#include "stm32l0xx.c"
#include <stdint.h>

#define GPIOAEN		    (1U<<0)
#define UART2AEN		(1U<<17)
#define SYS_CLCK 		(16000000UL)
#define APB1_CLK		SYS_CLCK
#define BAUDRATE		(115200UL)
#define CR1_TE 		    (1U<<3)
#define CR1_UE          (1U<<0)
#define ISR_TXE         (1<<7)
static void uart_set_baudrate(USART_TypeDef *USARTx,uint32_t PeriphClk,uint32_t baudrate);
static uint16_t compute_uart_bd(uint32_t PeriphClk,uint32_t baudrate);
void uart2_tx_init(void);

int __io_putchar(int ch){
      uart2_write(ch);
return ch;
}
int main (void)
{
  Serial.begin(115200);
	uart2_tx_init();

	while(1)

	{

		printf("hello STM32 Programmer:\n");
    myDelay();
	 }
	return 0;
}

void uart2_write(int ch)
{
	/*Check Data Register is empty*/
	while(!(USART2->ISR & ISR_TXE));
	/*Write data to data register*/
	USART2->TDR =(ch & 0xff);
}
void uart2_tx_init(void)
{
	/******** configure uart pin********/
	/*Enable clock to access GPIOA*/
	RCC->IOPENR =GPIOAEN;
	/*Set PA2 to alternate function mode*/
	GPIOA->MODER &=~(1<<4);
	GPIOA->MODER |=(1<<5);
	/*Set PA2 alternate function type to uart2_tx AF[04]*/
	GPIOA->AFR[0]  &=~(1<<16);
	GPIOA->AFR[0]  &=~(1<<17);
	GPIOA->AFR[0]  |=(1<<18);
	GPIOA->AFR[0]  &=~(1<<19);
	/******** configure uart module********/
	/*Enable clock to access uart2*/
	RCC->APB1ENR |=  UART2AEN;
	/*Configure baudrate */
	uart_set_baudrate(USART2,APB1_CLK,BAUDRATE);
	/*Configure the transfer direction*/
	USART2->CR1 =CR1_TE;
	/*Enale the uart mode */
	USART2->CR1 |=CR1_UE;

}

static void uart_set_baudrate(USART_TypeDef *USARTx,uint32_t PeriphClk,uint32_t baudrate)
{
	USARTx->BRR=compute_uart_bd(PeriphClk,baudrate);
}
static uint16_t compute_uart_bd(uint32_t PeriphClk,uint32_t baudrate)
{
	return ((PeriphClk+ (baudrate/2U))/baudrate);
}


void myDelay()
{
for(volatile long i=0; i<100000;i++);
}