Flipping X and Y Axes in evdev

em_my · May 7, 2021, 2:39pm

lvgl/lv_drivers/blob/5466069db78de984f8a38abe40efe34e3de7a1a1/lv_drv_conf_template.h#L399


#  define USE_EVDEV           0
#endif

#ifndef USE_BSD_EVDEV
#  define USE_BSD_EVDEV       0
#endif

#if USE_EVDEV || USE_BSD_EVDEV
#  define EVDEV_NAME   "/dev/input/event0"        /*You can use the "evtest" Linux tool to get the list of devices and test them*/
#  define EVDEV_SWAP_AXES         0               /*Swap the x and y axes of the touchscreen*/

#  define EVDEV_CALIBRATE         0               /*Scale and offset the touchscreen coordinates by using maximum and minimum values for each axis*/

#  if EVDEV_CALIBRATE
#    define EVDEV_HOR_MIN         0               /*to invert axis swap EVDEV_XXX_MIN by EVDEV_XXX_MAX*/
#    define EVDEV_HOR_MAX      4096               /*"evtest" Linux tool can help to get the correct calibraion values>*/
#    define EVDEV_VER_MIN         0
#    define EVDEV_VER_MAX      4096
#  endif  /*EVDEV_CALIBRATE*/
#endif  /*USE_EVDEV*/

#define EVDEV_FLIP_AXE_Y 0
#define EVDEV_FLIP_AXE_X 0

github.com

lvgl/lv_drivers/blob/5466069db78de984f8a38abe40efe34e3de7a1a1/indev/evdev.c#L232


    data->state = evdev_button;

    if(data->point.x < 0)
      data->point.x = 0;
    if(data->point.y < 0)
      data->point.y = 0;
    if(data->point.x >= drv->disp->driver.hor_res)
      data->point.x = drv->disp->driver.hor_res - 1;
    if(data->point.y >= drv->disp->driver.ver_res)
      data->point.y = drv->disp->driver.ver_res - 1;

    return false;
}

/**********************
 *   STATIC FUNCTIONS
 **********************/
int map(int x, int in_min, int in_max, int out_min, int out_max)
{
  return (x - in_min) * (out_max - out_min) / (in_max - in_min) + out_min;
}

#if EVDEV_FLIP_AXE_X
data->point.x = drv->disp->driver.hor_res - data->point.x;
#endif

#if EVDEV_FLIP_AXE_Y
data->point.y = drv->disp->driver.ver_res - data->point.y;
#endif

kisvegabor · May 10, 2021, 8:19am

Hi,

/*to invert axis swap EVDEV_XXX_MIN by EVDEV_XXX_MAX*/

As the comment says you can swap MIN and MAX to flip the axis.