Step 4: Create an AWS IoT rule to send an email - AWS IoT Core

Step 4: Create an AWS IoT rule to send an email

An AWS IoT rule defines a query and one or more actions to take when a message is received from a device. The AWS IoT rules engine listens for messages sent by devices and uses the data in the messages to determine if some action should be taken. For more information, see Rules for AWS IoT.

In this tutorial, your Raspberry Pi publishes messages on aws/things/RaspberryPi/shadow/update. This is an internal MQTT topic used by devices and the Thing Shadow service. The Raspberry Pi publishes messages that have the following form:

{
    "reported": {
        "moisture" : moisture-reading,
        "temp" : temperature-reading
    }
}

You create a query that extracts the moisture and temperature data from the incoming message. You also create an Amazon SNS action that takes the data and sends it to Amazon SNS topic subscribers if the moisture reading is below a threshold value.

Create an Amazon SNS rule

  1. In the AWS IoT console, choose Message routing and then choose Rules. If a You don't have any rules yet dialog box appears, choose Create a rule. Otherwise, choose Create rule.

  2. In the Rule properties page, enter a Rule name such as MoistureSensorRule, and provide a short Rule description such as Sends an alert when soil moisture level readings are too low.

  3. Choose Next and configure your SQL statement. Choose SQL version as 2016-03-23, and enter the following AWS IoT SQL query statement:

    
SELECT * FROM '$aws/things/RaspberryPi/shadow/update/accepted' WHERE state.reported.moisture < 400

    This statement triggers the rule action when the moisture reading is less than 400.

    Note

    You might have to use a different value. After you have the code running on your Raspberry Pi, you can see the values that you get from your sensor by touching the sensor, placing it in water, or placing it in a planter.

  4. Choose Next and attach rule actions. For Action 1, choose Simple Notification Service. The description for this rule action is Send a message as an SNS push notification.

  5. For SNS topic, choose the topic that you created in Step 3: Create an Amazon SNS topic and subscription, MoistureSensorTopic, and leave the Message format as RAW. For IAM role, choose Create a new role. Enter a name for the role, for example, LowMoistureTopicRole, and then choose Create role.

  6. Choose Next to review and then choose Create to create the rule.