ModbusRTU

DeviceJS driver/module for Modbus RTU devices

About Modbus

Modbus is a serial communication protocol developed by Modicon published by Modicon® in 1979 for use with its programmable logic controllers (PLCs). In simple terms, it is a method used for transmitting information over serial lines between electronic devices. The device requesting the information is called the Modbus Master and the devices supplying information are Modbus Slaves. In a standard Modbus network, there is one Master and up to 247 Slaves, each with a unique Slave Address from 1 to 247. The Master can also write information to the Slaves.

Prerequisite

Should have installed and running DeviceJS (comes with database, DeviceDB)

Install

cp devicejs.json package.json

npm install

Run

devicejs run ModbusRTU

Note: Might have to be super user to access terminals

Start Device Controllers

Initialized device meta data and start controller in 2 simple steps:

1. Create a JSON object with these properties

{
	"name": "imod6Switch1", //Make sure to change this for each resource so that their is no ambiguity. ResourceID is generated using this, if not specified.
	"resourceID": "", //Filename, Specify a unique ID used to register this resource with deviceJS, usage- dev$.selectByID(resourceID);
						// If not specified, will be generated by controller using name, slave address, interfaces, genre
	"deviceGenre": "switch", //thermometer, switch, lightDetector, register, coil
	"resourceType": "Core/Devices/ModbusRTU", //+ resourceID, Note- a resource type should have same interfaces
	"version": "0.0.1",
	"slaveAddress": 2, //Modbus slave address
	"enable": true, //If false will not be started
	"overwrite": true, //If true, it will overwrite the changes made to this device controller during runtime
	"generateControllerFiles": true, //If true will generate files on disk otherwise not
	"interfaces": {
		"Facades/Switchable": { //This should match the supported interfaces (described in core-interfaces)
			"dataAddress": 203, //Cannot be array of non consecutive addresses
			"range": 1, //If not specified, default- 1
			"pollingInterval": 1000, //Specify polling interval in ms, min 500ms
			"outgoingOperation": "{{value}} > 100 ? 'off' : 'on'", //If you want perform operation on output
			"eventThreshold": 10, //incase of an array, it will compare each element if any element is greater than this then an event is emitted
			"unit": "" //Default unitless
		}
	}
}

2a. Save the above object in a file and place it in the contorllers/resourceTypes directory. Example: switch1.json

dev$.selectByID('ModbusDriver').call('start', 'switch1.json')

Note: Make sure it is the same file system as on which you are running ModbusRTU module

2b. Save the object in a file and place it in any directory. Example: /home/foo/workspace/switch1.json, Specify absolute path

dev$.selectByID('ModbusDriver').call('start', '/home/foo/workspace/switch1.json')

Note: Make sure it is the same file system as on which you are running ModbusRTU module

2c. Open up devicejs shell and do the following

var fs = require('fs');
var jsonminify = require('jsonminify');
var dcMetaData = fs.readFileSync('/home/foo/workspace/switch1.json', 'utf8')
dev$.selectByID('ModbusDriver').call('start', JSON.parse(jsonminify(dcMetaData)));

2d. Login to cloud.wigwag.com and go to inspect element --> console and run

dev$.selectByID('ModbusDriver').call('start', {
	"name": "imod6Switch1", //Make sure to change this for each resource so that their is no ambiguity. ResourceID is generated using this, if not specified.
	"resourceID": "", //Filename, Specify a unique ID used to register this resource with deviceJS, usage- dev$.selectByID(resourceID);
						// If not specified, will be generated by controller using name, slave address, interfaces, genre
	"deviceGenre": "switch", //thermometer, switch, lightDetector, register, coil
	"resourceType": "Core/Devices/ModbusRTU", //+ resourceID, Note- a resource type should have same interfaces
	"version": "0.0.1",
	"slaveAddress": 2, //Modbus slave address
	"enable": true, //If false will not be started
	"overwrite": true, //If true, it will overwrite the changes made to this device controller during runtime
	"generateControllerFiles": true, //If true will generate files on disk otherwise not
	"interfaces": {
		"Facades/Switchable": { //This should match the supported interfaces (described in core-interfaces)
			"dataAddress": 203, //Cannot be array of non consecutive addresses
			"range": 1, //If not specified, default- 1
			"pollingInterval": 1000, //Specify polling interval in ms, min 500ms
			"outgoingOperation": "{{value}} > 100 ? 'off' : 'on'", //If you want perform operation on output
			"eventThreshold": 10, //incase of an array, it will compare each element if any element is greater than this then an event is emitted
			"unit": "" //Default unitless
		}
	}
});

References:

1. Facades - You can find the built-in facades with devicejs here https://github.com/WigWagCo/devicejs-core-modules/tree/development/core-interfaces/facades. To create your own facade follow how to start device controller documentation.

Troubleshooting:

Useful commands to get more info about the driver, registered resources, running device controllers etc. Execute the following commands on deviceJS shell.

1. List: Get all the resouceIDs registered by ModbusRTU driver

dev$.selectByID('ModbusDriver').call('listResources').then(function(resp) { if(resp.ModbusDriver && resp.ModbusDriver.response && resp.ModbusDriver.response.result) { console.log(resp.ModbusDriver.response.result) } else { console.log('Failed: ', resp.ModbusDriver.response.error) } }) 

2. Get Device Metadata/Definition: Get device definition/metadata for resourceID. Get one of the resourceID from the result of List command and replace it with the string 'resourceIDinsinglequotes'

dev$.selectByID('ModbusDriver').call('getMetadata', resouceIDinsinglequotes).then(function(resp) { if(resp.ModbusDriver && resp.ModbusDriver.response && resp.ModbusDriver.response.result) { console.log(resp.ModbusDriver.response.result) } else { console.log('Failed: ', resp.ModbusDriver.response.error) } }) 

3. State: Get the state of the device controllers

dev$.selectByID('ModbusDriver').call('listResourceStates').then(function(resp) { if(resp.ModbusDriver && resp.ModbusDriver.response && resp.ModbusDriver.response.result) { console.log(resp.ModbusDriver.response.result) } else { console.log('Failed: ', resp.ModbusDriver.response.error) } }) 

4. Stop: Stop running device controller. Note: If the modbus driver restarts then this device controller will be started. To prevent that or permanently disable or delete a device follow disable or delete command respectively.

dev$.selectByID('ModbusDriver').call('stop', resouceIDinsinglequotes).then(function(resp) { if(resp.ModbusDriver && resp.ModbusDriver.response && resp.ModbusDriver.response.result) { console.log(resp.ModbusDriver.response.result) } else { console.log('Failed: ', resp.ModbusDriver.response.error) } }) 

5. DeleteAll: Reset the modbus driver. This command will delete the running and stored device controllers and wipe the memory to start afresh.

dev$.selectByID('ModbusDriver').call('deleteAll').then(function(resp) { if(resp.ModbusDriver && resp.ModbusDriver.response && resp.ModbusDriver.response.result) { console.log(resp.ModbusDriver.response.result) } else { console.log('Failed: ', resp.ModbusDriver.response.error) } }) 

6. LogLevel: To reduce or increase the logging from Modbus driver. Available- error- 0, warn- 1, info- 2, debug- 3, trace- 4

dev$.selectByID('ModbusDriver').call('logLevel', 3).then(function(resp) { if(resp.ModbusDriver && resp.ModbusDriver.response && resp.ModbusDriver.response.result) { console.log(resp.ModbusDriver.response.result) } else { console.log('Failed: ', resp.ModbusDriver.response.error) } }) 

Terminology

1. Device Definition/Metadata- This is the JSON object which specifies the details to start device controller such as name, interfaces, slave address, polling interval etc.
2. Device controller- Controller which lets to control or get state information of a particular endpoint connected with Modbus.
3. ResourceID: Identifier with which device controller was started. It is a unique string used to registered a device controller with deviceJS. You will this as- dev$.selectByID('resourceID').get('power') or dev$.selectByID('resourceID').set('power')