Embedded Devices

Hardware Requirements


For the memory this example requires:

  • Dynamic memory(DRAM) : 30 - 50kB
  • Flash Memory : 150 - 200kB


In3 client needs to have a reliable internet connection to work properly, so your hardware must support any network interface or module that could give you access to it. i.e Bluetooth, Wifi, ethernet, etc.

Incubed with ESP-IDF

Use case example: Airbnb Property access

A smart door lock that grants access to a rented flat is installed on the property. It is able to connect to the Internet to check if renting is allowed and that the current user is authorized to open the lock.

The computational power of the control unit is restricted to the control of the lock. And it is also needed to maintain a permanent Internet connection.

You want to enable this in your application as an example of how in3 can help you, we will guide through the steps of doing it, from the very basics and the resources you will need

Hardware requirements

_images/embedded_esp.pngfrom https://docs.espressif.com/projects/esp-idf/en/stable/get-started/

  • ESP32-DevKitC V4 or similar dev board
  • Android phone
  • Laptop MAC, Linux, Windows
  • USB Cable

Software requirements

  • In3 C client
  • Esp-idf toolchain and sdk, (please follow this guide) and be sure on the cloning step to use release/v4.0 branch

git clone -b release/v4.0 --recursive https://github.com/espressif/esp-idf.git

  • Android Studio
  • Solidity smart contract: we will control access to properties using a public smart contract, for this example, we will use the following template
  • Silab USB drivers
pragma solidity ^0.5.1;

contract Access {
    uint8 access;
    constructor() public  {
        access = 0;
    function hasAccess() public view returns(uint8) {
        return access;
    function setAccess(uint8 accessUpdate) public{
        access = accessUpdate;

How it works

_images/embedded_diagram.pngsequence diagram

In3 will support a wide range of microcontrollers, in this guide we will use well-known esp32 with freertos framework, and an example android app to interact with it via Wifi connection.

Instalation instructions

  1. Clone the repo

git clone --recursive https://github.com/slockit/in3-devices-esp

  1. Deploy the contract with your favorite tool (truffle, etc) or use our previusly deployed contract on goerli, with address 0x36643F8D17FE745a69A2Fd22188921Fade60a98B
  2. Config your SSID and password inside sdkconfig file sdkconfig.defaults
  1. Build the code idf.py build
  2. Connect the usb cable to flash and monitor the serial output from the application.

idf.py flash && idf.py monitor

after the build finishes and the serial monitor is running you will see the configuration and init logs.

  1. Configure the ip address of the example, to work with: Take a look at the inital output of the serial output of the idf.py monitor command, you will the ip address, as follows
I (2647) tcpip_adapter: sta ip:, mask:, gw:
I (2647) IN3: got ip:

take note if your ip address which will be used in the android application example.

  1. Clone the android repository, compile the android application and install the in3 demo application in your phone.

git clone https://github.com/slockit/in3-android-example

  1. Modify the android source changing ip address variable inside kotlin source file MainActivity.kt, with the IP address found on step 6.

(L:20) private const val ipaddress = "http://192.168.xx.xx"

  1. If you want to test directly without using android you can also do it with the following http curl requests:
  • curl -X GET http://slock.local/api/access
  • curl -X GET http://slock.local/api/retrieve

we need 2 requests as the verification process needs to be executed in asynchronous manner, first one will trigger the execution and the result could be retrieved with the second one

Incubed with Zephyr

….(Comming soon)