AWS MQTT Subscribe-Publish Sample#

1. Purpose/Scope#

This application demonstrates how to configure RS9116 as an IoT devices and securely connect to AWS IoT Core to subscribe and publish on a topic.

In this application, RS9116W EVK is configured as Wi-Fi station and connects to an Access Point which has an internet access. After successful Wi-Fi connection, application connects to AWS Core and subscribes to a topic. Publishes a message on subscribed topic and application waits to receive the data published on subscribed topic from the cloud.

Overview of AWS SDK#

AWS IoT Core is a cloud platform which connects devices across AWS cloud services. AWS IoT provides a interface which allows the devices to communicate securely and reliably in bi-directional ways to the AWS touch-points, even when the devices are offline.

The AWS IoT Device SDK allow applications to securely connect to the AWS IoT platform.

Setup Diagram for Device Shadow ExampleSetup Diagram for Device Shadow Example

2. Prerequisites / Setup Requirements#

Before running the application, the user will need the following things to setup.

2.1 Hardware Requirements#

Setup Diagram for Device Shadow ExampleSetup Diagram for Device Shadow Example

2.2 Software Requirements#

3. Application Build Environment#

3.1 Platform#

The Application can be built and executed on below Host platforms

3.2 Host Interface#

  • By default, the application is configured to use the SPI bus for interfacing between Host platforms(STM32F411 Nucleo / EFR32MG21) and the RS9116W EVK.

  • This application is also configured to use the SDIO bus for interfacing between Host platforms(EFM32GG11) and the RS9116W EVK.

3.3 Project Configuration#

The Application is provided with the project folder consists of Keil and Simplicity studio (ssl) project files.

  • Keil project :

    • The Keil can be executed on STM32 platform.

    • Project Path : <SDK>\examples\snippets\wlan\cloud_apps\aws_iot\mqtt\projects\aws_iot_mqtt-nucleo-f411re.uvprojx

  • Simplicity Studio :

    • The Simplicity Studio project is used to evaluate the application on EFR32MG21.

    • If the Radio Board is BRD4180A or BRD4181A, then access the path <SDK>\examples\snippets\wlan\cloud_apps\aws_iot\mqtt\projects\aws_iot_mqtt-brd4180a-mg21.slsproj

    • If the Radio Board is BRD4180B or BRD4181B, then access the path <SDK>\examples\snippets\wlan\cloud_apps\aws_iot\mqtt\projects\aws_iot_mqtt-brd4180b-mg21.slsproj

    • EFM32GG11 platform

      • The Simplicity Studio project is used to evaluate the application on EFM32GG11.

        • Project path:<SDK>/examples/snippets/wlan/cloud_apps\aws_iot\mqtt/projects/aws_iot_mqtt-brd2204a-gg11.slsproj

3.4 Bare Metal/RTOS Support#

This application supports bare metal and RTOS environment. By default, the application project files (Keil and Simplicity studio) are provided with bare metal configuration in the SDK.

4. Application Configuration Parameters#

The application can be configured to suit user requirements and development environment. Read through the following sections and make any changes needed.

4.1 Open rsi_subscribe_publish_sample.c file#

4.1.1 User must update the below parameters#

SSID refers to the name of the Access point.

#define SSID                           "SILABS_AP"

SECURITY_TYPE refers to the type of security. In this application STA supports Open, WPA-PSK, WPA2-PSK securities.

Valid configuration is:

  • RSI_OPEN - For OPEN security mode

  • RSI_WPA - For WPA security mode

  • RSI_WPA2 - For WPA2 security mode

#define SECURITY_TYPE                   RSI_WPA2

PSK refers to the secret key if the Access point configured in WPA-PSK/WPA2-PSK security modes.

#define PSK                             "1234567890"

The following parameters are configured if OS is used. Application task should be of low priority

#define RSI_MQTT_CLIENT_TASK_PRIORITY                   1

Driver task should have the highest priority among all threads

#define RSI_DRIVER_TASK_PRIORITY                 2

MQTT Task stack size is configured by this macro

#define RSI_MQTT_CLIENT_TASK_STACK_SIZE           512 * 2

Driver Task stack size is configured by this macro

#define RSI_DRIVER_TASK_STACK_SIZE         512 * 2

GLOBAL_BUFF_LEN refers the memory length for driver

#define GLOBAL_BUFF_LEN                      15000

To configure IP address

DHCP_MODE refers whether IP address configured through DHCP or STATIC

#define DHCP_MODE                        1

To configure MQTT Topic

RSI_MQTT_TOPIC refres to the topic to which the device subscribes and publishes

#define RSI_MQTT_TOPIC          "$aws/things/Test_IoT/shadow/update"

Note: To configure, STA IP address through DHCP then set DHCP_MODE to "1" and skip configuring the following DEVICE_IP, GATEWAY and NETMASK macros. (Or) To configure, STA IP address through STATIC then set DHCP_MODE macro to "0" and configure following DEVICE_IP, GATEWAY and NETMASK macros.

The IP address needs to be configuring to the RS9116W EVk should be in long format and in little endian byte order.

Example: To configure "192.168.10.10" as IP address, update the macro DEVICE_IP as 0x0A0AA8C0.

#define DEVICE_IP                        0X0A0AA8C0

IP address of the gateway should also be in long format and in little endian byte order

Example: To configure "192.168.10.1" as Gateway, update the macro GATEWAY as 0x010AA8C0

#define GATEWAY                          0x010AA8C0

IP address of the network mask should also be in long format and in little endian byte order.

Example: To configure "255.255.255.0" as network mask, update the macro NETMASK as 0x00FFFFFF

#define NETMASK                          0x00FFFFFF

4.2 Open rsi_wlan_config.h file. User can also modify the below parameters as per their needs and requirements.#

#define CONCURRENT_MODE                  RSI_DISABLE
#define RSI_FEATURE_BIT_MAP              FEAT_SECURITY_OPEN
#define RSI_TCP_IP_BYPASS                RSI_DISABLE
#define RSI_TCP_IP_FEATURE_BIT_MAP       (TCP_IP_FEAT_DHCPV4_CLIENT|TCP_IP_FEAT_SSL |TCP_IP_FEAT_DNS_CLIENT)
#define RSI_CUSTOM_FEATURE_BIT_MAP       FEAT_CUSTOM_FEAT_EXTENTION_VALID
#define RSI_EXT_CUSTOM_FEATURE_BIT_MAP   (EXT_FEAT_256K_MODE | BIT(1) | BIT(3) | BIT(27))
#define RSI_BAND                         RSI_BAND_2P4GHZ

Power save configuration

  • By default, the application is configured without power save.

#define ENABLE_POWER_SAVE              0

  • If user wants to run the application in power save, modify the below macro.

#define ENABLE_POWER_SAVE              1

4.3 Configure below parameters in aws_iot_config.h file#

//AWS Host name 
#define AWS_IOT_MQTT_HOST          "xxxxxxxxxxxxx-ats.iot.us-east-2.amazonaws.com" 

//default port for MQTT
#define AWS_IOT_MQTT_PORT          "8883"

// MQTT client ID should be unique for every device  
#define AWS_IOT_MQTT_CLIENT_ID     "Test_IoT"

4.4 Setting up Security Certificates#

To authenticate and securely connect with AWS, your Wi-Fi device requires a unique x.509 security certificate and private key, as well as a CA certificate which is used to verify the AWS server. Security credentials need to be converted into a C-array rather than PEM format provided by AWS; they also need to be added to your project.

The WiSeConnect SDK provides a conversion script (written in Python 3) to make the conversion straightforward. The script is provided in the SDK 'resources' directory and is called certificate_to_array.py.

To convert the device certificate and private key to C arrays, open a system command prompt and use the script as indicated in the following examples.

$> python3 certificate_to_array.py <input filename> <output arrayname>

For example:
$> python3 certificate_to_array.py d8f3a44d3f.cert.pem    aws_client_certificate
$> python3 certificate_to_array.py d8f3a44d3f.private.key aws_client_private_certificate

After running the script on the certificate and private key, two new files are created.

aws_client_certificate.pem.crt.h
aws_client_private_key.pem.key.h

Before proceeding, copy both of the new files to the WiSeConnect directory: <SDK>/resources/certificates
Go ahead and overwrite any existing files with the same name in that directory, the originals are not needed.

The Root CA certificate used by your Wi-Fi device to verify the AWS server is already included in the WiSeConnect SDK; no additional setup is required. For reference, Amazon uses Starfield Technologies to secure the AWS website, the WiSeConnect SDK includes the Starfield CA Certificate.

NOTE : For AWS connectivity, StarField Root CA Class 2 certificate has the highest authority being at the top of the signing hierarchy.

The StarField Root CA Class 2 certificate is an expected/required certificate which usually comes pre-installed in the operating systems and it plays a key part in certificate chain verification when a device is performing TLS authentication with the IoT endpoint.

On RS9116 device, we do not maintain root CA trust repository due to memory constraints, so it is mandatory to load StarField Root CA Class 2 certificate for successful mutual authentication to AWS server.

The certificate chain sent by AWS server is as below: id-at-commonName=Amazon,id-at-organizationalUnitName=Server CA 1B,id-at-organizationName=Amazon,id-at-countryName=US id-at-commonName=Amazon Root CA 1,id-at-organizationName=Amazon,id-at-countryName=US id-at-commonName=Starfield Services Root Certificate Authority ,id-at-organizationName=Starfield Technologies, Inc.,id-at-localityName=Scottsdale,id-at- stateOrProvinceName=Arizona,id-at-countryName=US)

On RS9116 to authenticate the AWS server, firstly Root CA is validated (validate the Root CA received with the Root CA loaded on the device). Once the Root CA is validation is successful , other certificates sent from the AWS server are validated. RS9116 don't authenticate to AWS server if intermediate CA certificates are loaded instead of StarField Root CA Class 2 certificate and would result in Handshake error. StarField Root CA Class 2 certificate is at https://certs.secureserver.net/repository/sf-class2-root.crt

Reference links : https://aws.amazon.com/blogs/security/how-to-prepare-for-aws-move-to-its-own-certificate-authority/

5. Testing the Application#

User has to follow the below steps for the successful execution of the application.

5.1 Loading the RS9116W Firmware#

Refer Getting started with a PC to load the firmware into RS9116W EVK. The firmware file is located in <SDK>/firmware/

5.2 Building the Application on Host Platform#

5.2.1 Using STM32#

Refer Getting started with STM32

  • Open the project <SDK>\examples\snippets\wlan\cloud_apps\aws_iot\mqtt\projects\aws_iot_mqtt-nucleo-f411re.uvprojx

  • Build and Debug the project.

  • Check for the RESET pin:

    • If RESET pin is connected from STM32 to RS9116W EVK, then user need not press the RESET button on RS9116W EVK before Free run.

    • If RESET pin is not connected from STM32 to RS9116W EVK, then user need to press the RESET button on RS9116W EVK before Free run.

  • Free run the project.

  • Then continue the common steps from Section 5.3

5.2.2 Using EFX#

Refer Getting started with EFX32, for settin-up EFR & EFM host platforms

  • Open Simplicity Studio and import the EFR32/EFM32 project <SDK>\examples\snippets\wlan\cloud_apps\aws_iot\mqtt\projects

    • Select the appropriate .slsproj as per Radio Board type mentioned in Section 3.3 for EFR32 board. (or)

    • Select the *.brd2204a-gg11.slsproj for EFM32GG11 board.

  • Compile and flash the project in to Host MCU

  • Debug the project

  • Check for the RESET pin:

    • If RESET pin is connected from EFX32 to RS9116W EVK, then user need not press the RESET button on RS9116W EVK before free run

    • If RESET pin is not connected from EFX32 to RS9116W EVK, then user need to press the RESET button on RS9116W EVK before free run

  • Free run the project

  • Then continue the common steps from Section 5.3

5.3 Common Steps#

  1. Configure the Access point with Internet connection in OPEN/WPA-PSK/WPA2-PSK mode to connect module in STA mode.

  2. Configure the application with the configurations mentioned in Section 4 for the AWS IoT Thing created. [ Refer to Appendix on how to create a Thing ]

  3. Application will Subscribe to the RSI_MQTT_TOPIC and Publishes message "{"state":{"desired":{"toggle":1}}}" to the same topic.

It receives the publish message sent, as it has subscribed to the same topic.

Upon receiving the Publish message it processes the message "{"state":{"desired":{"toggle":1}}}" and toggles LED.

  1. The Terminal Logs appears as shown below

Console logsConsole logs

  1. You should be able to see the LED toggling on the board

Appendix#

Create an AWS Thing#

Create a thing in the AWS IoT registry to represent your IoT Device.

  • In the AWS IoT console, in the navigation pane, choose Manage, and then choose Things.

AWS consoleAWS console

  • If a You don't have any things yet dialog box is displayed, choose Register a thing. Otherwise, choose Create.

  • Click on Create.

AWS ThingAWS Thing

  • On the Creating AWS IoT things page, choose Create a single thing.

AWS thing creationAWS thing creation

  • On the Add your device to the device registry page, enter a name for your IoT thing (for example, Test_IoT), and then choose Next. You can't change the name of a thing after you create it. To change a thing's name, you must create a new thing, give it the new name, and then delete the old thing.

Add DeviceAdd Device

  • On the Add a certificate for your thing page, choose Create certificate.

Add certificateAdd certificate

  • Choose the Download links to download the certificate, private key, and root CA certificate.

    Warning: This is the only instance you can download your certificate and private key. Make sure to save them safely.

  • Choose Activate.

  • Choose Attach a policy.

Attach PolicyAttach Policy

  • Choose the Policy created and then choose Register Thing.

    Note : If you don't have any policy created, follow the steps in Create Policy section in the below and then choose the created Policy

  • View list of devices as shown

Register ThingRegister Thing

Create Policy#

  1. Navigate to AWS IoT console

  2. Choose Policies under Secure

Register ThingRegister Thing

  1. Click on Create

Register ThingRegister Thing

  1. Give the Name to your Policy, Fill Action and Resource ARN as shown in below image, Click on Allow under Effect and click Create

Register ThingRegister Thing

Compressed Debug Logging#

To enable the compressed debug logging feature please refer to Logging User Guide