ARM课程发送一个字符，接收一个字符

fun.c

#include "my_typ_head.h"
 
//初始化
void uart_init()
{
    //1.使能GPIOB/GPIOG/UART4时钟  RCC_MP_AHB4ENSETR/RCC_MP_APB1ENSETR
    //设置GPIOB\GPIOG控制器时钟使能  0X50000A28
    (*(unsigned int *)0X50000A28) |= (0X10);
    (*(unsigned int *)0X50000A28) |= (0X1<<6);
    //设置UART4时钟使能
    (*(unsigned int *)0X50000A00) |= (0X1<<16);
    //2.设置PG11/PB2为复用功能  GPIOX_MODER
    GPIOG->MODER &=(~(0X3<<22));
    GPIOG->MODER |=(0X2<<22);
    GPIOB->MODER &=(~(0X3<<4));
    GPIOB->MODER |=(0X2<<4);
    //3.PG11/PB2为uart4复用功能  GPIOX_AFRL/GPIOX_AFRH
    GPIOB->AFRL |=(0X1000<<8);
    GPIOG->AFRH |=(0X0110<<12);
    //4.设置数据位宽为8位  USART_CR1
    USART4->CR1 &= (~(0X1<<28));
    USART4->CR1 &= (~(0X1<<12));
    //5.设置16倍过采样USART_CR1
    USART4->CR1 &=(~(0X1<<15));
    //6.设置无校验  USART_CR1
    USART4->CR1 &=(~(0X1<<10));
    //7.设置停止位  USART_CR2
    USART4->CR1 &=(~(0X3<<12));
    //8.设置波特率  USART_BRR
    USART4->BRR |=(0X22B);
    //9.发送器使能  USART_CR1
    USART4->CR1 |=(0X1<<3);
    //10.接收器使能  USART_CR1
    USART4->CR1 |=(0X1<<2);
    //11.串口使能  USART_CR1
    USART4->CR1 |=(0X1);
 
}
 
char readchar()
{
    char c;
    //1.判断接收数据寄存器数据是否准备好  USART_ISR[5]
    while(!(USART4->ISR&(0X1<<5)));
    //2.如果准备好就读取  USART_RDR
    c=USART4->RDR;
    //3.返回  
    return c;
}
 
void sendchar(char c)
{
    //1.判断发送数据寄存器是否不满USART_ISR[7]
    while(!(USART4->ISR&(0X1<<7)));
    //2.如果不满就写入  USART_TDR
    USART4->TDR=c;
    //3.等到发送完成后函数结束  USART_ISR[6]
    while(!(USART4->ISR&(0X1<<6)));
}

main.c

#include "my_typ_head.h"
 
int main()
 
{
 
//初始化
 
	uart_init();
 
	char c='A';
 
    while(1)
 
    {
 
    //2.接收一个字节数据
 
	readchar();
 
    //3.发送一个字节数据
 
	sendchar(c);
 
	}
 
    return 0;
 
}

head.h

#ifndef __GPIO_H__
#define __GPIO_H__
#include "/home/ubuntu/xiangmu/kaifaban_c/02-c/common/include/stm32mp1xx_gpio.h"
#include "/home/ubuntu/xiangmu/kaifaban_c/02-c/common/include/stm32mp1xx_rcc.h"
#include "/home/ubuntu/xiangmu/kaifaban_c/02-c/common/include/stm32mp1xx_uart.h"
 
 
void uart_init();
char readchar();
void sendchar(char c);
#endif //__GPIO_H__