8 bit "Mcufriend" shield and LVGL

[mltongca]

Following your instructions to set up 8 bit "Mcufriend" shield on ESP32 UNO style board with a resistance based touch screen, the display and the touch screen work very well. Is it possible to for this display and touch screen to work with LVGL? Thanks.

[Bodmer]

Yes, this will work but I do not have an example for that library. Consult the LVGL documentation.

[ckshum88]

Although it has been two years since the original poster started this thread, I append below for record an example of callback functions to use LVGL with 8-bit MCUFRIEND LCD shield.

// LCD and touch screen settings
MCUFRIEND_kbv tft;
// Touch screen wiring and calibration
#define MINPRESSURE 200
#define MAXPRESSURE 1000
const int XP=12,XM=15,YP=33,YM=13;    //modify as per pin configuration of the shield used
const int TS_LEFT=935,TS_RT=180,TS_TOP=72,TS_BOT=936;     //replace with your own calibration data
TouchScreen_kbv ts = TouchScreen_kbv(XP, YP, XM, YM, 300);

... 

/* LVGL calls it when a rendered image needs to copied to the display */
void my_disp_flush( lv_display_t *disp, const lv_area_t *area, uint8_t * px_map)
{
    /* Copy `px map` to the `area` */
    uint32_t size = lv_area_get_size(area);

    /* Set TFT address window to clipped image bounds */
    tft.setAddrWindow(area->x1, area->y1, area->x2, area->y2);
    tft.pushColors( (uint16_t *) px_map, size, true );
    tft.setAddrWindow(0, 0, tft.width() - 1, tft.height() - 1); //restore full screen

    /* Call it to tell LVGL you are ready */
    lv_display_flush_ready(disp);
}

/* Read the touchpad */
void my_touchpad_read( lv_indev_t * indev, lv_indev_data_t * data )
{
    int32_t x, y;

    TSPoint_kbv p = ts.getPoint();
    pinMode(YP, OUTPUT);      //restore shared pins
    pinMode(XM, OUTPUT);
    digitalWrite(YP, HIGH);   //because TFT control pins
    digitalWrite(XM, HIGH);
    x = map(p.x, TS_LEFT, TS_RT, 0, tft.width()); //.kbv makes sense to me
    y = map(p.y, TS_TOP, TS_BOT, 0, tft.height());

    bool touched = (p.z > MINPRESSURE && p.z < MAXPRESSURE);
    if(!touched) {
        data->state = LV_INDEV_STATE_RELEASED;
    } else {
        data->state = LV_INDEV_STATE_PRESSED;
        data->point.x = x;
        data->point.y = y;
    }
}

void setup()
{

...

    /*Create a display*/
    lv_display_t * disp = lv_display_create(TFT_HOR_RES, TFT_VER_RES);
    lv_display_set_flush_cb(disp, my_disp_flush);
    lv_display_set_buffers(disp, draw_buf, NULL, DRAW_BUF_SIZE/4, LV_DISPLAY_RENDER_MODE_PARTIAL);

    /*Initialize the input device driver*/
    lv_indev_t * indev = lv_indev_create();
    lv_indev_set_type(indev, LV_INDEV_TYPE_POINTER); /*Touchpad should have POINTER type*/
    lv_indev_set_read_cb(indev, my_touchpad_read);

 ...
}