I ran the scrolling example, but the screen seemed to have a residual image and refresh slowly

[ShiPC123]

I used STM32F103RCT6 and F411 microcontroller, the display effect is the same

video.3.mp4

Here is my test code
void loop(void)
{

// create foreground colors
uint16_t col[] = {
    dmd.Color888(255,0, 0), // red

};
uint16_t bg = 0;  // background - black
int col_cnt = 3;   // color count

// text
char s[] = "hello 1122334455";
// transcode message to UTF for use with GFX fonts
char k[30];

utf8_rus(k, (const unsigned char*)s);
char* m = s;
// select standard font
dmd.selectFont(&UkrRusArial_F);

// set text foreground and background colors
dmd.setTextColor(col[0], bg);

// shift steps in pixels for running text (positive - shift right, negative - left)
int8_t step[] = { -1,-1,-1,-1 };
// running text shift interval
uint16_t interval = 10;

long prev_step = millis();
uint8_t col_ptr = 0;
uint8_t i = 0, b = 0;
uint8_t test = 255;
uint8_t test_cnt = 4;
dmd.setBrightness(100);
int x=dmd.width() - 1;
while (1) {
    if ((millis() - prev_step) > interval) {
      prev_step = millis();  // moved to the start of the loop to prevent "scroll not smooth" issue
      x--;
      if(x<-1*dmd.stringWidth(m))
      {
        x= dmd.width() - 1;
      }

    }
      dmd.drawMarqueeX(m, x, 12);
      dmd.swapBuffers(true);
    
}

}

[ShiPC123]

1.mp4

[board707]

Hi
Could you clarify an issue? I didn't catch the problem from the video.

[ShiPC123]

Hello, maybe can't see the effect from the inside of the camera, but to the naked eye, can see how Carton feels. The rolling is not smooth

[ShiPC123]

How can I improve the flow of the roll

[board707]

Honesty, I don't see any distortions :)
I have try it at home.

By anyway, try to increase a scrolling interval:
uint16_t interval = 10;
The 10 mS is probably too tight for the task.

[ShiPC123]

Thanks, I will try to re-shoot the video tomorrow, and I feel that the shadow will appear when I scroll

[ShiPC123]

Is there any relevant document that can explain the function, such as dmd.drawMarqueeX? I wonder if I didn't clear the screen or didn't call some functions, which caused the scrolling to have residual shadows

[board707]

Read the library Wiki
The brief explanation of the functions: DMD_STM32 Reference