How to init and toggle led properly?

How-to
1

hey there! i have problems with leds(actually its pointers)

i have an empty global pointers (for example below)

volatile lv_obj_t *led_pointer;

i have init function that looks like

void lv_init_led(lv_obj_t * ledobj,lv_obj_t* par,lv_coord_t x,lv_coord_t y,lv_coord_t sizex,lv_coord_t sizey,char* text_to_the_left,lv_coord_t text_Y_offset)
{
ledobj  = lv_led_create(par, NULL);
lv_obj_set_size(ledobj,sizex,sizey);
lv_obj_set_pos(ledobj,x,y);
lv_led_off(ledobj);
lv_obj_t * label1 = lv_label_create(par, NULL); 
lv_obj_align(label1,ledobj,LV_LABEL_ALIGN_LEFT,text_Y_offset,0);
}

it was made for fast init of bunch of leds.

init sequence works fine, and i can even toggle led in it (in function)
but outside of this function i cant toggle led - program crashes with null-pointer error

Error: lv_led_on        (lv_led.c #131 lv_led_on())
Error: NULL pointer (0x00000000)        (lv_debug.c #127 lv_debug_log_error())

but the same works with buttons and labels and other objects.
What i am douing wrong?

2

Check that you are not redeclaring the pointer inside the function (shadowing). In your example the global is called led_pointer but you’re assigning the result to ledobj.

3

it looks like that - also there is no shadowing warnings from gcc…

lv_obj_t* MeanTimesLabelBtn=NULL;
lv_obj_t* F_ABS_LABEL=NULL;
lv_obj_t* UDC_LABEL=NULL;
volatile lv_obj_t *led_1ghz;
volatile lv_obj_t *led_UHF_OK=NULL;
volatile lv_obj_t *led_220V_present=NULL;
volatile lv_obj_t *led_1ghz_out_enabled=NULL;



void createlabels(lv_obj_t* par)
{
createstyledbutton(MeanTimesLabelBtn,par,labelbtnstyle_pointer,10,10,BUTTON_WIDTH,BUTTON_HEIGHT,"MEAN TIMES",dummybtn_cb);
createstyledbutton(F_ABS_LABEL,par,labelbtnstyle_pointer,10,160,BUTTON_WIDTH,BUTTON_HEIGHT,"F_ABS",dummybtn_cb);
createstyledbutton(UDC_LABEL,par,labelbtnstyle_pointer,10,235,BUTTON_WIDTH,BUTTON_HEIGHT,"Udc",dummybtn_cb);
lv_init_led(led_1ghz,par,460,315,40,40,"1 GHz",-50);
lv_init_led(led_UHF_OK,par,460,DEFLEDY+55*1,40,40,"UHF",-45);
lv_init_led(led_220V_present,par,460,DEFLEDY+55*2,40,40,"220V",-50);
lv_init_led(led_1ghz_out_enabled,par,460,DEFLEDY+55*3,40,40,"1 GHz out",-90);
}
4 
lv_obj_t * createstyledbutton(lv_obj_t * btn,lv_obj_t * par,lv_style_t* style, lv_coord_t pos_x,lv_coord_t pos_y,lv_coord_t size_wide,lv_coord_t size_height,char btn_text[],lv_event_cb_t event_call_back_function)
{
btn = lv_btn_create(par, NULL);     /*Add a button the current screen*/
lv_obj_add_style( btn, LV_OBJ_PART_MAIN,style);
lv_obj_align(btn, NULL, LV_ALIGN_CENTER, 0, 0);
lv_obj_set_pos(btn,  pos_x,  pos_y);                            /*Set its position*/
lv_obj_set_size(btn,size_wide, size_height);                          /*Set its size*/
lv_obj_set_event_cb(btn, event_call_back_function);                 /*Assign a callback to the button*/
lv_obj_t * label = lv_label_create(btn, NULL);          /*Add a label to the button*/
lv_label_set_text(label, btn_text);                     /*Set the labels text*/
return label;
}

actually for labels in buttons that i need to change - i am using return value. my daywork ended
i will try to return pointer to global pointer of led tomorrow.

5

That’s your problem. You are just reassigning the argument passed to the function. This doesn’t change the value outside of the function.

6

but i am sending argument as a pointer - not as just input value?! in my example i am creating label in function - this may cause problems if i dont save that pointer. but for leds - there are global pointers… cant understand…

7

ive changed function. seems works well. inside function there is lv_obj_t* led_obj = lv_led_create(par, NULL);

lv_obj_t* lv_init_led(lv_obj_t* par,lv_coord_t x,lv_coord_t y,lv_coord_t sizex,lv_coord_t sizey,char* text_to_the_left,lv_coord_t text_Y_offset);
and it returns pointer on exit.
But i cant understand why it is so…