/**
  **************************************************************************************************
  * @file		usart.c
  * @author		Kerem Yollu & Edwin Koch
  * @date		03.11.2021
  * @version	0.4 Unstable
  ************************************************************************************************** 
  * @brief		Implementation of usart.h for the STM32F042K6 MCU
  * 
  * **Detailed Description :**
  * 
  * This source code uses bit manipulation in order to minimise the footprint of pin initialisation 
  * and manipulation. It's based on the CMSIS/Device/ST/STM32F0xx/Include/stm32f042x6.h Header file
  * to get the obtain the right Registers. 
  *
  *
  **************************************************************************************************
*/

#include"usart.h"
#include"pin.h"


#define USART2_EN (1U << 17)
#define CR1_TE_EN (1U << 3)
#define CR1_UE_EN (1U << 0)

#define ISR_TXE (1U << 7)

#define UART_BAUD 115200
#define SYST_CLK 8000000
#define AF1 0x01

void usartSetBaudRate(uint32_t baud);

void usartInit()
{
	/* COnfiguring teh pins for the uart*/ 
	pinConfig(pinA2, alternate, def_stage, def_res, def_speed);
	pinConfig(pinA15, alternate, def_stage, def_res, def_speed);
		
	//Sets pina2 to alternate mode as UART_TX
	pinSetAlternate(pinA2, AF1);

	//Enable the priferas bus and UART
	RCC->APB1ENR |= USART2_EN; 	

	usartSetBaudRate(UART_BAUD);
	
	//enables the transmit and sets all the other values to 0 = Default 
	USART2->CR1 = CR1_TE_EN; // The = 0 is on purpose to set uart to default mode.    
	
	//UART Enable
	USART2->CR1 |= CR1_UE_EN; 	
}

static uint16_t usartComputeBaudRate(uint32_t clk, uint32_t baud)
{
	//return((clk + (baud/2U))/baud);
	return(clk/baud);
}	

void usartSetBaudRate(uint32_t baud)
{
	USART2->BRR = usartComputeBaudRate(SYST_CLK,baud); 
}

void usartSendChar(int ch)
{
	// Make sure that TX buffer is empty 
	while(!(USART2->ISR & ISR_TXE)){}
	USART2->TDR = (ch & 0xFF); 
}