How to Connect Your Embedded System to AWS IoT Core with MQTT

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In this tutorial, we are going to show you exactly how to get started with the AWS IoT Core service by using it to connect to an IoT embedded system. Specifically, we are going to connect to our newest product, the ARM®-Powered MODM7AE70 system on module development kit using the MQTT protocol. This will be implemented using NetBurner’s core libraries, a small (and slightly modified) subset of the AWS C-based SDK, NBEclipse (our Eclipse based IDE), and of course, the AWS IoT Core service itself. The project, which includes all of the files needed to get started, can be found in our AWS IoT Core MQTT repo here (more on this in a bit).

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Read more about the IoT Core Cloud Service here.

IoT Dev Kit Featured in this Article

Netburner ARM Cortex M7 embedded Development Kit for IoT product development and industrial automation.

Or, learn more about NetBurner IoT.

To avoid getting lost in the weeds and to keep any possible confusion at bay, We are going to keep the application in this example extremely simple. The MODM7AE70 will listen for incoming messages and periodically send them out using the ever popular MQTT protocol. These messages will be viewable from a serial terminal connected to the device as they are received and sent. Additionally, the last message sent and received will be viewable through a webpage that is hosted directly from the NetBurner device. All of our network enabled devices can act as a web server over both HTTP and HTTPS with minimal effort. The functionality of our application will be tested by using an MQTT client that is available through the AWS IoT Core service console.

The rest of this article will be split into three bite-sized chunks. First, we will set up the AWS IoT Core service and use it to register your device. Next, we will look at the changes that need to be made to the application in order to get it to play nicely with the AWS IoT Core service, as well as how to build the project and load it onto your device. Finally, we will show you how to test that the connection is successful and let you bask in the glory of all your… glory.

Let’s get to it.

Prerequisites and Assumptions

As a prerequisite, we should mention that this project was built for NetBurner 3.x, which is the latest version of our tools and libraries. This supports NetBurner’s MOD54415, the MOD54417, the NANO54415, the SB800EX, and the aforementioned MODM7AE70. Porting this project back to earlier versions of our tools is certainly possible, but it won’t be quite as straightforward as we have laid out here.

We will assume that before beginning, you have the latest version of our tools (NNDK 3.x) downloaded and installed, and that your is module up and connected to your network. We are also going to assume that you have downloaded or cloned the source code from the repo, here.

If you’re unfamiliar with using GitHub, you can either download the repository in a .zip file, or clone it using the steps listed here. Regardless of whether you clone it or extract the contents of the .zip file to your computer, you should end up with a folder containing two subfolders named src and html. These folders contain the code for the application. The folder containing them will be the root folder for our application. For us, this folder will be \AwsIotCoreMqttBase, and it will be used as a point of reference throughout the remainder of the tutorial.

Finally, we recommend having a way to view the serial data coming directly from your module via the development board. There are two easy ways to do this. First, if you have the USB to micro-USB cable that came with your development kit, you can set the jumper configuration on your development board so that it both sends serial output to and receives power from the micro-USB jack. Alternatively, you can set the jumpers on the development board to use the DB9 port (UART0) for serial output. Please see the “Quick Start Guide” that came with your development board for further information on how to configure the jumpers on your board.

If you don’t happen to have a serial port on your computer (many don’t these days) and are missing your USB to micro-USB cable, you can use a USB to serial adapter to get the job done. This of course assumes you have a USB port.

Setting Up AWS IoT Core

Before setting up an AWS IoT “thing”, as they are affectionately termed, you will need to create an AWS management console account. The account itself is free (though service pricing varies, check out this link for specifics regarding IoT Core), and will open the gateway for a ton of different AWS cloud services. If you haven’t done this already, you can take care of that here. Go ahead, we’ll wait.

Now that you have officially joined the club, go ahead and log into your account if you haven’t already. As a side note, we are going to use our root account to avoid running into permissions issues during the course of the tutorial. If you want to do this the way AWS recommends, you will have to create a secondary user account that you will then need to give the required IoT Core permissions to through IAM. After you log in, you should be greeted with the “AWS Management Console” page, shown in Figure 1.

AWS Management Console

 

Figure 1: AWS Management Console

From here you will want to navigate to the IoT Core service. You can do that by using the “Find Services” search field on the page, as we have done above, or clicking on the “Services” dropdown menu found in the top banner of the page.

Figure 2: IoT Landing Screen

 

Figure 2: IoT Landing Screen

From here, you will hit the AWS IoT landing screen, as shown in Figure 2, above. There’s some great info here, and we encourage everyone to take a look around when they can. We’re on a mission, though, so we’re going to bypass this and get straight to adding a device. Click on the “Get Started” button, and you should see a welcome screen as shown below in Figure 3.

Figure 3: IoT Core Welcome Screen

 

Figure 3: IoT Core Welcome Screen

Before we can register our device as a “thing”, we need to setup a “policy” for it. This policy will be assigned to our “thing” during the registration process, and will grant it the permissions needed to access the MQTT topics that we will use to send and receive messages. From the left hand menu, select “Secure”, and then the submenu of “Policies”, as shown below in Figure 4. This should take you to the console displayed, which notifies us that we don’t currently have any policies.

Figure 4: Creating a Policy

 

Figure 4: Creating a Policy

Click on the button labeled, “Create a policy”, which will take you to the screen shown below in Figure 5. 

Figure 5: Initial Policy Creation Screen

 

Figure 5: Initial Policy Creation Screen

From the policy creation page, we will add the statements that will dictate what our connected devices are allowed to do. We assign our policy the name “NBTutorial”, and add four statements with the information listed below. Notice that when you type in the action, the field labeled “Resource ARN” will be automatically populated. Check “Allow” under the “Effect” field, and replace the last portion of each Resource ARN that reads, “replaceWithA”, with an asterisk (*). When finished, you should have the following statements:

ActionResource ARN
iot:Connectarn:aws:iot:&ltyour region&gt:&ltyour account #&gt:client/*
iot:Publisharn:aws:iot:&ltyour region&gt:&ltyour account #&gt:topic/*
iot:Receivearn:aws:iot:&ltyour region&gt:&ltyour account #&gt:topic/*
iot:Subscribearn:aws:iot:&ltyour region&gt:&ltyour account #&gt:topicfilter/*

Table above provides some guidance on how to configure the AWS IoT Core policies to work for you.

 Figure 6: Finished AWS IoT Core Policy

 

Figure 6: Finished AWS IoT Core Policy

Please note that in a production environment, you will want to be a lot more selective with your policy creation (e.g., don’t use an asterisk at the end of a Resource ARN). We are keeping it very straightforward here to get the ball rolling, but we by no means endorse these sorts of cavalier policy settings in a live production environment.

When they have been entered, click “Create”. Now it’s time to register our “thing”.

Figure 7: Register a Thing on AWS IoT Core

 

Figure 7: Register a Thing on AWS IoT Core

Back at the main menu on the left pane, click on the “Manage” menu option, and then the “Things” submenu. Amazon kindly reminds us that we don’t actually have any “things” yet, so let’s take care of that now by clicking on the button labeled, “Register a thing”, as we see in Figure 7, above.

This will take us to a window that allows us to register a single “thing”, or multiple “things”. For this tutorial, we are going to stick to one, so go ahead and click on the button labeled, “Create a single thing”. This should bring us to the screen shown in Figure 8, where we will get to provide the details of our device.

 Figure 8: Add Your IoT Device

 

Figure 8: Add Your IoT Device

The only thing we are going to add here is the “Name”, which we will set to “NBTutorial”. Hit “Next”, and you will be taken to a screen where you can select how to associate your “thing” with the certificates that will be used to authenticate it with the AWS IoT Core service. We are going to let Amazon do the dirty work for us here, so go ahead and click the button at the top labeled, “Create certificate”. 

As of this writing, using their certificate creation process is recommended way to go and after running through all of the steps in this tutorial, we could see why. When the certificate has been generated, you will be taken to a screen similar to that shown in Figure 9, below. 

Short Aside: After hitting “Next”, you might instead get the following message: “We are provisioning a Device Gateway endpoint for your account. It may take a few minutes for the endpoint to be ready, after which you can connect devices to AWS IoT, publish/subscribe to topics, and access device shadows.” In this case, navigate back to the dashboard and click “Manage”, followed by the submenu item “Things” in the left pane. You should see your registered “NBTutorial” thing waiting for you there. Click on it, followed by the “Security” menu item that will be listed on the left side of the screen. Finally, click the button labeled “Create Certificate” to move on.

Figure 9: Certificate Created!

 

Figure 9: Certificate Created!

We need to do a few things here before we can proceed. First, we will want to download the certificate and the private key. We actually recommend downloading all three (the certificate file and the public and private key files) and tucking them away someplace safe, but you only need the certificate and the private key to have your device connect using our application. For now, we are going to put them in the root directory of the project, \AwsIotCoreMqttBase. After you have these moved appropriately, click the button labeled, “Activate”.

Last but not least, we are going to attach the policy that we created earlier to our device. Click the button labeled, “Attach a policy”. This will advance you to a screen that will let you attach any of the policies you have created previously to the certificate, as we see in Figure 10 below. 

Figure 10: Attach A Policy

 

Figure 10: Attach A Policy

Because we’ve only created the one, that’s all we should see. Click on the checkbox next to it in order to select it, and then hit the final button, “Register Thing” or “Done” (depending on if you were able to complete the registration all the way through in one go or not).

Success! If all went according to plan, you should be taken back to a list of your currently active “things”, which includes the one we just created, as shown in Figure 11.

 Successfully added a Thing with AWS IoT Core

 

Figure 11: Huzzah! Successfully added a Thing with AWS IoT Core

Modifying, Building, and Loading the Application

At this point we are going to step away from AWS, and focus on getting the application up and running on your device. 

Compile the Certificate and Private Key

Remember the certificate and private key we created previously? It’s time to whip those bad boys out, because we are going to compile them directly into our application. Before we can do that, we need to turn them into something the device can actually understand.

On a command-line terminal, navigate to the folder where you tucked those files away (\AwsIotCoreMqttBase for us) and run the command:

compfile privatekey PRIVATE_KEY_LEN privatekey.cpp

Substitute with the name of the private key file you downloaded previously. This file usually has the format -private.pem.key. If you run into problems running compfile, make sure that the directory where all of NetBurner’s tools are installed is on your path. This is typically \nburn\pcbin.

Running the command above creates the file privatekey.cpp, which contains the entire contents of the private key stored in the form of an array. The length of this array is also stored in the file as the constant, PRIVATE_KEY_LEN.

Next, do the same for the certificate with the following command:

compfile certificate CERTIFICATE_LEN certificate.cpp

Substitute with the file you downloaded in the previous section that contains the certificate. This file usually has the format -certificate.pem.crt. Similar to the command above, it generates the file certificate.cpp, which defines an array that holds the certificate data as well as the length of that array, which is stored in the variable CERTIFICATE_LEN.

If this all worked out, you will now see the two new C++ source files, privatekey.cpp and certificate.cpp, in our root directory, \AwsIotCoreMqttBase, each with a size greater than 0. If not, you may need to repeat the above steps and do a bit of troubleshooting.

At this point, let’s go ahead and move the new files to our \AwsIotCoreMqttBase\src directory, which will save us a step down the road with our NBEclipse project. Speaking of which, let’s go ahead and move on to that now.

Make a Project in NBEclipse

NBEclipse is NetBurner’s Eclipse based IDE that provides everything needed to develop, build, and deploy an application to your NetBurner device. It can be found in the NNDK install directory (nburn by default) under the subfolder, NBEclipse. Go ahead and launch that application now, and feel free to accept the default directory for your workspace when the dialogue shows up.

Detailed information on creating a project and developing your application in NBEclipse can be found in our documentation, here. We will go ahead and give a brief overview, however, to get you started as quickly as possible.

We are going to use the Project Wizard to get us started and will create our project so that it actually points to our root folder, \AwsIotCoreMqttBase, which will prevent us from having to import any code. To do this, navigate to File->New->Project from the toolbar at the top of the window, as shown in Figure 12.

Figure 12: Create a New Project in NBEclipse IDE

 

Figure 12: Create a New Project in NBEclipse IDE

This should open up the New Project Wizard, as shown in Figure 13.

Figure 13: The New Project Wizard

 

Figure 13: The New Project Wizard

Make sure that “NetBurner Project” is selected under the “NetBurner” option, and hit “Next”. This should bring you to the window shown below in Figure 14.

Figure 14: Naming Your Project

 

Figure 14: Naming Your Project

Typically, the only thing we do here is give the project a name and move on. However, in this instance we are also going to uncheck the box labeled, “Use default location”, and hit the  “Browse” button to navigate to the folder where you have cloned the repo. For us, this was \AwsIotCoreMqttBase. Make sure that in the window labeled “Toolchains”, the “NetBurner Toolchain” is listed and selected.

Hitting “Next” from this window will take us to where we can select which configurations we would like to build. We want to be able to run the application in both “Debug” and “Release” mode, so leave the options checked, and hit “Next” again.

On the next window, shown in Figure 15, we are able to specify which platform we would like to build this application for. We are going to select the MODM7AE70. If you are using one of our other platforms select it accordingly. If your device is already plugged in and connected to your network, you can go ahead and find it’s IP address by hitting the button labeled, “Search”, and then selecting it from the list that pops up on your screen.

Figure 15: Selecting Your Device

 

Figure 15: Selecting Your Device

If your device isn’t connected, you can pass on this field for now, and just hit the “Next” button. The next window shows some basic components that can be automatically added to the application, but since we are using the code from the folder in the repo, we can skip all of these and just hit “Finish”.

With this complete, you should see your project created and listed in the “Project Explorer” tab on the left side of NBEclipse. You might notice that your project automatically starts to build from the console output in the bottom right. If we did everything correctly with our project setup and remembered to move certificate.cpp and privatekey.cpp to \AwsIotCoreMqttBase\src, then it should build successfully. You will know you’re ready to rock if you see the following at the bottom of your NBEclipse console window:

 Figure 16: Another Milestone Reached

 

Figure 16: Another Milestone Reached

If, instead, you see an error, ensure that the src folder listed in your project is mapped properly to \AwsIotCoreMqttBase\src by verifying that all of the source files show up in your “Project Explorer” tab under the src folder. Also double check that both the certificate and private key file generated in the earlier section are listed as well.

Make a Few Changes

To get our device to successfully connect to the AWS IoT Core service, we will need to make a few changes to the aws_iot_config.h file in our source code. Open this file from your project’s src folder in NBEclipse. At the top of this file, two macros are defined which will need to be modified. These are AWS_IOT_MQTT_HOST and AWS_IOT_MQTT_CLIENT_ID.

AWS_IOT_MQTT_HOST: This is the endpoint that we will need to connect to and authenticate with. To find this value, go to your AWS IoT Core management console, click “Manage” followed by the submenu item, “Things”, in the left pane, and then click on your “NBTutorial” registered “thing”. On the left side of the main window, you will find a list of menu options. Of these, click on “Interact”, which should bring you to a page that looks similar to the one in Figure 17.

 Figure 17: AWS IoT Core “Thing” Details

 

Figure 17: “Thing” Details

The value that we are looking for is the obnoxiously long one listed under the “HTTPS” heading. Copy and paste that value in place of the text, , in your aws_iot_config.h file.

AWS_IOT_MQTT_CLIENT_ID: This is a unique client ID for your device and should be unique for each device connecting to this endpoint. We chose to be boring and used our MAC address, but you can feel free to come up with something as creative and interesting as you like (as long as it’s unique). If you’d like to use your MAC address as well, you can find it at the bottom of the barcode sticker on your module, or by visiting https://discover.netburner.com. Whatever you choose, copy that value over the text, , in your aws_iot_config.h file.

When you save your NBEclipse project, it should again automatically build the project and show a “Build Finished” message as mentioned earlier. If not, you can manually trigger the build by choosing Project->Build Project from the NBEclipse menu.

Load Your Application

At this point, we are ready to load our application on the device. You should be able to automatically set up a run configuration from the top menu of the IDE by selecting Run->Run As->As Neturner Application. Please see our documentation for more details on run configurations.

You can add your device’s IP address to the project if for some reason your device wasn’t associated with the project during the creation process. Do this by right clicking on the project in the “Project Explorer” tab, and selecting the “Properties” option at the very bottom of the list. From there, select “NetBurner Options” from the list on the left hand side of the window that shows up, and then type in your devices IP address in the appropriate field under the “Device Options” section, as shown in Figure 18 below. Again, you can find your device IP via: https://discover.netburner.com/.

Figure 18: Assigning an IP address to your project

 

Figure 18: Assigning an IP address to your project

Optional (and Recommended) Step: You can monitor the serial output of your application through a MTTTY terminal when the program has been successfully loaded. Do this by connecting your development board directly to your computer. Depending on your board’s jumper configuration, this will be done through the UART0 DB9 port or through the micro USB jack, as explained in the “Prerequisites and Assumptions” section above. If all goes well, after some initial initialization and connection information, you should see the “Publish Success” messages periodically scroll by, as is shown in Figure 19 below:

Figure 19: Successful Messages Published

 

Figure 19: Successful Messages Published

Testing

Now comes the moment you’ve been waiting for. It’s time to send and receive messages to the AWS IoT Core service using the MQTT protocol with your NetBurner module. For this next set of steps, we are going to need to head back over to the AWS IoT Core management console. This time, however, we are going to select “Test” from the left hand menu, which should take you to a console similar to that shown in Figure 20.

 

Figure 20: MQTT Test

In our self proclaimed genius, we have cleverly named the MQTT topic being used to post from the NetBurner module to AWS as, “NBTutorial/ToAws”. Go ahead and enter this (without the quotes) in the “Subscription topic” field, and hit the button labeled “Subscribe to topic”. 

If all goes well and your device is running, you should see MQTT messages start to show up in the bottom portion of the window, as we see in Figure 21. If not, go back and look at the “Optional (and Recommended) Step” above, and verify that your device is properly initializing the AWS SDK in the serial terminal. Also verify that port 8883 isn’t block on your firewall, as this is the default port for MQTT and restricting it will prevent your NetBurner device from being able to communicate with AWS. Finally, verify that the Resource ARNs in the policy we created above all properly end in the (*).

Figure 21: Testing NetBurner Device Publishes

 

Figure 21: Testing NetBurner Device Publishes

Next we want to see if our device has successfully subscribed to a channel. In the same AWS console click on the link, “Publish to a topic”, located on the secondary left menu under the heading, “Subscriptions”. The bottom portion of the console where we saw the NetBurner device’s messages coming in should be replaced by a small box titled, “Publish”. It should contain a text field for the topic, as well as a text field for the message to send, and finally a button labeled, “Publish to topic”. This can be seen below in Figure 22.

Figure 22: Testing Subscribe on the NetBurner Device

 

Figure 22: Testing Subscribe on the NetBurner Device

For this topic, enter, “NBTutorial/ToNb”. This is important as it is the topic that our application is looking to receive messages on. You can leave the message as the default value which is “Hello from AWS IoT console,” or you can modify to fit your fancy. Notice, though, that it follows a JSON format. 

Go ahead and hit that magic button on the side (“Publish to topic”) when these fields have been filled out. If you happen to be connected directly to your device through UART0, look for your message to show up in the serial terminal as we’ve outlined it below in Figure 23.

Figure 23: The Sweet Taste of Victory . Test it out with NetBurner's MTTTY serial utility.

 

Figure 23: The Sweet Taste of Victory . Test it out with NetBurner’s MTTTY serial utility.

You can also view the very last message that was sent and received on the device from a web browser if you’re not a fan of serial terminals or don’t have a serial to USB adapter. To do this, open your browser of choice and enter your device’s IP address in the URL bar at the top. Again you can the IP address using the URL, https://discover.netburner.com/. Putting this IP address in your browser will direct you to a simple webpage hosted from the NetBurner module that displays the most recent messages sent and received, as shown in Figure 24 below.

 Figure 24: Better Looking Victory . Test everything out with discover.netburner.com

 

Figure 24: Better Looking Victory . Test everything out with discover.netburner.com

With this last step complete, our tutorial comes to a close. That said, it’s only fair to point out that we have glossed over an awful lot to get to this point.  Next, read our code review article to understand the inner workings of this application.

Getting your devices connected to the AWS IoT Core service is really only the beginning. From here, you will be able to take advantage of the myriad of services that AWS provides. We will cover how to get started with some of these as well in future tutorials (not so subtle hint, our next one starts with “Elas”, and ends with “tic Beanstalk”).

If you have any questions about incorporating an embedded system into your cloud service, or would like more information about our platforms, please feel free to reach out to us at sales@netburner.com. Please comment if you run into any issues or have other questions.

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