Linux Framebuffer problem on Raspberry PI

General discussion
1

So, I have upgraded to 8 and I am having an issue getting the framebuffer driver initialized and working.
As a test I wrote to /dev/fb0 and got data on the screen, so the actual device is working.

Here is my intialization:
lv_init();
fbdev_init();
/Initialize a descriptor for the buffer/
lv_disp_draw_buf_init(&disp_buf, buf, NULL, DISP_BUF_SIZE);

/*Initialize and register a display driver*/
static lv_disp_drv_t disp_drv;
lv_disp_drv_init(&disp_drv);
disp_drv.draw_buf   = &disp_buf;
disp_drv.flush_cb   = fbdev_flush;
disp_drv.hor_res    = 800;
disp_drv.ver_res    = 480;
lv_disp_drv_register(&disp_drv);
lv_theme_default_init(NULL, lv_palette_main(LV_PALETTE_BLUE), lv_palette_main(LV_PALETTE_RED), LV_THEME_DEFAULT_DARK, LV_FONT_DEFAULT);

I end up with nothing displaying on the screen. Im at a bit of a loss.

2

Disregard for now, seems I had a weird hybrid of v7 and v8

3

Sadly that was not it. Still same thing, I do all the init, create a window but it doesnt appear on the screen.

4

I can’t think of anything off the top of my head. The usual mistake is to not make disp_drv static but you did that already. Perhaps try enabling logging and asserts; hopefully it will give a clue as to what the problem is.

5

Ill do so and report back what I find

6

Ditto,
My code below is similar to yours and it is working on Raspberry Pi.

deon@pi4-lcd7c:~ $ uname -a
Linux pi4-lcd7c 5.10.63-v7l+ #1496 SMP Wed Dec 1 15:58:56 GMT 2021 armv7l GNU/Linux

#include "lvgl/lvgl.h"
#include "lv_drivers/display/fbdev.h"
#include "lv_drivers/indev/evdev.h"
#include "lv_demos/lv_demo.h"
#include <unistd.h>
#include <pthread.h>
#include <time.h>
#include <sys/time.h>

#define DISP_BUF_SIZE (128 * 1024)

static void hal_init(void);
static void every100ms(void);

int main(void)
{
    /*LVGL init*/
    lv_init();

    hal_init();

    /*Create a Demo*/
    lv_demo_widgets();

    /*Handle LVGL tasks (tickless mode)*/
    while( 1 ) {
        lv_task_handler();
        usleep( 5000 );
        static uint16_t ctr;
        if( ++ctr >= 1000000/5000/10 ) {
            ctr = 0;
            every100ms();
        }
    }

    return 0;
}

/*Set in lv_conf.h as `LV_TICK_CUSTOM_SYS_TIME_EXPR`*/
uint32_t app_custom_tick_get ( void )
{
    static uint64_t start_ms = 0;
    if( start_ms == 0 ) {
        struct timeval tv_start;
        gettimeofday( &tv_start, NULL );
        start_ms = (tv_start.tv_sec * 1000000 + tv_start.tv_usec) / 1000;
    }

    struct timeval tv_now;
    gettimeofday( &tv_now, NULL );
    uint64_t now_ms;
    now_ms = (tv_now.tv_sec * 1000000 + tv_now.tv_usec) / 1000;

    uint32_t time_ms = now_ms - start_ms;
    return time_ms;
}

#include <stdio.h>
#include <stdlib.h>

static bool backlightOn;
static uint16_t backlightOnTmr;

static bool BacklightOn ( void )
{
    if( backlightOn ) return true;
    backlightOn    = true;
    backlightOnTmr = 600;
    system( "/home/deon/backlight-on.sh" );
    printf( "Backlight On\n" );
    return true;
}

static bool BacklightOff ( void )
{
    if( !backlightOn ) return false;
    backlightOn = false;
    system( "/home/deon/backlight-off.sh" );
    printf( "Backlight Off\n" );
    return false;
}

static void every100ms(void)
{
    if( backlightOnTmr )
        if( !--backlightOnTmr )
            BacklightOff();
}

static void _evdev_read ( lv_indev_drv_t *drv, lv_indev_data_t *data )
{
    evdev_read( drv, data );

    if( data->state == LV_INDEV_STATE_PRESSED ) {
        if(!backlightOn)
            BacklightOn();
        else
            backlightOnTmr = 600;
    }
}

void hal_init(void)
{
    /*Linux frame buffer device init*/
    fbdev_init();

    /*A small buffer for LVGL to draw the screen's content*/
    static lv_color_t buf[ DISP_BUF_SIZE ];

    /*Initialize a descriptor for the buffer*/
    static lv_disp_draw_buf_t disp_buf;
    lv_disp_draw_buf_init( &disp_buf, buf, NULL, DISP_BUF_SIZE );

    /*Initialize and register a display driver*/
    static lv_disp_drv_t disp_drv;
    lv_disp_drv_init( &disp_drv );
    disp_drv.draw_buf = &disp_buf;
    disp_drv.flush_cb = fbdev_flush;
    disp_drv.hor_res  = 800;
    disp_drv.ver_res  = 480;
    lv_disp_drv_register( &disp_drv );
    lv_theme_default_init(NULL, lv_palette_main(LV_PALETTE_BLUE), lv_palette_main(LV_PALETTE_RED),
        LV_THEME_DEFAULT_DARK, LV_FONT_DEFAULT);
#if USE_EVDEV
    BacklightOn();
    evdev_init();
    static lv_indev_drv_t indev_drv_touch;
    lv_indev_drv_init( &indev_drv_touch );
    indev_drv_touch.type    = LV_INDEV_TYPE_POINTER;
    indev_drv_touch.read_cb = _evdev_read;
    lv_indev_drv_register( &indev_drv_touch );
#endif
}
1 Like
7

Do I have to admit my stupidity?

I wasnt calling task handler…

8

Been there, done that :rofl:

9

So annoying, but so norrmal, big project, lots of moving parts doing lots of cool things…

Forget something simple.