This article will guide you through how to publish and subscribe data between various PLCs, sensors and protocols and to AWS IoT Core. You will find a video that shows all the steps and procedure as well as written details describing the steps on how to install AWS IoT Core certificate, adding the endpoint and topics, how you are tailoring and customizing the published payload from the PLCs and respective protocols.

To connect data from PLCs to AWS IoT Core, the MQTT connector is required to be installed on SIA Connect as IoT Core is based on MQTT. If it is not already installed, you can follow this link for a guide on how to do so. 

For a complete list of all supported devices and protocols check Supported Industrial & Buildings devices‍ article. 

This guide will take you through the following steps:

• Installing the Thing SSL certificate from IoT Core on SIA Connect
• Creating the Thing as Instance
• Adding topics for subscribing and publishing to the Thing

Video tutorial

This video shows how to connect PLCs to AWS IoT Core. For further details read the remanding guide.

 

Applying the AWS Things SSL certificates

In the previous step where a Thing was created in IoT Core, you were presented to the SSL certificates for the Thing.
These are the certificates used by SIA Connect to establish a secure & trusted connection to the Thing in AWS IoT Core.

You will need a private key, public key and Root CA certificate for the IoT Core as listed below (naming most likely differ):

The certificates need to be uploaded to SIA Connect in the MQTT connector in order for the connector to work properly.

• Go to  Connectors
• Locate the MQTT Connector and press Upload new file
• A popup will open where you can upload a file.
• Do this procedure for Root CA certificate, Private key and Device certificate

After this is done the Connector files will look something like the following:

When the certificates are uploaded they can then be used when creating a new instance for the Thing in AWS IoT Core.

Adding the Thing's endpoint as Instance

In order to add a connection from SIA Connect to the Thing in AWS IoT Core you will need to add a Instance pointing to the Thing's endpoint. To add a instance refer you can follow this guide showing how to add a instance‍.

The table below shows how to fill out the fields on the instance

When the IoT Core endpoint is added as a Instance the next step is to define and add all the MQTT topics you want to publish and subscribe to the IoT Core. This is done by adding a item defining this topic and is described in the next section.

Configuring topics as Items

When the instance has been set up with the proper endpoint, we next need to set up items that defines the topics to use when publishing and subscribing to the Thing in AWS IoT Core. To learn how to add an item you can follow this guide.‍

We will set up three items in this example. You can add and name the topics just as you desire:

The following image shows a item configuration for the PublishTopic item. The name of the item can be anything.

Defining message formats for the topics

In order to define and customize the payloads that are being published the Input template for the topics item can be set.
Below are some examples of how these payload and message formats can be set:

{
   "device": "%INSTANCE_MASTER.NAME%", 
   "item": "%ITEM_MASTER.NAME%", 
   "value": "%VALUE%", "time": "%VALUE.TIME%" 
}

{
   "device": "PLC Bottle Line", "item": "Bottle Counter", "value": "458",
   "time": "2022-02-03T07:47:26"
}

{ 
   "value": "%VALUE%", 
   "time": "%VALUE.TIME.FORMAT("h:m:s yy/d/M")%",
   "prod_id": "%UID_OF_PRODUCTION_ITEM%"
}

{ 
   "value": "458", 
   "time": "7:3:5 22/2/3",
   "prod_id": "ORDER XYZ12345" 
}

For a full reference of the available variables and parameters please refer to System variables‍, Instance variables‍ and Item variables‍.

That's it, now we are ready to create the mappings between the PLC data and the topics we just added.

Mapping data from the PLCs to AWS IoT Core

SIA Connect is able to read data from almost any PLC. This is done by creating an instance and setting the PLC up withing that instance. If you need help in doing so, our help-page contains various guides for creating instances for the specific PLC you want to use

For a PLC to transfer data to the AWS IoT core, you must use Mappings. Mappings is a SIA Connect feature where you can transfer data from one Instance to another. In this case, we have two instances, a PLC and the AWS IoT Core.

As Master item select the instance and item which masters when to transmit data. In this example we select Siemens S7 PLC and its item named Analog. As Slave item select the AWS instance and the desired Item which in this case is the topic. In this example it is instance named AWS and item named Publish.

In this window we can see how the mapping interface looks like

Data from the Siemens S7 PLC from the Analog item is now being published to the AWS IoT Core's topic named Publish. Continue this step with all the data items which you desire to publish to AWS IoT Core.

Following the next guide - Validating data exchange between AWS IoT Core and PLC - you can see the data being transferred between the AWS IoT Core and SIA Connect and verify that everything is working