#Zerynth: ESP32 & Google IoT Core - Part 2: Getting data from Smart Power Outlets

This part 2 of the tutorial will allow you to get data from the smart power outlets and send it to the Google Cloud Platform (GCP) throught the Google IoT Core and using an ESP32 programmed with Zerynth (Python). This data is not usually available to the user (directly, you need to use the power outlet application), and it is sent to the company servers.

If you want to check, if your power outlets are compatible for this tutorial, they should have the port 6668 opened. To check that:

>>> nmap <<ip-address>> -p 6668
[...]
Host is up (0.13s latency).

PORT     STATE SERVICE
6668/tcp open  irc

If the answer is as shown above, the port is opened. If you don't have the nmap application and you are on Windows, look at the Nmap Network Scanning tool. On Ubuntu type on a terminal sudo apt-get install nmap.

I've already published a tutorial to control the smart power outlets using MicroPython here, but as I said in part 1, MicroPython does not support JSON Web Tokens (JWT) yet, and thus it is not possible to connect to the GCP. I've tried to develop the connection again, but I needed some Elliptic Curve Cryptography. I had a hard work trying it, but I couldn't finish it :(. I need more knowledge about cryptography. Then, I use Zerynth again.

Using Zerynth, I wasn't able to control the devices because I didn't find any AES cryptography class that worked on it. It is possible to adapt the MicroPython version of AES (check here), but for a first try, I needed only the status data, and I didn't want to control the switches. Thus, the localKey is not needed. I included the variable on the main.py file, but you can leave it blank, or you can write what you want. But you need the devId value, to get that, check the Key extraction section of this post.

Hardware and Software

DIY

You can program the ESP32 using Zerynth as described on the part 1 of this tutorial. The steps to run this code:

1. Clone or download the repository: https://github.com/lemariva/zerynth-smart-outlet
2. Configure the:
   • ssid_: Wi-Fi SSID, where your power outlet is also connected.
   • wp2_pass: WPA2 for the selected Wi-Fi.
   • DEVICE_ID_HERE: use the obtained devId. Check here.
   • IP_ADDRESS: IP address of the power outlet on your LAN. You can get that from your Wi-Fi router.
   • LOCAL_KEY: write what you want, or use the localKey. Check here.

The following data is available:

• a json like the following (it depends on the power outlet):

  {
  'dps': 
      {
       '25': 1165, 
       '24': 17857, 
        '9': 0, 
       '22': 623, 
       '23': 30606, 
        '1': True, 
       '21': 1, 
       '20': 2284, 
       '18': 75, 
       '19': 86
       }, 
    'devId': '80023151840d8e4bbef9'
    }

  in my case, the parameter:

  • 1 : represents the actual status (True=On, False=Off).
  • 18: is the actual mAh consume.
  • 19: is the actual W consume.
  • 20: is the actual V.

  If you have more information about the other parameters, leave me a comment.

Now, I have all the data that I wanted. The next steps are going to be on the GCP to process the data.