Services or capabilities described in Amazon Web Services documentation might vary by Region. To see the differences applicable to the China Regions, see Getting Started with Amazon Web Services in China (PDF).

Prerequisites for OTA updates using MQTT

This section describes the general requirements for using MQTT to perform over-the-air (OTA updates).

Minimum requirements

Configurations

Beginning with version 201912.00, FreeRTOS OTA can use either the HTTP or MQTT protocol to transfer firmware update images from Amazon IoT to devices. If you specify both protocols when you create an OTA update in FreeRTOS, each device will determine the protocol used to transfer the image. See Prerequisites for OTA updates using HTTP for more information.

By default, the configuration of the OTA protocols in ota_config.h is to use the MQTT protocol.

Device specific configurations

None.

Memory usage

When MQTT is used for data transfer, no additional memory is required for the MQTT connection because it's shared between control and data operations.

Device policy

Each device that receives an OTA update using MQTT must be registered as a thing in Amazon IoT and the thing must have an attached policy like the one listed here. You can find more information about the items in the "Action" and "Resource" objects at Amazon IoT Core Policy Actions and Amazon IoT Core Action Resources.

{
    "Version": "2012-10-17",
    "Statement": [
        {
            "Effect": "Allow",
            "Action": "iot:Connect",
            "Resource": "arn:partition:iot:region:account:client/${iot:Connection.Thing.ThingName}"
        },
        {
            "Effect": "Allow",
            "Action": "iot:Subscribe",
            "Resource": [
                "arn:partition:iot:region:account:topicfilter/$aws/things/${iot:Connection.Thing.ThingName}/streams/*",
                "arn:partition:iot:region:account:topicfilter/$aws/things/${iot:Connection.Thing.ThingName}/jobs/*"
            ]
        },
        {
            "Effect": "Allow",
            "Action": [
                "iot:Publish",
                "iot:Receive"
            ],
            "Resource": [
                "arn:partition:iot:region:account:topic/$aws/things/${iot:Connection.Thing.ThingName}/streams/*",
                "arn:partition:iot:region:account:topic/$aws/things/${iot:Connection.Thing.ThingName}/jobs/*"
            ]
        }
    ]
}