• Azure Subscription
• Python 2.7
• Install python packages:

pip install retrying iotc pymodbus

1. Create an IoT Central application -Visit AzureIoTCentral and create a New Application.
   • Under Choose a payment plan select Pay-As-You-Go.
   • Under Select an application template select Sample Devkits.
   • Configure your application name, URL, and billing information (First 5 devices are free).
2. Create the template for your Modbus Gateway device
   • From the nav bar on the left, select Device Templates, click the + on the upper right corner, and select Custom.
   • Name your template.
   • Go to the Settings tab on the template and create a new Text setting with the following parameters:
   • From the Device Explorer, select the template you have just created and note the Template Id:

1. Configure config.py
   • From the Administration pane on the IoT Central app, select Device connection and note the Scope ID and Primary Key for the app.
   • Clone this repo onto your master device and open config.py.
   • Under IoT Central parameters, replace the placeholder values with the values noted from earlier.
2. Run the sample
   • From your terminal, navigate to the root directory of the repo and run:

   python main.py

   • The following output should appear:

   2019-05-07 14:18:55,713:[device.start()]: Starting loop for device modbusmastertests
   2019-05-07 14:19:09,556:[device._on_connect()]: Connected/Disconnected modbusmastertests successfully
   2019-05-07 14:19:09,558:[device._on_message_sent()]: Sent message for modbusmastertests successfully
   2019-05-07 14:19:09,588:[device.start()]: Started loop for device modbusmastertests
   2019-05-07 14:19:09,809:[device._on_settings_updated()]: Settings updated for modbusmastertests. slavesconfig: {u'$version': 1, u'value': u' '}
   2019-05-07 14:19:09,825:[master_device._process_setting()]: Received config file:
   
   2019-05-07 14:19:09,826:[master_device._process_setting()]: ValueError or KeyError has occured while parsing JSON: No JSON object could be decoded
   2019-05-07 14:19:09,828:[device._on_settings_updated()]: Settings updated for modbusmastertests. echo: {u'$version': 1, u'value': 0}
   

   • From the Device Exporer pane, navigate to your template. There should now be a new device modbusmastertest. Select the device, then copy the contents of sampleconfig.txt into the text setting for Slaves Config and click Update:

   • After a few moments, a new Real device will appear under the MX Chip template with simulated Temperature and Humidity data. You may also set the Voltage setting, and your master device will print that it is simulating a voltage write.

Currently, this code only supports homogenous slave devices. The config file pushed down to the master device follows this structure:

{
    "modelId": "slavemodelID", 
    "updateInterval": 1,
    "activeRegisters":
    [
        {
            "registerName": "sensor1",
            "address": 0,
            "type": "ir"
        },
        {
            "registerName": "sensor2",
            "address": 1,
            "type": "ir"
        },
        {
            "registerName": "setting1",
            "address": 0,
            "type": "hr"
        },
        {
            "registerName": "coil1",
            "address": 0,
            "type": "co"
        },
        {
            "registerName": "discreteinput1",
            "address": 0,
            "type": "di"
        }
    ],
    "slaves": 
    [
        {
            "deviceId": "slave2",
            "slaveId": 0
        },
        {
            "deviceId": "slave1",
            "slaveId": 1
        }
    ]
}

• modelId: This is the template Id for your slave devices
• updateInterval: The period for sending data to IoT Central, in seconds
• activeRegisters: List of active Modbus registers for the slave devices
  • registerName: The name of the register, which corresponds to the field name for the measurement/setting on IoT Central
  • address: Modbus address for the register
  • type: Register type - if not specified on your device, it is most likely a holding register. Type abbreviations are as follow:
    • Holding register: hr
    • Input register: ir
    • Coil: co
    • Discrete Input: di
• slaves: List of slaves controlled by the master device
  • deviceId: Device Id, corresponds to the Device Id that will display on IoT Central
  • slaveId: Modbus Slave Id - for serial Modbus devices, this will be an integer, while for TCP/IP devices this will be an IP address as a string

1. Physically connect your Modbus slave devices to the master device.
2. Create a template for your slave devices on the IoT Central app with the appropriate measurements and settings.
3. Configure the Modbus parameters section in config.py and restart the program.
4. Create a config file using the structure specified above and push it down to the master device from the Slaves Config setting.