uart4.c

#include "uart4.h"

//UART4_RX ====> PB2
//UART4_TX ====> PG11

char rebuf[51] = {0};
//rcc/gpio/uart4初始化
void hal_uart4_init()
{
	/********RCC章节初始化*******/
	//1.使能GPIOB组控制器　MP_AHB4ENSETR[1] = 1
	RCC->MP_AHB4ENSETR |= (0x1 << 1);

	//2.使能GPIOG组控制器  MP_AHB4ENSETR[6] = 1
	RCC->MP_AHB4ENSETR |= (0x6 << 1);

	//3.使能UART4组控制器  MP_AHB4ENSETR[16] = 1	
	RCC->MP_APB1ENSETR |= (0x1 << 16);

	/********GPIO章节初始化*******/
	//1.将PB2和PG11设为复用功能模式
	GPIOB->MODER &= (~(0x3 << 4));//PB2
	GPIOB->MODER |= (0x2 << 4);

	GPIOG->MODER &= (~(0x3 << 22));//PG11
	GPIOG->MODER |= (0x2 << 22);

	//2.设置PB2和PG11引脚复用的功能
	GPIOB->AFRL &= (~(0xF << 8));//PB2
	GPIOB->AFRL |= (0x8 << 8);

	GPIOB->AFRH &= (~(0xF << 12));//PG11
	GPIOB->AFRH |= (0x6 << 12);

	/********UART章节初始化*******/
	//1.设置初始化相关操作
	USART4->CR1 &= (~(0x1 << 12));
	USART4->CR1 &= (~(0x1 << 28));//设置8位数据位

	USART4->CR1 &= (~(0x1 << 15));//设置16倍采样率

	USART4->CR1 &= (~(0x1 << 10));//设置无校验位

	USART4->CR1 |= (0x1 << 3);//设置无发送位使能

	USART4->CR1 |= (0x1 << 2);//设置接收位使能

	USART4->CR1 |= 0x1;//设置串口使能

	//2.设置停止位
	USART4->CR2 &= (~(0x3 << 12));//设置串口位停止位

	//3.设置串口分频
	USART4->PRESC &= (~(0xF));

	//4.设置串口波特率
	USART4->BRR |= 0x22B;

}




//发送一个字符
void hal_put_char(const char str)
{
	//判断发送寄存器是否为空
	while(!(USART4->ISR) & (0x1 << 7))
	{
		USART4->TDR = str;
	}
	//判断是否发送完毕
	while(!(USART4->ISR) & (0x1 << 6))
	{
		return;	
	}
	
}

//发送一个字符串
void hal_put_string(const char* string)
{
	while(*string)
	{
		hal_put_char(*string++);
	}
	hal_put_char('\n');
	hal_put_char('\r');
}

//接收一个字符
char hal_get_char()
{
	char str = 0;
	//判断是否接收到数据
	while(!(USART4->ISR) &(0x1 << 5))
	{
		str = USART4->RDR;
	}
	return str;
}

//接收一个字符串
char* hal_get_string()
{

	int i;
	for(i = 0;i < 50;i++)
	{
		rebuf[i] = hal_get_char();
		hal_put_char(rebuf[i]);
		//判断是否接收完毕
		if(rebuf[i] == '\r')
		{
			break;
		}
	}
	rebuf[i] = '\0';
	hal_put_char('\n');
	hal_put_char('\r');
	return rebuf;

}

uart4.h

#ifndef __UART4_H__
#define __UART4_H__


#include "stm32mp1xx_rcc.h"
#include "stm32mp1xx_gpio.h"
#include "stm32mp1xx_uart.h"



//rcc/gpio/uart4初始化
void hal_uart4_init();

//发送一个字符
void hal_put_char(const char str);

//发送一个字符串
void hal_put_string(const char* string);

//接收一个字符
char hal_get_char();

//接收一个字符串
char* hal_get_string();


#endif

main.c

#include "uart4.h"

int main()

{

	//串口初始化

	hal_uart4_init();

	//char str;

	char *string;

	while(1)

	{

		//串口读取字符

		//str = hal_get_char();

		//将字符+1并发回去

		//hal_put_char(str+1);



		//串口读取字符串

		string = hal_get_string();

		//将字符串发回去

		hal_put_string(string);

	}



    return 0;

}