#include "stm32l031xx.h"

#define GPIOBEN							(1U<<1)					// ENABLES GPIOB  SHIFT 1 to POSITION 1`  
#define PIN3								(1U<<3)				  // ENABLES PIN3
#define LED_PIN							 PIN3						// USER_LED_PIN is connected to PB3

#define GPIOAEN							(1U<<0)					// ENABLES GPIOA	SHIFT 1 to POSITION 0
#define PIN11								(1U<<11)				// ENABLES PIN11
#define USER_BUTTON				   PIN11					// USER_BUTTON is connected to PA11

int main()
{

	RCC->IOPENR			 |= 			GPIOAEN;				/* 1.1 :  ENABLES  CLK access to GPIOA  from I/o peripheral address */
	RCC->IOPENR			 |= 			GPIOBEN;				/* 1.2 :  ENABLES  CLK access to GPIOB from I/o peripheral address */

	/*MODER 01 FOR OUTPUT */

	GPIOB->MODER 		 |= 			(1U<<6);				/* 2.1 :	SET GPIOB  as O/P using MODER  register 6 PIN 1 */
	GPIOB->MODER 		 &=		   ~(1U<<7);			  /* 2.2 :	SET GPIOB  as O/P using MODER  register 7 PIN 0 */

	/*MODER 00 FOR INPUT */
	GPIOA->MODER 		 &=		  ~(1U<<23);				/* 2.3 :	SET GPIOB  as I/P using MODER  register 23 PIN 0 */
	GPIOA->MODER 		 &=		  ~(1U<<22);			  /* 2.4 :	SET GPIOB  as I/P using MODER  register 22 PIN 0 */

	/*PUPDR 01 FOR PULLUP */
	GPIOA->PUPDR 		 &=		  ~(1U<<23);				/* 2.5 :	SET GPIOB  as I/P using PUPDR  register 23 PIN 0 */
	GPIOA->PUPDR 		 |=		   (1U<<22);			  /* 2.6 :	SET GPIOB  as I/P using PUPDR  register 22 PIN 1 */

	while(2){

		/*Check if BUTTON is pressed */
		if (GPIOA->IDR  & USER_BUTTON){
			GPIOB->BSRR |= (1U<<19);		          // RESET PIN3 i.e enable reset pin 19 or turn ON LED
		}
		else {
		  GPIOB->BSRR  |= (1U<<3);	 		        // SET PIN3  i.e enable set pin 3  or turn OFF LED
		}
	}
}