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Writer's pictureRamesh G

eBike demo GUI with ESP32 and 3.5inch TFT display

Updated: Nov 16

Creating a demo GUI for an eBike using an ESP32 and a 3.5-inch TFT display can be an exciting project! Below is a high-level overview of how to set up your project, including the necessary components, libraries, and a basic example of how to structure your code.


Components Required

ESP-32 Module (38Pin)

3.5 inch TFT ILI9488 SPI Interface Module 480x320 with Touch Screen Display

10k Potentiometer -2nos

Jumper Wires


Circuit Diagram


3.5inch TFT display


TFT refer blog:


In the VCC pin, you can either use 5V or 3.3V depending upon if your J1 connection is open or closed,

J1 = open=5V; J1=close=3.3V.




LVGL refer:


Hardware Requirements

  1. ESP32 Board: Any variant should work, but make sure it has enough GPIO pins.

  2. TFT LCD Touchscreen: Common models include ILI9488

  3. Connecting Wires: Jumper wires for connections.

  4. Breadboard (optional): For easier connections.


Software Requirements

  1. Arduino IDE: Make sure you have the latest version.

    Select “File>Preferences>settings>Additional Boards Manager URLs” to fill the link.

    Here are the steps to install the ESP32 board in Arduino IDE: 


    1. Open the Arduino IDE  

    2. Select File and then Preferences 

    3. Find the Additional Board Manager URLs field and activate the text box 

    4. Add the URL to the field 

    5. Click OK to save the changes 

       

     https://raw.githubusercontent.com/espressif/arduino-esp32/gh-pages/package_esp32_dev_index.json,

    https://arduino.esp8266.com/stable/package_esp8266com_index.json,

    https://espressif.github.io/arduino-esp32/package_esp32_index.json




  2. LVGL Library: Available through the Library Manager in the Arduino IDE.


  3. Touch Driver Library: Depending on your touchscreen (e.g., TFT_eSPI)

    Configuring LVGL

    1. LVGL Configuration: You may need to configure LVGL for your specific display and touch screen. Create a lv_conf.h file or modify the existing one in the LVGL library folder:

      • Set LVGL_DISPLAY_HOR_RES and LVGL_DISPLAY_VER_RES to match your display's resolution.

      • Configure the display and touch input settings based on your library (e.g., TFT_eSPI settings).


    2. TFT_eSPI Configuration:

      A feature rich Arduino IDE compatible graphics and fonts library for 32-bit processors. The library is targeted at 32-bit processors, it has been performance optimised for RP2040, STM32, ESP8266 and ESP32 types, other 32-bit processors may be used but will use the slower generic Arduino interface calls. The library can be loaded using the Arduino IDE's Library Manager. Direct Memory Access (DMA) can be used with the ESP32, RP2040 and STM32 processors with SPI interface displays to improve rendering performance. DMA with a parallel interface (8 and 16-bit) is only supported with the RP2040.

       Go to the TFT_eSPI library folder and open the User_Setup.h file to configure the pins according to your wiring.

    3. Wiring the TFT Display

TFT Pin  ESP32 Pin

VCC       3.3V

GND      GND

CS          GPIO 5

RESET   GPIO EN

DC/RS  GPIO 17

SDI(MOSI)          GPIO 23

SCK       GPIO 18

LED       3.3V (or PWM pin for brightness)


Wiring the Touchscreen (e.g., TFT_espi)

Touch Pin           ESP32 Pin

T_CS     GPIO 16

T_IRQ    GPIO 21

T_DOUT              GPIO 19

T_DIN   GPIO 23

T_CLK   GPIO 18

4. UI Library: User Interface (e.g., UI)





Arduino Code

Here’s a basic example to initialize the display and create a simple button using LVGL:




######################################################################

#include <lvgl.h>

#include <TFT_eSPI.h>

#include <ui.h>


/*Don't forget to set Sketchbook location in File/Preferences to the path of your UI project (the parent foder of this INO file)*/


/*Change to your screen resolution*/

static const uint16_t screenWidth  = 480;

static const uint16_t screenHeight = 320;


static lv_disp_draw_buf_t draw_buf;

static lv_color_t buf[ screenWidth * screenHeight / 10 ];


TFT_eSPI tft = TFT_eSPI(screenWidth, screenHeight); /* TFT instance */


#if LV_USE_LOG != 0

/* Serial debugging */

void my_print(const char * buf)

{

    Serial.printf(buf);

    Serial.flush();

}


/* Display flushing */

void my_disp_flush( lv_disp_drv_t disp, const lv_area_t area, lv_color_t *color_p )

{

    uint32_t w = ( area->x2 - area->x1 + 1 );

    uint32_t h = ( area->y2 - area->y1 + 1 );


    tft.startWrite();

    tft.setAddrWindow( area->x1, area->y1, w, h );

    tft.pushColors( ( uint16_t  )&color_p->full, w h, true );

    tft.endWrite();


    lv_disp_flush_ready( disp );

}


/*Read the touchpad*/

void my_touchpad_read( lv_indev_drv_t  indev_driver, lv_indev_data_t  data )

{

    uint16_t touchX = 0, touchY = 0;


    bool touched = false;//tft.getTouch( &touchX, &touchY, 600 );


    if( !touched )

    {

        data->state = LV_INDEV_STATE_REL;

    }

    else

    {

        data->state = LV_INDEV_STATE_PR;


        /*Set the coordinates*/

        data->point.x = touchX;

        data->point.y = touchY;


        Serial.print( "Data x " );

        Serial.println( touchX );


        Serial.print( "Data y " );

        Serial.println( touchY );

    }

}


void setup()

{

    Serial.begin( 115200 ); /* prepare for possible serial debug */


    String LVGL_Arduino = "Hello Arduino! ";

    LVGL_Arduino += String('V') + lv_version_major() + "." + lv_version_minor() + "." + lv_version_patch();


    Serial.println( LVGL_Arduino );

    Serial.println( "I am LVGL_Arduino" );


    lv_init();


#if LV_USE_LOG != 0

    lv_log_register_print_cb( my_print ); /* register print function for debugging */


    tft.begin();          /* TFT init */

    tft.setRotation( 3 ); /* Landscape orientation, flipped */


    lv_disp_draw_buf_init( &draw_buf, buf, NULL, screenWidth * screenHeight / 10 );


    /*Initialize the display*/

    static lv_disp_drv_t disp_drv;

    lv_disp_drv_init( &disp_drv );

    /*Change the following line to your display resolution*/

    disp_drv.hor_res = screenWidth;

    disp_drv.ver_res = screenHeight;

    disp_drv.flush_cb = my_disp_flush;

    disp_drv.draw_buf = &draw_buf;

    lv_disp_drv_register( &disp_drv );


    /*Initialize the (dummy) input device driver*/

    static lv_indev_drv_t indev_drv;

    lv_indev_drv_init( &indev_drv );

    indev_drv.type = LV_INDEV_TYPE_POINTER;

    indev_drv.read_cb = my_touchpad_read;

    lv_indev_drv_register( &indev_drv );



    ui_init();


    Serial.println( "Setup done" );

}


void loop()

{


    int rpm_value=map(analogRead(12),0,4095,0,250);

    uilabel_set_property(ui_Speed_Number_1, UILABEL_PROPERTY_TEXT, String(rpm_value).c_str());

    uilabel_set_property(ui_Speed_Number_2, UILABEL_PROPERTY_TEXT, String(rpm_value).c_str());

    lv_slider_set_value(ui_Slider_Speed, rpm_value,LV_ANIM_ON);



    int Bat_value=map(analogRead(14),0,4095,0,100);

    uilabel_set_property(ui_Label_Battery_Number, UILABEL_PROPERTY_TEXT, String(Bat_value).c_str());

    lv_slider_set_value(ui_Slider_Battery, Bat_value,LV_ANIM_ON);


    lv_timer_handler(); /* let the GUI do its work */

    delay(5);

}

######################################################################



Final Steps

  1. Upload the code to your ESP32 using the Arduino IDE.

  2. Open the Serial Monitor to check for any debug messages.

  3. Interact with the touchscreen to see your UI in action!


Tips

  • Adjust the pin assignments based on your wiring.

  • Explore LVGL's extensive documentation for more UI elements and functionalities.

  • Use LVGL's built-in tools to design and customize your interfaces.

This should give you a solid start on using LVGL with an ESP32 and a TFT LCD touchscreen. Happy coding!


Demo:


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