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Handle IoT system state wherever utilizing AWS IoT System Shadow service and AWS IoT Greengrass


Web of Issues (IoT) builders usually must implement a strong mechanism for managing IoT system state both regionally or remotely. A typical instance is a brilliant residence radiator, an IoT system the place you should use the built-in management panel to regulate the temperature (system state), or set off temperature adjustment messages remotely from a software program software operating within the cloud.

You may rapidly construct this mechanism by utilizing the AWS IoT System Shadow service. The AWS IoT System Shadow service could make a tool’s state accessible to what you are promoting logic, even within the case of intermittent community connection.

As well as, to effectively handle your system’s software program lifecycle and speed up your growth efforts, you should use AWS IoT Greengrass together with its pre-built elements. AWS IoT Greengrass is an open-source edge runtime and cloud service for constructing, deploying, and managing system software program. One of many elements of AWS IoT Greengrass is the shadow supervisor, which permits the native shadow service in your core system. The native shadow service permits elements to make use of interprocess communication (IPC) to work together with native shadows. The shadow supervisor element manages the storage of native shadow paperwork, and in addition handles synchronization of native shadow states with the AWS IoT System Shadow service.

On this weblog submit, I’m utilizing AWS IoT System Shadow service and AWS IoT Greengrass along with a Raspberry Pi and Sense HAT {hardware} to simulate a wise residence radiator. This demonstration makes use of a single digit quantity (0 – 9) to simulate the output energy. This quantity is the system state that we wish to handle from wherever, native and distant. The person can change this quantity by way of an area {hardware} change (the built-in joystick on the Sense HAT) in addition to remotely from a cloud-based software.

The Raspberry Pi exhibits the quantity on the Sense HAT LED show, indicating the radiator output energy. The person can push up on the joystick on the Sense HAT to extend the quantity (or push all the way down to lower it).

Raspberry Pi simulating home radiator
Determine 1. Raspberry Pi – simulating residence radiator

Architecture overview
Determine 2. Structure overview

By following this weblog submit, you possibly can rapidly begin constructing and testing your IoT options for managing your system’s state wherever.


To comply with by way of this weblog submit, you have to:


Software program:


Step 1: Set up and configure the AWS IoT Greengrass core software program on the Raspberry Pi.

In an effort to make your Raspberry Pi as an AWS IoT Greengrass core system, comply with step 1 to step 3 within the AWS IoT Greengrass Getting began doc. I created the system with the next configuration:

  • Core system identify: PiWithSenseHat
  • Factor group: RaspberryPiGroup

Now you must have the ability to see this system in your AWS console.

AWS IoT Greengrass core device in console
Determine 3. AWS IoT Greengrass core system in console

Step 2: Deploy prebuilt AWS IoT Greengrass elements to the system

The following step is to deploy prebuilt AWS IoT Greengrass elements to the system. AWS IoT Greengrass gives and maintains a set of prebuilt elements that may speed up our growth. On this demonstration, I’m deploying the next elements:

  • greengrass.Cli:
    Supplies an area command-line interface that you should use on core units to develop and debug elements regionally
  • greengrass.ShadowManager
    Permits the native shadow service in your core system and handles synchronization of native shadow states with the AWS IoT System Shadow service
  • greengrass.LocalDebugConsole (elective)
    Supplies an area dashboard that shows details about your AWS IoT Greengrass core units and its elements


  1. Go to AWS IoT Greengrass console
  2. Navigate to Deployment in Greengrass units, create a brand new deployment
  3. Deployment goal might be both Factor group RaspberryPiGroup, or Core system
  4. Choose these 3 elements from Public elements

Select the prebuilt components
Determine 4. Choose the prebuilt elements

  1. Configure aws.greengrass.ShadowManager element

In Configure elements step, choose aws.greengrass.ShadowManager, then click on Configure element

Configure aws.greengrass.ShadowManager
Determine 5. Configure aws.greengrass.ShadowManager

  1. Arrange element model and configuration json of aws.greengrass.ShadowManager

Configure aws.greengrass.ShadowManager details
Determine 6. Configure aws.greengrass.ShadowManager – particulars

  • Model: 2.3.1
  • Configuration to merge:  
  "synchronize": {
    "coreThing": {
      "traditional": true,
      "namedShadows": [
    "shadowDocuments": [],
    "route": "betweenDeviceAndCloud"
  "rateLimits": {
    "maxOutboundSyncUpdatesPerSecond": 100,
    "maxTotalLocalRequestsRate": 200,
    "maxLocalRequestsPerSecondPerThing": 20
  "shadowDocumentSizeLimitBytes": 8192

The json configuration synchronizes a named shadow, referred to as NumberLEDNamedShadow on this instance, in each instructions, betweenDeviceAndCloud possibility. In your real-world software, you possibly can use a number of named shadows, and with 1 approach or bi-directional synchronization. Test the main points of the aws.greengrass.ShadowManager in its doc.

  1. Full the Create Deployment wizard to complete the deployment.

On the finish of the Step 2, the Raspberry Pi is able to synchronize a named shadow NumberLEDNamedShadow between system and cloud, by utilizing AWS IoT Greengrass core software program and the prebuilt element.

Step 3: Create AWS IoT Greengrass elements for simulating good residence radiator with native management

Now create two AWS IoT Greengrass elements for simulating a wise residence radiator with native management. We are able to leverage interprocess communication (IPC) for the inner communication between the elements. In case you are not conversant in tips on how to construct customized AWS IoT Greengrass elements, please comply with step 4 within the Getting began doc. On this weblog, we create and take a look at them regionally.

  1. Element instance.sensehat.joystick: Seize the occasions from the joystick and publish the occasions to an IPC subject “ipc/joystick” (It was outlined as a variable within the recipe).
  2. Element instance.sensehat.led: Subscribe the IPC subject “ipc/joystick”, replace the native shadow and the Sense HAT LED show.

3.1 Create element com.instance.sensehat.joystick

This element is publishing occasions of the built-in joystick to AWS IoT Greengrass core IPC. The occasion is like:


You will discover the element recipe and artifact from weblog supply code repo. As a substitute of arduous coding the IPC subject within the supply code, it’s outlined within the recipe as a variable.

3.2 Create element com.instance.sensehat.led

Now create the second element named com.instance.sensehat.led. You will discover the element recipe and artifact within the supply code repo. Within the recipe it defines the entry permission to IPC and shadow paperwork.

This element:

  • Maintains a quantity as system state, and shows it on LED
  • Subscribes to joystick occasion subject through IPC
  • Primarily based on the obtained joystick occasion, improve/lower the quantity
  • Periodically checks the shadow. If there’s a new quantity within the shadow doc, replace the system with that quantity.

Workflow of com.example.sensehat.led component
Determine 7. Workflow of com.instance.sensehat.led element

Demo: Handle the system state in motion

Now the Raspberry Pi as simulator is prepared to be used.

It responds to 2 varieties of occasions:

  • New joystick occasion: Management the system regionally
  • New cloud shadow doc: Management the system remotely

Logic to control the device either locally or remotely
Determine 8: Logic to manage the system both regionally or remotely

To see the system shadow in motion:

  1. Go to AWS IoT Greengrass console
  2. Navigate to Issues, choose PiWithSenseHat
  3. In System Shadows, you could find the NumberLEDNamedShadow. Word that you don’t want to manually create this shadow. When system experiences again the shadow for the primary time, it should create it for you whether it is lacking.

locate the device shadow in AWS console
Determine 9. find the system shadow in AWS console

Demo 1: Replace the system regionally by utilizing joystick

  1. Use the joystick to extend/lower the quantity regionally (The preliminary quantity was 6. I firstly deceased it to 0, then elevated it to 2).
  2. Observe the system shadow doc is up to date in actual time in AWS console. The change is sync to the cloud shadow in the true time.
    • standing is modified to “system up to date by native”
    • quantity is modified to the brand new worth from native

Using joystick to update the number
Determine 10: Utilizing joystick to replace the quantity, and report the brand new worth to cloud in actual time

Demo 2: Replace the system remotely by updating system shadow doc in cloud

  1. At first of this demo, the system LED was displaying 0, and system shadow doc was
      "state": {
        "desired": {
          "quantity": 0
        "reported": {
          "standing": "system is up to date by native",
          "quantity": 0
  2. In AWS IoT Core console, Edit the shadow doc with the next Json (you possibly can skip the “reported” part), then click on Replace
      "state": {
        "desired": {
  1. Observe the Raspberry Pi LED updates the quantity. The change is pushed from cloud to native system. Now the system is displaying quantity 9:
    • standing is modified to “system up to date by shadow”
    • quantity is modified from 0 to 9.

Update the device remotely by updating device shadow document in cloud
Determine 11. Replace the system remotely by updating system shadow doc in cloud

Because the show quantity may be up to date both by native joystick or remotely from AWS console, the newest replace takes priority. Due to this fact when the replace is finished regionally, it is necessary to set the “desired” worth again to distant shadow in cloud, so the distant shadow is aware of the brand new “desired” worth and won’t replace it within the subsequent shadow sync cycle. See extra on the doc device-shadow-empty-fields.

Cleansing up

  • Delete/disable IAM person which you used for putting in AWS IoT Greengrass core software program in Raspberry Pi
  • Underneath AWS IoT console, navigate to Greengrass units
    • In Core System choose the system PiWithSenseHat and Hit delete on prime proper.
    • In Factor teams delete RaspberryPiGroup
  • Take away these two customized elements from Raspberry Pi
    • Run the next instructions within the terminal on Raspberry Pi
      • sudo /greengrass/v2/bin/greengrass-cli --ggcRootPath /greengrass/v2 deployment create --remove "com.instance.sensehat.led"
      • sudo /greengrass/v2/bin/greengrass-cli --ggcRootPath /greengrass/v2 deployment create --remove "com.instance.sensehat.joystick"
    • Uninstall AWS IoT Greengrass core software program from Raspberry Pi
      • Observe the steps in this doc to uninstall the AWS IoT Greengrass core software program out of your Raspberry Pi.


On this submit, you discovered tips on how to use AWS IoT System Shadow service and AWS IoT Greengrass to construct a strong answer for managing IoT system state, whether or not it’s finished regionally or remotely. Now you can focus by yourself enterprise logic, and let these two AWS providers to do the heavy lifting for managing system state wherever. At present these two customized elements are created and deployed regionally within the system. The following step might be making them accessible in AWS IoT Greengrass, so you possibly can deploy them to extra units. In an effort to that, you possibly can comply with step 5 and step 6 in AWS IoT Greengrass doc.

Concerning the writer

Feng Lu

Feng Lu is a Senior Options Architect in AWS with 18 years skilled expertise. He’s obsessed with serving to organizations to craft scalable, versatile, and resilient architectures that deal with their enterprise issues. At present his focus is on connecting the bodily world and cloud with IoT applied sciences, and uniting computing/AI capability to make our bodily atmosphere smarter and higher.



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