EXAMPLES

The following tutorials show how to use GUI-O application with ESP32 (and ESP8266) boards in various configuration and communication modes (also supporting push notifications). Tutorial for automatic device pairing also shows how to include SSL/TLS for secure IoT connection.

The same principle of operation can be applied to any other board or device - check out how GUI-O works. To see more examples, visit our forum.

ESP32 & Arduino basic examples

The following examples show basic interaction between GUI-O app and ESP32 module in various communication modes.

ESP32 Bluetooth

Download BasicBluetooth.ino sketch
Follow Basic Bluetooth video tutorial
Additional Boards Manager URLs: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

ESP32 Bluetooth LE

Download BasicBLE.ino sketch (or BasicBLE_NUS.ino for Nordic UART service)
Follow Basic BLE video tutorial
Additional Boards Manager URLs: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

ESP32 MQTT (IoT)

Download BasicMQTT.ino sketch
Follow Basic MQTT video tutorial
Additional Boards Manager URLs: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

ESP32 USB

Download BasicUSB.ino sketch
Follow Basic USB video tutorial
Additional Boards Manager URLs: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

NOTE: In order to connect ESP32 to your Android device, a simple adapter cable is needed (as shown in the figure). Also note that not all Android devices support USB OTG functionality.

ESP32 Ethernet

Download BasicEthernet.ino sketch
Follow Basic Ethernet video tutorial
Additional Boards Manager URLs: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json

ESP32 & Arduino & GUI-O automatic pairing (supports SSL/TLS)

The following example shows how to automatically pair GUI-O app with ESP32 in MQTT (IoT) mode. Although the example uses ESP32-WROOM-32 board, it should be compatible with any other ESP32 board.

GUI-O app always uses SSL/TLS for secure (encrypted) communication. In order to also establish a secure connection from the ESP32 side, use ESP32_GUI-O_pairing_source_SSL_TLS.zip. To establish an unencrypted connection, use ESP32_GUI-O_pairing_source.zip instead (see "Prerequisites" section below).

Prerequisites

Download Arduino IDE
Download ESP32_GUI-O_pairing_libs.zip and extract the archive
Download ESP32_GUI-O_pairing_source.zip or ESP32_GUI-O_pairing_source_SSL_TLS.zip (for secure connection) and extract the archive

Step 1: Add ESP32 board support

Open Arduino IDE
Select "File -> Preferences" and under Additional Boards Manager URLs enter: https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_index.json
Select "Tools -> Board -> Boards manager..."
Search and install "esp32" by Espressif Systems
After installation select "Tools -> Board -> ESP32 Arduino -> ESP32 Dev Module"

Step 2: Include necessary libraries

Select "Sketch -> Include library -> Add .ZIP library..."
Navigate to location, where ESP32_GUI-O_pairing_libs.zip archive was extracted
Select .zip library and confirm (repeat procedure until all .zip libraries are included)

Step 3: Upload the code

Select "File -> Open"
Navigate to location, where ESP32_GUI-O_pairing_source.zip archive was extracted
Select PairingMQTT.ino and confirm
Make sure that ESP32 board is connected to your PC
Make sure that the correct port is selected
Press upload button to start code upload (IMPORTANT NOTE: on some ESP32 boards, the BOOT button must be pressed when the upload starts)
Reset ESP32 board after code upload

Check out the video tutorial below!

Video tutorial of Step 1 - 3

Step 4: Pair GUI-O app with ESP32 board

Open GUI-O app and navigate to settings
Make sure that IoT connection is active (select "Connections -> IoT")
From main settings menu select "Quick pair -> Direct device pairing"
Enter device name (required) and user name (optional) and confirm
Make sure that mobile data plan is disabled and WiFi is enabled
Search and select the WiFi network of the ESP32 (starts with guio_************)
Input password 12345678 (can be changed in "program_ap.cpp" source)
IMPORTANT NOTE: Wait for your device to report that no internet is available and keep WiFi connection to ESP32!
Return to GUI-O app and wait for WiFi network scan
Select your WiFi access point / router and input password
Wait for the pairing procedure to complete and press "Connect"
Wait for successful IoT connection and press the GUI-O initialize button from the home screen

Check out the video tutorial below!

Video tutorial of Step 4

Important notes

ESP32 operates in two WiFi modes: AP (access point - used for pairing) and STA (stationary - used for normal operation)

After first pairing, ESP32 stores the pairing data into its EEPROM and always boots to STA mode when powered on

To clear the pairing data and boot to AP mode, send the following command to ESP32 over the serial port: "!CLEAR_PARAMS\r\n" (see "serialInputHandler()" method in "program_base.cpp" source)

Implement custom handling of GUI-O messages within "mqttReceiveCallback(...)" method in "program_sta.cpp" source

ESP32 & Arduino push notifications

Push notifications support can simply be added to any of the examples above. Usually, push notifications are used to notify the user about some urgent event. For more information regarding push notifications in GUI-O app, see IoT push notifications section in the manual. Also note that the push notifications can be used even if the GUI-O app is not running.

Note that push notifications feature works in the same way as regular IoT messages - if you migrate to your own MQTT broker, no additional setup is required.

Before continuing, it is recommended to try the ESP32 MQTT (IoT) example, since it is used as a reference for this example. Then follow the steps below:

Open GUI-O app settings and navigate to "Info" menu
Make a note of "Application UUID" (you can share the "Application UUID" by clicking on it)
Download Basic_MQTT_push_notification.ino sketch and open it
Use "Application UUID" (from 2.) for the Push topic (keep the /notifications part!)
IMPORTANT NOTE: Don't forget to also generate and set the Out and In topics - see ESP32 MQTT (IoT) example!
Upload the code to ESP32
In GUI-O app settings, navigate to "Quick pair" and press "Connect"
Wait for successful IoT connection and press the GUI-O initialize button from the home screen
Press the Push notification button

Important notes

The "Application UUID" changes if the application is re-installed, or if the application data is deleted. Updating the application does not change the "Application UUID".

In idle mode, the foreground service consumes minor amounts of data. The user is notified about the approximate data usage, when this feature is enabled.

In certain conditions (e.g., low memory), the service can be killed by the host operating system. It is therefore necessary to disable any battery (and similar) optimizations and also enable the "Autostart" feature (if applicable). For reference, see https://dontkillmyapp.com. When the notification feature is enabled, the user is presented with an option to directly open the GUI-O app settings and disable any such optimizations. See the example images of GUI-O app settings menu below.

App settings

App settings -> Other permissions

App settings -> Battery saver

ESP32 & Arduino live image stream (using OV2640 camera)

GUI-O app supports streaming arbitrary grayscale (1 byte per pixel), color (3 bytes per pixel) and jpeg (compressed) images in IoT mode. The images are packed in a binary format in order to optimize the data transmission.

The images can originate from various sources (e.g., live camera image, SD card image, etc.), but before sending the image, it must be formatted in such a way that it can be correctly parsed by the GUI-O app. For more information, see the "Image stream" widget description in the manual and check out the example below using ESP32-S with OV2640 camera.

Before continuing, it is recommended to try the ESP32 MQTT (IoT) example, since it is used as a reference for this example (note that the same Out and In topics can also be used here). Then follow the steps below:

Download BasicMQTT_live_image_stream_jpeg.zip (for jpeg stream) or BasicMQTT_live_image_stream.zip (for grayscale stream) archive and extract it
Open Arduino IDE and load .ino file from the extracted archive
Navigate to "Tools -> Board -> ESP32 Arduino" and select your board (this example uses AI Thinker ESP32-CAM board; also select your camera model within the sketch, if using another board)
Set your router name / password and unique client id
IMPORTANT NOTE: Don't forget to also generate and set the Out and In topics - see ESP32 MQTT (IoT) example!
Upload the code to ESP32 (FTDI programmer can be used for this; note that the GPIO0 pin must be connected to GND during upload)
In GUI-O app settings, navigate to "Quick pair" and press "Connect"
Wait for successful IoT connection and press the GUI-O initialize button from the home screen

Quick test of GUI-O live image stream

Proof of concept of live image stream using a simple Python script. Download the script and try it yourself. Follow the steps below:

In GUI-O app settings, navigate to "Quick pair -> IoT devices" and create a new device
Note the "In" topic of the created device!
Navigate to "Quick pair", press "Connect" and return to GUI-O home screen
Open the Python script and make sure that all imported modules are installed (paho-mqtt and opencv-python)
Set the "pubTopic" variable in the Python script to the "In" topic of the created device
IMPORTANT NOTE: Make sure that the device running the Python script has a camera (e.g., laptop webcam)
Run the Python script (to stream color image instead of grayscale, enable the "useColor" variable within the script)

ESP8266 & Arduino & GUI-O automatic pairing

The following example shows how to automatically pair GUI-O app with ESP8266 in MQTT (IoT) mode. Although the example uses ESP8266 Wemos D1 R1, it should be compatible with any other ESP8266 board.

The procedure is in principle identical to the ESP32 pairing (check the video tutorials under the ESP32 pairing section for additional information). There are some slight differences between ESP32 and ESP8266 pairing procedure - notably when setting up the board and required libraries. Step-by-step procedure is described in the sections below.

VERY IMPORTANT NOTE: The ESP8266 board acts as a bridge. All commands received from the MQTT broker are transmitted over the ESP8266 serial port (Tx). Analogously, all commands that need to be sent to the MQTT broker must be transmitted over the ESP8266 serial port (Rx). This requires an external microcontroller to handle the incoming commands (sent by the GUI-O application) and outgoing commands (received by the GUI-O application).

After programming the ESP8266 with the pairing code, it can be used, for example, to replace an existing USB Serial Bluetooth module to achieve WiFi connectivity. Furthermore, since the ESP8266 works as a standalone board that communicates with the GUI-O application, it can also be used in any other non-Arduino projects.