Linux Evdev Driver
Overview
The Linux event device (evdev) is a hardware-independent API that gives access to input events from, for example, a mouse or touchscreen. It is exposed via the Linux device file system interface.
Prerequisites
Your system has an input device configured (usually under /dev/input/
such as /dev/input/event0
).
Configuring the driver
Enable the Linux LVGL evdev driver support in lv_conf.h
.
#define LV_USE_EVDEV 1
Usage
To set up an event input, first create an input device with lv_edev_create
setting it to the correct Linux event device.
Then link this to the LVGL display with lv_indev_set_display
.
lv_indev_t *touch = lv_evdev_create(LV_INDEV_TYPE_POINTER, "/dev/input/event0");
lv_indev_set_display(touch, disp);
Ensure that an lv_display_t
object is already created for disp
. An example for this is shown below, using the Linux framebuffer driver.
lv_display_t * disp = lv_linux_fbdev
lv_linux_fbdev_set_file(disp, "/dev/fb0");_create();
Locating your input device
If you can't determine your input device, first run
`$cat /proc/bus/input/devices`
This should show input devices and there will be entries with the word event
which give a clue as to the device to use eg. event1
would be /dev/input/event1
.
You can use evtest
to show data from that event source to see if it is actually the one you want.
Try:
$evtest /dev/input/event1
replacing eventX
with your event device from above.
Automatic input device discovery
There is support for automatically finding and adding input devices in /dev/input/
. New devices will automatically be added
when they are connected. To enable this feature, you can simply call lv_evdev_discovery_start(NULL, NULL).
You may want to react to a new device being added so that a cursor image can be applied, for example. You can provide a callback function which will be called when a new device is added.
#include "lvgl/src/core/lv_global.h"
static void indev_deleted_cb(lv_event_t * e)
{
if(LV_GLOBAL_DEFAULT()->deinit_in_progress) return;
lv_obj_t * cursor_obj = lv_event_get_user_data(e)
lv_obj_delete(cursor_obj);
}
static void discovery_cb(lv_indev_t * indev, lv_evdev_type_t type, void * user_data)
{
LV_LOG_USER("new '%s' device discovered", type == LV_EVDEV_TYPE_REL ? "REL" :
type == LV_EVDEV_TYPE_ABS ? "ABS" :
type == LV_EVDEV_TYPE_KEY ? "KEY" :
"unknown");
if(type == LV_EVDEV_TYPE_REL) {
LV_IMAGE_DECLARE(mouse_cursor_icon);
lv_obj_t * cursor_obj = lv_image_create(lv_screen_active());
lv_image_set_src(cursor_obj, &mouse_cursor_icon);
lv_indev_set_cursor(indev, cursor_obj);
lv_indev_add_event_cb(indev, indev_deleted_cb, LV_EVENT_DELETE, cursor_obj);
}
}
int main()
{
/* ... */
lv_evdev_discovery_start(discovery_cb, NULL);
/* ... */
}
At the time of writing, this feature is not supported in BSD. .. Autogenerated