Serverless design for IoT - An example leverage AWS and GrovePi

AWS announced IOT service in about 2015 and gradually release other relative service (for example: IoT Button) for those who need to tackle with the problem on huge amount of increasing response of "The Things". And it is of course the area which cloud provider what to provide a optional solution.

To demonstrate the benefits of leveraging the serverless design and also utilize the power of AWS cloud. I build an example project combines Serverless design, AWS IoT, Respberry Pi, Grove Sensor system and GrovePI. It will provide in door air quality (office) for me if I want to know that before entering office. So that I can have an excuse to work from somewhere else? :)

In this example, a GrovePi mounts in Raspberry Pi (B+) to control Grove's Air Quality Sensor, HCHO sensor and dust sensor. As a software engineer, I assembled all these inside a paper box. See picture below.

RPi and GrovePi are inside the box. 3 sensors are out there.

Reminder: to use AWS service, the most important things is to read official document. AWS has many different services and there are too many out-of-date articles in somebody's blog. It doesn't mean that authors were wrong, it is just out-of-date. Of course, it is the same in Raspberry Pi and all other 3rd party open source library, try to read official document (or official wiki/blog) to have overall view.

The full implementation and design concerns 

(please check all the project detail in github)

(1) Grove's 3 sensors + GrovePi + Raspberry Pi

   The hardware parts. Check GrovePi's official web site to know how to put them together.

    GrovePi might be the easiest way to program Grove's system from Raspberry Pi, if you have more then 2 device in a machine. However, if you have only one sensor, then just use RPi's GPIO.

(2) AWS IoT service

   Although we didn't program anything in side the hardware, we still need to setup things in AWS IoT service. And of course, it will be better to read at least the tutorial.

Screenshot of AWS IoT Tutorial

   AWS IoT pricing model is counting by message (512bytes). At this moment, about $5 per million message. Which means about $5 per 500MB! This is much more expensive than own a EC2 service to serve device message. However, if you don't need to keep all monitoring data transit in AWS every few seconds and you need only monitoring state changes (maybe a few times per day) then a "Device Shadows" is the best for you.

   In this example, we register a "Thing" named: InDoorSensor1 and the most important thing is to have default Shadow Object as below:

{
  "desired": {
    "welcome": "aws-iot",
    "air quality": 43,
    "action": "wait"
  },
  "reported": {
    "welcome": "aws-iot",
    "action": "wait",
    "air quality": 43
  }
}

   The device will keep sync the Shadow in AWS and if the desired state change to "do", it will (a) do a one time air sensor data collection and then (b) update air quality in Shadow object (c) change to "wait" state. In sort, the Shadow and Device will sync the state (wait or do) and the state's sync is the major function provide from AWS.

(3) AWS IoT Python SDK + GrovePi Python library

AWS provides a few SDK for device, in this project, we use Python to do AWS Cloud access (no matter notification or change Shadow state)

In the Raspberry PI B+, you need to:

    (a) install AWSIoTPythonSDK
    # pip install AWSIoTPythonSDK  (also see here)

    (b) consider the protocol (MQTT vs Websocket). In some environment, the MQTT port might be block. AWS SDK provides MQTT via WebSocket which of course allow broker use port 443.

    (c) certificates: please do read AWS IoT Certificate document if you didn't have experience before

If you use Raspberry PI version B+ 2 or 3, then it will be easy to install nodejs/npm and all other fancy stuff.

(4) IoT Shadow

    The Shadow means an identify object of IoT device. This allows client to change the state of a object and then sync to IoT device. In certain scenario, it allows programmer no need to take care of network error handling or any off line case. However, you still need to fully understand what means exactly the "desired" and "reported" state.
   It is possible to edit Shadow state from AWS admin console direct for testing purpose. (you won't want to do so if you have thousands IoT device).

(5) Lambda, API Gateway

    Supposedly, an application will NOT access specific IoT device, it normally access a service and that service provides information or allow meaningful user actions.
    In this case, a lambda service is simple a python program which can (1) retrieve current state and also current air quality value (2) update state to "do". And as always, the Lambda is behind an API Gateway and which means, potentially, all other application could use this API to access necessary (filtered) information.

see the activity hand draw:

Next Project

Hopefully, I can have more budget to purchase Raspberry PI 3 and also CO2 sensor and then also gather data to draw graphic in D3. Also, I am thinking to use LINE to send air quality information to my colleague or neighborhood.