Issue with touchpad of Stm32f429 Discovery board

How-to
1

Hello all,
Recently, I ported LVGL ver9.0.0 to the STM32f429Discovery kit. I ran the "lv_example_calendar_1() " and noticed the touch is not calibrated. Because when I clicked on a place out of the calendar box specific day highlighted it. In the following picture, you can see I did click on the top right and day 30 is highlighted. I am using STM32CubeIDE as well.
Also, I have two warnings also:

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2
  1. I think you need to flip touch vertically.
  2. about warnings. Can you show code in this lines?
3

One error is due to the function touchpad_read, as it returns bool, while callback doesn’t accept any return type.
I fixed this by changing the return type to void, because I don’t see if return value has some usage, as it is always returning false.
For GCC compiler this is not a problem, as it just generates warning, but when I ported the same code for IAR compiler, I received 100 of warnings and for this piece of code I received error (which without fixing this I can’t even compile).
Out of context when I ported my code from STM32CubeIDE to IAR, it doesn’t work and I get Hard-Fault error, more information here, but with STM32CubeIDE everything works well
Hard Fault Error when executing the function lv_timer_handler - Get started - LVGL Forum

4

Hello spider_vc,
How to flip the touch vertically?
Here is related to touch:

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The following related to the warning for memset :slight_smile:
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5

The 'F429 Disco is manufactured for almost a decade an during that time it came in several variants, some of them have touchscreen flipped, some not.

https://community.st.com/s/question/0D73W000001NTvzSAG/detail?s1oid=00Db0000000YtG6&t=1643412206102&s1nid=0DB0X000000DYbd&emkind=chatterCommentNotification&s1uid=0050X000007vsKk&emtm=1643407322266&fromEmail=1&s1ext=0

https://www.eevblog.com/forum/microcontrollers/need-hex-file-to-test-touch-screen-on-stm32f429-discovery-board/

JW

6

For future case don’t post screen shot instead use CODE format.
change you touchpad_read function declaration to:

static void touchpad_read(lv_indev_drv_t * drv, lv_indev_data_t *data)
{
.....
}

second. How is my_fb declared?

and finally. when reading X/Y coords from touchscreen make flip of Y coordinate.

y = TFT_VER_RES - y;
7

Hello spider_vc
Thank you for your information. I will put the code instead of a screenshot in the future.
By flipping the Y coordinate it did work. Thank you very much for your valuable information.
you asked about my_fb declaration, it declares as below, I did not change its declaration:
#if TFT_EXT_FB != 0
SDRAM_HandleTypeDef hsdram;
FMC_SDRAM_TimingTypeDef SDRAM_Timing;
FMC_SDRAM_CommandTypeDef command;
static __IO uint16_t * my_fb = (__IO uint16_t*) (SDRAM_BANK_ADDR);
#else
static uint16_t my_fb[TFT_HOR_RES * TFT_VER_RES];
#endif

I am not using external buffer so I disabled it via TFT_EXT_FB in the “tft.h” file I copied as the follow:
#define TFT_EXT_FB 0
So the my_fb is declared like this:
static uint16_t my_fb[TFT_HOR_RES * TFT_VER_RES];

8

thi simples way to fix warning is :

memset(my_fb, 0x1234, sizeof(my_fb));

but it will work only for TFT_EXT_FB == 0
else and universal way is:

memset(my_fb, 0x1234, sizeof(my_fb[0])*TFT_HOR_RES * TFT_VER_RES);
9

Hello spider_vc
Sorry for the late reply. Now all are Ok and working with no errors and no warnings. Thank you very much for your information and help!

1 Like
10

hi spider, would please expand on the solution, i have this problem and i followed your instruction in the touchpad.c file i commented all the content of touchpad_read function but compiler threw an error about this function thank you in advance

11

hi guys, i have same issue with my touchpad because it is not accurate.this is my model MB1075-F429I-E01.