Connecting to AWS IoT Core via MQTT

Overview

Let's connect a PLC via MQTT to IoT Core on Amazon Web Services (AWS Cloud) and exchange messages
Once data can be sent to IoT Core, it can be handled by AWS services (Lambda, DynamoDB, etc.)
As an example, how to insert data from a PLC into DynamoDB is covered on a separate page

Configuration

Preparation

Preparation on the AWS side

Create an AWS account and download the client certificate and private key in IoT Core
For the steps, see Preparing for MQTT connection to AWS IoT Core in the how-to navigator

Downloading the PLC library

Download it here
OMRON official MQTT communication library download page

PLC network settings

Set the PLC network settings in Sysmac Studio as follows

Secure socket settings for the PLC CPU unit

The basic flow is

1. Put the PLC in Program mode
2. Run the "Secure Socket Setting Command" shortcut in the folder C:\ProgramData\Omron\Sysmac Studio\StartMenu\Sysmac Studio\Tools
   (or C:\ProgramData(x86)\Omron\Sysmac Studio\StartMenu\Sysmac Studio\Tools)
3. Transfer the certificate and key files to the PLC
   C:\ProgramData\Omron\Sysmac Studio\StartMenu\Sysmac Studio\Tools\TLSSettingTool>tlsconfig setSessionInfo /id 0 /key "C:\private\xxx-private.pem.key" /cert "C:\certs\xxx-certificate.pem.crt" /ip:192.168.10.201 /f
   (Match the xxx part of xxx-private.pem.key and xxx-certificate.pem.crt to the names of the downloaded files. You may rename them if the names are long)
   

NOTE
If typing in the command prompt is tedious, drag a file from Explorer into the command prompt where the file name goes, and the file name is entered

For detailed steps, see "A-3-6 Secure Socket Settings for the CPU Unit" in the MQTT library manual
The library manual is created under the folder C:\OMRON\Data\Lib\MQTT_Comm after setup

PLC settings

Adding the MQTT library

Select [Project] - [Library] - [Library Reference] from the Sysmac Studio menu and add the downloaded MQTT library in the Library Reference dialog

Creating the program

Connecting to AWS IoT Core

Establish a connection with AWS using the MQTT client (MQTTClient)
Turn trigger1 ON; when Connected turns ON, it is connected
While connected, messages can be exchanged

For ConnectionSettings.IpAdr, enter the endpoint from the AWS IoT Core settings screen

Sending a message from the PLC

Send a message with the publish instruction (MQTTPubString)

Check the received data with the AWS MQTT test client

In the "Subscribe to a topic" tab, enter "test/#" in the topic filter and click [Subscribe]; "test/#" is added to the subscriptions below
It is now waiting to receive

NOTE
# is a wildcard
A message is shown when a topic whose name starts with "test/" is received

On the PLC, turn trigger2 ON to send a message ({"message":"Hello!"})

When received on the AWS side, the received message is shown

Receiving a message on the PLC

Receive messages with the subscribe instruction (MQTTSubString)

On the PLC, turn trigger3 ON to wait for messages

The MQTTSubString instruction has an Enable input, so it waits to receive while trigger3 is ON

Send a message from the AWS MQTT test client

In the "Publish to a topic" tab, enter "test/message1" as the topic name, enter the message in the message payload and click [Publish]
The sent message is shown in the subscriptions

When the PLC receives a message, the received message goes into the output variable

Download

sampleIIot_AWS.zip

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