Custom fonts crashing the board (platformIO/ESP32)

How-to
1

What do you want to achieve?

Using custom fonts with LVGL without crashing.

What have you tried so far?

I have used the online font converter to generate a custom font with only printable ASCII char for testing. I have declared the font in lv_conf.h and used in my main.cpp, the build & upload have no problem, but the board seems entered a crash loop once I started to use the font to display something. When I switch back to built-in font, the text shown with no problem.

The font, named lv_font_test_16.c, is placed in \.pio\libdeps\my_env\lvgl\src\font
(the docs just said “copy into your LGVL project”, which is pretty confusing to me.)

P.S., I am very new to LVGL

Code to reproduce

Code of declaring the font in lv_conf.h (line 629):

#define LV_FONT_CUSTOM_DECLARE LV_FONT_DECLARE(lv_font_test_16)

Code of using the font in style, main.cpp:

 lv_style_init(&CJK_font);
 lv_style_set_text_font(&CJK_font, &lv_font_test_16);

Note that it was working well when using built-in font, so I don’t think the problem is in main.cpp

Parameter in the font converter:

name: lv_font_test_16
size: 16
Bpp: 2bit/px
fallback: lv_font_test_16
output format: C file

Enabled Font compression
Font range: 0x20-0x7F (printable ASCII char)

Size: 33KB

Environment

PlatformIO / VScode

  • MCU/MPU/Board: ESP32S3 with ST7789 2.8inch LCD TFT display
  • LVGL version:: 9.3.0
2

Hi

I would not put the font in that folder, the font file you can put it in the src folder, where all your c files code is. The folder you used is “internal” to PlatformIo and it will typically not be placed under version control (to share code with other persons / computer) and i think is “cleared” when you performa a “clean build”.

You can keep the #define LV_FONT_CUSTOM_DECLARE LV_FONT_DECLARE(lv_font_test_16) I think is OK, I normally just add in one of my files:

LV_FONT_DECLARE(myfont_18)

typically, on main.c or in the gui.c file… in order to use it in the rest of the code.

Eventually attach the generated font file, to check for issues.

3

Nope, it’s still crashing
Ima attach the font here:
lv_font_test_16.c (32.0 KB)

and here is the main.cpp as i can’t upload C++ files:

#include <Arduino.h>
#include <lvgl.h>
#include <TFT_eSPI.h>

#define BUF_SIZE (320 * 240 / 10) // Reduced buffer size

TFT_eSPI tft = TFT_eSPI();

static lv_style_t CJK_font;

lv_obj_t *player_lable;
lv_obj_t *title_lable;
lv_obj_t *artist_lable;

static uint8_t buf1[BUF_SIZE];
static uint8_t buf2[BUF_SIZE];

String receivedMessage[6] = {"", "", ""};
String values[6] = {"", "", ""};

int counter = 0;

/* Tick source, tell LVGL how much time (milliseconds) has passed */
static uint32_t get_time(void)
{
    return millis(); // Use millis() for Arduino compatibility
}

/* Display flushing */
void my_disp_flush(lv_display_t *disp, const lv_area_t *area, uint8_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[0], w * h, true);
    tft.endWrite();

    lv_display_flush_ready(disp);
}

void setup() {
  Serial.begin(115200); // Initialize hardware serial for USB communication
  pinMode(2, OUTPUT);
  analogWrite(2, 100);             // Backlight PWM

  lv_init();

  // TFT init
  tft.init();
  tft.setRotation(1); // Adjust rotation as needed
  tft.fillScreen(TFT_BLACK);

  lv_tick_set_cb(get_time);

  lv_display_t * display1 = lv_display_create(320, 240);

  lv_display_set_buffers(display1, buf1, buf2, BUF_SIZE, LV_DISPLAY_RENDER_MODE_PARTIAL);

  lv_display_set_flush_cb(display1, my_disp_flush);

  LV_FONT_DECLARE(lv_font_test_16);
  lv_style_init(&CJK_font);
  lv_style_set_text_font(&CJK_font, &lv_font_test_16);

  //[Player_Name]
  player_lable = lv_label_create(lv_scr_act());
  lv_label_set_text(player_lable, "Stopped");
  lv_obj_align(player_lable, LV_ALIGN_TOP_LEFT, 10, 10);

  //[Title]
  title_lable = lv_label_create(lv_scr_act());
  lv_label_set_text(title_lable, "Fetching");
  lv_obj_align(title_lable, LV_ALIGN_TOP_LEFT, 10, 30);
  lv_obj_add_style(title_lable, &CJK_font, 0);

  //[Artist]
  artist_lable = lv_label_create(lv_scr_act());
  lv_label_set_text(artist_lable, "Fetching");
  lv_obj_align(artist_lable, LV_ALIGN_TOP_LEFT, 10, 50);
  lv_obj_add_style(artist_lable, &CJK_font, 0);


  while (Serial.available()){
    Serial.read();
  }
}

void loop() {
  while (Serial.available()) { // Check if data is available in the Serial buffer

    char incomingChar = Serial.read(); // Read each character

    if (incomingChar == '\n') { // If newline character (Enter) is received
      receivedMessage[counter] += '\n';
      counter++;

      if (counter >= 6){
        counter = 0;
        for (int i = 0; i < 6; i++){
          values[i] = receivedMessage[i];
          receivedMessage[i] = "";
        }
      }

    } else {
      receivedMessage[counter] += incomingChar; // Append characters to the message
    }
  }
  lv_label_set_text(player_lable, values[0].c_str());
  lv_label_set_text(title_lable, values[1].c_str());
  lv_label_set_text(artist_lable, values[2].c_str());
  lv_timer_handler(); // Update the UI
  delay(5);
}

Tho im planning to give up on custom font, as I noticed I need to make multiple font files for different font size, and i wanna use CJK fonts, which means most likely i will be short on memory.

4

Sorry, don’t see any obvious issue, it seems to work on the simulator.

One thing i would do, is to pass the font decaration:

LV_FONT_DECLARE(lv_font_test_16);

to the start of the c file, like, next to the

static lv_style_t CJK_font;

Although on the simulator, there was no “issue” with doing that, but since that macro extends to extern const lv_font_t font_name; is better to have it outside functions or in a h file…

And when the ESP Crash… what is it complaining? what does it print on the serial console? It typically tells the function/line where the crash was created…

5

Too cleaner is place lv_timer_handler(); // Update the UI on loop start.