Keyboard callback is not navigating in menus

How-to
1

Description

keyboard callback is not navigating in menus

What MCU/Processor/Board and compiler are you using?

Atmel Cortex M7 MCU, Atmel Studio, GCC

What LVGL version are you using?

7.7.2

What do you want to achieve?

With the serial port receive, I like to navigate by receiving on the serial port the + and - characters

What have you tried so far?

I put a breakpoint in my code. It properly breaks when I receive a serial characters. I see no navigation happening in my LCD GUI. I already made the touchscreen and rotary encoder navigate properly.

I don’t understand when I am supposed to return true or false in the callback.

Code to reproduce

bool isKeyPressed=false;
char serialReadBuffer[1]={0};
	
void serial_rx_cb(const struct usart_async_descriptor * const io_descriptor ){
	isKeyPressed=true;
	int32_t status =0;
	status = io_read(ioSerial, (  uint8_t *)serialReadBuffer, 1 )  ;
}



bool my_keyboard_read(lv_indev_drv_t * drv, lv_indev_data_t*data){
	 
	int32_t status =0;
	
	if  (isKeyPressed==true){
		  
		if (serialReadBuffer[0]=='5') data->key = LV_KEY_ENTER;
		else if (serialReadBuffer[0]=='+') data->key = LV_KEY_NEXT;
		else if (serialReadBuffer[0]=='-') data->key = LV_KEY_PREV;
		else if (serialReadBuffer[0]=='8') data->key = LV_KEY_UP;
		else if (serialReadBuffer[0]=='4') data->key = LV_KEY_LEFT;
		else if (serialReadBuffer[0]=='6') data->key = LV_KEY_RIGHT;
		else if (serialReadBuffer[0]=='2') data->key = LV_KEY_DOWN;
		else data->key = LV_KEY_NEXT;
		
		data->state = LV_INDEV_STATE_PR;  
		isKeyPressed=false; /*breakpoint here*/
	}else {
		data->state = LV_INDEV_STATE_REL;
	}

	return false; /*I don't understand what I am supposed to return*/
}


lv_indev_t * enc_indev_3 ;
lv_indev_drv_t indev_drv3;
void init(void){
 	lv_indev_drv_init(&indev_drv3);
 	indev_drv3.type = LV_INDEV_TYPE_KEYPAD;
 	indev_drv3.read_cb = my_keyboard_read;
 	enc_indev_3 =  lv_indev_drv_register(&indev_drv3);

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