1.串口发送单个字符

2.串口发送字符串

uart4.h

#ifndef __UART4_H__
#define __UART4_H__

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


//初始化相关操作
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(char* arr);

uart4.c

#include "uart4.h"

//初始化相关操作
void hal_uart4_init()
{
	//----------RCC章节初始化----------//
	//(GPIOB,GPIOG,UART4)
	RCC->MP_AHB4ENSETR |= (0x1 << 1);
	RCC->MP_AHB4ENSETR |= (0x1 << 6);
	RCC->MP_APB1ENSETR |= (0x1 << 16);

	//---------GPIO章节初始化----------//
	//PB2引脚设置复用功能模式
	GPIOB->MODER &= (~(0x3 << 4));
	GPIOB->MODER |= (0x2 << 4);
	//设置为RX
	GPIOB->AFRL &= (~(0xf << 8));
	GPIOB->AFRL |= (0x8 << 8);

	//PG11引脚设置复用功能模式
	GPIOG->MODER &= (~(0x3 << 22));
	GPIOG->MODER |= (0x2 << 22);
	//设置为TX
	GPIOG->AFRH &= (~(0xf << 12));
	GPIOG->AFRH |= (0x6 << 12);

	//----------UART章节初始化----------//
	//设置串口UE = 0
	USART4->CR1 &= (~(0x1));

	//数据位宽度（1个起始位，8个数据位，n个停止位）
	USART4->CR1 &= (~(0x1 << 12));
	USART4->CR1 &= (~(0x1 << 28));

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

	//无奇偶校验
	USART4->CR1 &= (~(0x1 << 10));

	//接收器使能
	USART4->CR1 |= (0x1 << 2);

	//发射器使能
	USART4->CR1 |= (0x1 << 3);

	//设置1位停止位
	USART4->CR2 &= (~(0x3 << 12));

	//设置串口不分频
	USART4->PRESC &= (~(0xf));

	//设置串口波特率为115200
	USART4->BRR = 0x22b;

	//设置串口使能
	USART4->CR1 |= (0x1);
	
}


//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)));

	//将发送的内容赋值给发送寄存器
	USART4->TDR = str;

	//判断一帧数据是否发送完成
	while(!(USART4->ISR & (0x1 << 6)));
}

//发送一个字符串
void hal_put_string(const char* string)
{
	hal_put_char('\n');
	while(*string != '\0')
	{
		//判断发送寄存器是否为空
		while(!(USART4->ISR & (0x1 << 7)));

		//将发送的内容赋值给发送寄存器
		USART4->TDR = *string;
		string++;

		//判断一帧数据是否发送完成
		while(!(USART4->ISR & (0x1 << 6)));
	}
	hal_put_char('\r');
	hal_put_char('\n');
}

/*
//接收一个字符
char hal_get_char()
{
	//判断接收数据寄存器中是否有数据
	while(!(USART4->ISR & (0x1 << 5)));

	//将接收数据寄存器中的数据读取出来
	char str = USART4->RDR;
	return str;
}
*/

//接收一个字符串
char* hal_get_string(char* arr)
{
	//循环进行接收
	//当键盘输入回车之后，代表字符串输出完成
	char *p = arr;
	while(1)
	{
		while(!(USART4->ISR & (0x1 << 5)));
		*p = USART4->RDR;
		hal_put_char(*p);
		while(!(USART4->ISR & (0x1 << 6)));
		if(*p == '\r')
			break;
		p++;
	}
	*p = '\0';
	return arr;
}

main.c

#include "uart4.h"
extern void printf(const char *fmt, ...);
void delay_ms(int ms)
{
	int i,j;
	for(i = 0; i < ms;i++)
		for (j = 0; j < 1800; j++);
}


int main()
{
	char arr[20] = "";
	hal_uart4_init();      //初始化
	while(1)
	{
		//hal_put_char(hal_get_char()+1);      //单个字符
		hal_put_string(hal_get_string(arr));   //字符串
	}
	return 0;
}

实验现象