
ARRAY	ARRAY[1..25] OF VARIABLETYPE	new iecstruct.ARRAY(VARIABLETYPE, 25)
STRUCT	TYPE name : STRUCT .. END STRUCT	new iecstruct.STRUCT()
STRING	STRING[20]	new iecstruct.STRING(20)
WSTRING	WSTRING[20]	new iecstruct.WSTRING(20)
ENUM	see note 1	see note 1
BOOL	BOOL	iecstruct.BOOL
BYTE	BYTE	iecstruct.BYTE
WORD	WORD	iecstruct.WORD
DWORD	DWORD	iecstruct.DWORD
SINT	SINT	iecstruct.SINT
USINT	USINT	iecstruct.USINT
INT	INT	iecstruct.INT
UINT	UINT	iecstruct.UINT
DINT	DINT	iecstruct.DINT
UDINT	UDINT	iecstruct.UDINT
LINT	LINT	iecstruct.LINT
ULINT	ULINT	iecstruct.ULINT
REAL	REAL	iecstruct.REAL
LREAL	LREAL	iecstruct.LREAL
TIME	TIME	iecstruct.TIME
TIME_OF_DAY (TOD)	TOD	iecstruct.TOD
DATE	DATE	iecstruct.DATE
DATE_AND_TIME (DT)	DT	iecstruct.DT

All variable types, also included the types you "create" by making structs or arrays, have the same two methods, and a parameter:

• asObject([buffer],[offset])
• fromObject(object, [buffer], [offset])
• bytelength

asObject[buffer],[offset])

Returns a javascript object containting a javascript version of the data contained in buffer.

fromObject(object, [buffer], [offset])

Writes the object back to the buffer, according to the variable type you are using. Se examples below.

bytelength

Holds the number of actual bytes the specified variable/struct would need to read/write to a buffer.

Note 1: Heres an example of a ENUM in structured text, and then with iecstruct:

TYPE E_TRAFFIC_SIGNAL:
    (
        Red,
        Yellow:=10,
        Green
    );
END_TYPE

var E_TRAFFIC_SIGNAL = new iecstruct.ENUM({
    Red: '',
    Yellow: 10,
    Green: ''
});
 
/* OR */
 
var E_TRAFFIC_SIGNAL = new iecstruct.ENUM()
    .addValue('Red')
    .addValue('Yellow', 10)
    .addValue('Green');
 

Enum variables will return string names for the known enum values, and plain digits if an invalid ENUM value is set/read.

Examples

Struct with structs and arrrays

var iecstruct = require('iecstruct');
 
var E_TriggerFunction = new iecstruct.ENUM({
    TRG_RE: '',
    TRG_FE: '',
    TRG_HOLD: ''
});
 
 
var ST_ScenarioTrigger = new iecstruct.STRUCT()
    .addElement('eTriggerFunction', E_TriggerFunction)
    .addElement('nElementNo', iecstruct.UINT);
 
var ST_Scenario = new iecstruct.STRUCT()
    .addElement('sName', new iecstruct.STRING(256))
    .addElement('bScenarioEnabled', iecstruct.BOOL)
    .addElement('bScenarioInUse', iecstruct.BOOL)
    .addArray  ('Triggers', ST_ScenarioTrigger, 100);
 
var Scenarios = new iecstruct.ARRAY('ST_Scenario', 100);
 
var obj = Scenarios.asObject();
obj[0].sName = "First scenario";
 
console.log(obj);
 
// Back to buffer:
Scenarios.fromObject(obj);
 
/* Buffer can be specified: */
var buffer = new Buffer(Scenarios.bytelength);
/* .. put code to insert data into buffer here */
var obj = Scenarios.asObject(buffer);
/* You can also write to a buffer */
Scenarios.fromObject(obj, buffer);
 
 

Reading/Writing arrays directly

var iecstruct = require('iecstruct');
 
/* MyArray : ARRAY[1..10] OF BOOL; */
var MyArray = new iecstruct.ARRAY(iecstruct.BOOL, 10);
var obj = MyArray.asObject(my_iec_buffer);
 
/* StructArray : ARRAY[1..25] OF ST_Simple; */
var ST_Simple = new iecstruct.STRUCT()
    .addElement('bActive', iecstruct.BOOL)
    .addElement('nNumber', iecstruct.UINT);
var StructArray = new iecstruct.ARRAY(ST_Simple, 25);
var obj = StructArray.asObject(my_iec_buffer);

Dual syntax for arrays

 
var ST_Scenario = new iecstruct.STRUCT()
    .addElement('sName', new iecstruct.STRING(256))
    .addElement('bScenarioEnabled', iecstruct.BOOL)
    .addElement('bScenarioInUse', iecstruct.BOOL)
    .addArray  ('Triggers', ST_ScenarioTrigger, 100);
 
/* Is the same as */
 
var ST_Scenario = new iecstruct.STRUCT()
    .addElement('sName', new iecstruct.STRING(256))
    .addElement('bScenarioEnabled', iecstruct.BOOL)
    .addElement('bScenarioInUse', iecstruct.BOOL)
    .addElement('Triggers', new iecstruct.ARRAY(ST_ScenarioTrigger, 100));
 

License (MIT)

Copyright (c) 2014 Håkon Nessjøen [e-mail]

Permission is hereby granted, free of charge, to any person obtaining a copy of this software and associated documentation files (the "Software"), to deal in the Software without restriction, including without limitation the rights to use, copy, modify, merge, publish, distribute, sublicense, and/or sell copies of the Software, and to permit persons to whom the Software is furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY, FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM, OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE SOFTWARE.