Using the AWS IoT Device SDK for Embedded C - AWS IoT

Using the AWS IoT Device SDK for Embedded C

This section describes how to run the AWS IoT Device SDK for Embedded C.

Install the AWS IoT Device SDK for Embedded C

The AWS IoT Device SDK for Embedded C is generally targeted at resource constrained devices that require an optimized C language runtime. You can use the SDK on any operating system and host it on any processor type (for example, MCUs and MPUs). If you have more memory and processing resources available, we recommend that you use one of the higher order AWS IoT Device and Mobile SDKs (for example, C++, Java, JavaScript, and Python).

In general, the AWS IoT Device SDK for Embedded C is intended for systems that use MCUs or low-end MPUs that run embedded operating systems. For programming examples in the documentation, we use Raspberry Pi running embedded Linux.

Example

  1. Download the AWS IoT Device SDK for Embedded C to your Raspberry Pi from GitHub.

    git clone https://github.com/aws/aws-iot-device-sdk-embedded-c.git -b release

    This creates a directory named aws-iot-device-sdk-embedded-c in the current directory.

  2. Download mbed TLS to your Raspberry Pi from the mbed TLS website.

  3. Navigate into the /home/pi/Downloads directory. Expand the mbedtls-versionNumber-apache.tgz file for the latest version by using the following command.

    tar -xvf mbedtls-versionNumber-apache.tgz
  4. Copy the contents of mbedtls-versionNumber into the aws-iot-device-sdk-embedded-C/external_libs/mbedTLS directory using the following command.

    mv ~/Downloads/mbedtls-versionNumber/* ~/aws-iot-device-sdk-embedded-c/external_libs/mbedTLS

Sample app configuration

The AWS IoT Device SDK for Embedded C includes sample applications for you to try. For simplicity, this tutorial uses the subscribe_publish_sample application, which illustrates how to connect to the AWS IoT Core message broker and subscribe and publish to MQTT topics.

  1. Copy the certificate, private key, and root CA certificate you created in Create an AWS IoT thing for your Raspberry Pi into the aws-iot-device-sdk-embedded-C/certs directory.

    Note

    Device and root CA certificates are subject to expiration or revocation. If your certificates expire or are revoked, you must copy a new CA certificate or private key and device certificate onto your device.

  2. You must configure the sample with your personal AWS IoT Core endpoint, private key, certificate, and root CA certificate. Navigate to the aws-iot-device-sdk-embedded-c/samples/linux/subscribe_publish_sample directory.

    If you have the AWS CLI installed, you can use the aws iot describe-endpoint --endpoint-type iot:Data-ATS command to find your personal endpoint URL. If you don't have the AWS CLI installed, open your AWS IoT console. From the navigation pane, choose Manage, and then choose Things. Choose the IoT thing for your Raspberry Pi, and then choose Interact. Your endpoint is displayed in the HTTPS section of the thing details page.

  3. Open the aws_iot_config.h file and, in the Get from console section, update the values for the following:

    AWS_IOT_MQTT_HOST

    Your personal endpoint.

    AWS_IOT_MY_THING_NAME

    Your thing name.

    AWS_IOT_ROOT_CA_FILENAME

    Your root CA certificate file name (no path).

    AWS_IOT_CERTIFICATE_FILENAME

    Your certificate file name (no path).

    AWS_IOT_PRIVATE_KEY_FILENAME

    Your private key file name (no path).

    For example:

    // Get from console // ================================================= #define AWS_IOT_MQTT_HOST "a22j5sm6o3yzc5.iot.us-east-1.amazonaws.com" #define AWS_IOT_MQTT_PORT 8883 #define AWS_IOT_MQTT_CLIENT_ID "MyRaspberryPi" #define AWS_IOT_MY_THING_NAME "MyRaspberryPi" #define AWS_IOT_ROOT_CA_FILENAME "root-CA.crt" #define AWS_IOT_CERTIFICATE_FILENAME "device.pem.crt" #define AWS_IOT_PRIVATE_KEY_FILENAME "private.pem.key" // =================================================
  4. Check to see if you have the development tools installed on your device by using this command.

    gcc --version

    If you see the version information for the compiler, you can continue to the next section.

    If you get an error or don't see any compiler information, you'll need to install the build-essential package using this command.

    sudo apt-get install build-essential

    Run the gcc --version command again and confirm that the build tools have been installed and that you are ready to continue.

Build and run the sample application

To run the AWS IoT Device SDK for Embedded C sample applications

  1. Use the makefile in the aws-iot-device-sdk-embedded-c/samples/linux/subscribe_publish_sample directory to compile the subscribe_publish_sample app. From the aws-iot-device-sdk-embedded-c/samples/linux/subscribe_publish_sample directory, enter this command to generate the executable app file.

    make -f Makefile
  2. Run the subscribe_publish_sample app with this command.

    ./subscribe_publish_sample

    You should see output similar to the following:

Your Raspberry Pi is now connected to AWS IoT using the AWS IoT Device SDK for Embedded C.

You can also use the AWS IoT console to view the MQTT messages that the sample app is publishing. For information about how to use the MQTT client in the AWS IoT console, see View MQTT messages with the AWS IoT MQTT client .