How to use CST816S with lvgl for gestures

How-to
1

Description

How can I use the CST816S touch driver with lvgl to detect gestures like scrolling and swiping?

What MCU/Processor/Board and compiler are you using?

ESP32 WROOM-32

What LVGL version are you using?

LVGL Version 8.3.4

What do you want to achieve?

Swipe and Scroll Gestures for CST816S

What have you tried so far?

I have tried detecting the gesture and direction of the gesture but it is always 0 since lvgl uses TFT_eSPI for touch controls but I am using the CST816S driver which is not detected.
How can I use the CST816S library to detect gestures such as swiping and scrolling? I am also using a GC9A01 LCD display. The click and Long press are working perfectly. Thanks, I am a newbie at this and have no clue how I can integrate them together.

2

I’m also working on a project with GC9A01 display with pio and Arduino framework
Here is my experience:
Include “CST816S.h”
Initialize Class CST816S like this:
CST816S mytouch(sda,scl,rst,irq);(here is your i2c attached pin numbers)
Then tell lvgl to read i2c input:
void touchpad_read(lv_indev_drv_t * indev_drv, lv_indev_data_t * data)
{
last_x = 0;
last_y = 0;
if(mytouch.available()) {
last_x = mytouch.data.x;
last_y = mytouch.data.y;
data->state = LV_INDEV_STATE_PR;
}
else {
data->state = LV_INDEV_STATE_REL;
}
data->point.x = last_x;
data->point.y = last_y;
}
Next, register callback:
void lv_port_indev_init(void)
{
static lv_indev_drv_t indev_drv;

/*Register a touchpad input device*/
lv_indev_drv_init(&indev_drv);
indev_drv.type = LV_INDEV_TYPE_POINTER;
indev_drv.read_cb = touchpad_read;
indev_touchpad = lv_indev_drv_register(&indev_drv);

}

In my project,after doing this, lvgl can read my gesture input.
Hope my advice works!

3

Thanks. It worked I forgot to put the two lines in the function:

data->point.x = last_x;
data->point.y = last_y;

Thanks for helping

4

Edit: It looks like this void type is probably due to me not using an ESP I guess?

I’m using a pico trying to accomplish the same thing. Are you using the Arduino <CST816S.h> or a custom?
What are you setting the touch cs to?

I get all sorts of kickback when trying to implement your approach with the Arduino library version.
In file included from C:\Users\wimbe\Desktop\LVGL_Arduino\LVGL_Arduino.ino:6:

CST816S.h:74:10: error: variable or field ‘IRAM_ATTR’ declared void
74 | void IRAM_ATTR handleISR();
| ^~~~~~~~~
CST816S.h:74:10: error: expected ‘;’ at end of member declaration
74 | void IRAM_ATTR handleISR();
| ^~~~~~~~~
| ;
CST816S.h:74:20: error: ISO C++ forbids declaration of ‘handleISR’ with no type [-fpermissive]
74 | void IRAM_ATTR handleISR();
| ^~~~~~~~~
LVGL_Arduino.ino: In function ‘void lv_port_indev_init()’:
LVGL_Arduino:64:3: error: ‘indev_touchpad’ was not declared in this scope
64 | indev_touchpad = lv_indev_drv_register(&indev_drv);
| ^~~~~~~~~~~~~~
LVGL_Arduino.ino: In function ‘void my_touchpad_read(lv_indev_drv_t*, lv_indev_data_t*)’:
LVGL_Arduino:86:22: error: ‘class TFT_eSPI’ has no member named ‘getTouch’
86 | bool touched = tft.getTouch( &touchX, &touchY, 600 );
| ^~~~~~~~
LVGL_Arduino.ino: In function ‘void setup()’:
LVGL_Arduino:131:7: error: ‘class TFT_eSPI’ has no member named ‘setTouch’
131 | tft.setTouch( calData );
| ^~~~~~~~
exit status 1
‘indev_touchpad’ was not declared in this scope

5

Did you declare the User setup for TFT_eSPI? It seems like it’s not able to find the method declarations for getTouch and such but I might be wrong. I had a similar problem when I forgot to declare my pins and drivers for TFT_eSPI.

1 Like
6

Sorry, Yea in this screenshot I did not because I was troubleshooting the top error.