arm day 6

串口输入字符，会显示源字符+1的字符

src/uart.c

#include"uart.h"
 
void uart4_init()
{
    //设置UART4的RCc时钟使能
    //RCC_MP_APB1ENSETR[16]->1
    RCC->MP_APB1ENSETR |= (0x1<<16);
    //设置GPIOB和GPIOG的时钟使能
    //RCC_MP_AHB4ENSETR[6]->1
    //RCC_MP_AHB4ENSETR[1]->1
    RCC->MP_AHB4ENSETR |= (0x1<<1);
    RCC->MP_AHB4ENSETR |= (0X1<<6);
    //设置PG11和PB2功能复用为UART4功能
    //PG11
    //GPIOG_MODER[23:22]->10
    GPIOG->MODER &= (~(0X3<<22));
    GPIOG->MODER |= (0X2<<22);
    //GPIOG_AFRH[15:12]->0110    
    GPIOG->AFRH &= (~(0xf<<12));
    GPIOG->AFRH |= (0x6<<12);
    //PB2
    //GPIOB_MODER[5:4]->10
    //GPIOB_AFRL[11:8]->1000
    GPIOB->MODER &= (~(0x3<<4));
    GPIOB->MODER |= (0X2<<4);
    GPIOB->AFRL &= (~(0xF<<8));
    GPIOB->AFRL |= (0x8<<8);
    //禁用串口
    USART4->CR1 &=(~0x1);
    //设置数据8个数据位 CR1[28]->0  CR1[12]-》0
    USART4->CR1 &= (~(0X1<<28));
    USART4->CR1 &= (~(0X1<<12));
    //设置没有校验位CR1[10]->0
    USART4->CR1 &= (~(0X1<<10));
    //设置1个停止位CR2[13:12]->00
    USART4->CR2 &= (~(0x3<<12));
    //设置16倍采样 CR1[15]->0
    USART4->CR1 &= (~(0X1<<15));
    //设置波特率为115200 BRR=0X22B
    USART4->BRR |= 0X22B;
    //设置1分频 PRESC[3:0]->0000
    USART4->PRESC &= (~(0XF));
    //使能发送器 CR1[3]->1
    USART4->CR1 |= (0X1<<3);
    //使能接收器 CR1[2]->1
    USART4->CR1 |= (0X1<<2);
    //使能串口 CR1[0]->1
    USART4->CR1 |= (0X1);
 
}
//串口发送一个字符
void putchar(char c)
{
    //判断发送数据寄存器有没有数据，没有数据时可以发送
    while(!(USART4->ISR&(0X1<<7)));
    USART4->TDR=c;//将要发送的数据保存在发送寄存器中
    while(!(USART4->ISR&(0X1<<6)));//数据传输完成，函数结束
}
//串口接受一个字符
char getchar()
{
    char c;
    //判断是否有数据准备好
    while(!(USART4->ISR&(0X1<<5)));//数据传输完成，函数结束
    c=USART4->RDR;
    return c;
    
}
//串口发送一个字符串
//串口接收一个字符串

include/uart.h

#ifndef __UART_H__
#define __UART_H__
#include"stm32mp1xx_uart.h"
#include"stm32mp1xx_gpio.h"
#include"stm32mp1xx_rcc.h"
 
void uart4_init();
void putchar(char c);
char getchar();
#endif

main.c

#include "uart.h"
 
int main()
{
    char c;
    uart4_init();//串口初始化
    while(1)
    {
        //串口数据收发
    //接收一个字符
    c=getchar();
    //发送字符
    putchar(c+1);
    }
    return 0;
}