ARM学习

uart.c

#include "uart4.h"
void uart4_config()
{
    //使能GPIOB\GPIOG\UART4的外设时钟
    RCC->MP_AHB4ENSETR |= (0x1<<1);
    RCC->MP_AHB4ENSETR |= (0x1<<6);
    RCC->MP_APB1ENSETR |= (0x1<<16);
    //设置PG11和PB2为管脚复用功能
    //PB2
    GPIOB->MODER &= (~(0x3<<4));
    GPIOB->MODER |= (0x2<<4);
    //PG11
    GPIOG->MODER &= (~(0x3<<22));
    GPIOG->MODER |= (0x2<<22);
    //设置PG11为UART4_TX功能
    GPIOG->AFRH &= (~(0xf<<12));
    GPIOG->AFRH |= (0X6<<12);
    //设置PB2为UART4_RX功能
    GPIOB->AFRL &= (~(0xf<<8));
    GPIOB->AFRL |= (0X8<<8);
    //设置串口不使能
    USART4->CR1 &= (~0x1);
    //设置8位数据位
    USART4->CR1 &= (~(0x1<<12));
    USART4->CR1 &= (~(0x1<<28));
    //设置没有校验位
    USART4->CR1 &= (~(0x1<<10));
    //设置时钟频率不分频
    USART4->PRESC &= (~0xf);
    //设置16倍过采样
    USART4->CR1 &= (~(0x1<<15));
    //设置1位停止位
    USART4->CR2 &= (~(0x3<<12));
    //设置波特率为115200
    USART4->BRR=0X22B;
    //使能发送器
    USART4->CR1 |= (0X1<<3);
    //使能接收器
    USART4->CR1 |= (0X1<<2);
    //使能串口
    USART4->CR1 |= (0X1<<0);
    //使能ＧＰＩＯ的外设时钟
    RCC-> MP_AHB4ENSETR |=(0x3<<4);
    //设置ＰＥ１０为输出
    GPIOE->MODER &= (~ (0x3<<20));
    GPIOE->MODER |= (0x1<<20);
     //设置ＰＦ１０为输出
    GPIOF->MODER &= (~ (0x3<<20));
    GPIOF->MODER |= (0x1<<20);
     //设置ＰＥ８为输出
    GPIOE->MODER &= (~ (0x3<<16));
    GPIOE->MODER |= (0x1<<16);

     //设置ＰＥ１０为推挽输出
    GPIOE->OTYPER&= (~ (0x1<<10));
    //设置ＰＦ１０为推挽输出
    GPIOF->OTYPER &= (~ (0x1<<10));
    //设置ＰＥ８为推挽输出
    GPIOE->OTYPER&= (~ (0x1<<8));

      //设置ＰＥ１０为低速输出
    GPIOE->OSPEEDR &= (~ (0x3<<20));
      //设置ＰＦ１０为低速输出
    GPIOF->OSPEEDR &= (~ (0x3<<20));
      //设置ＰＥ8为低速输出
    GPIOE->OSPEEDR &= (~ (0x3<<16));

     //设置ＰＥ１０为无上拉下拉电阻
    GPIOE->PUPDR &= (~ (0x3<<20));
     //设置ＰＦ１０为无上拉下拉电阻
    GPIOF->PUPDR &= (~ (0x3<<20));
     //设置ＰＥ８为无上拉下拉电阻
    GPIOE->PUPDR &= (~ (0x3<<16));

    //三盏灯默认是关闭
    GPIOE->ODR&= (~ (0x1<<10));
    GPIOF->ODR &= (~ (0x1<<10));
    GPIOE->ODR&= (~ (0x1<<8));
}

//发送单个字符
void putchar(char dat)
{
    //当发送数据寄存器中没有数据时可以发送
    while (!(USART4->ISR & (0x1<<7)));//当TDR中有数据时阻塞等待没有数据
    USART4->TDR = dat;//向发送数据寄存器中写入数据
    //等大传输完成函数结束
    while (!(USART4->ISR & (0x1<<6)));
}

//接收单个字符
char getchar()
{
    //当接收数据寄存器中有有效数据时读取
    while (!(USART4->ISR & (0x1<<5)));
    //将读取到的数据返回
    return USART4->RDR;

}

//发送字符串
void puts(char *s)
{
    while(1)
    {
        if(*s=='\0')
            break;
        putchar(*s);
        s++;
    }
    //发送一个回车
    putchar('\n');
    putchar('\r');
}

//接收字符串
void gets(char *s)
{
   
     while(1)
     {
        //循环接收单个字符，当检测到回车键‘\r’被按下，结束
        *s=getchar();
        putchar(*s);
        if(*s == '\r')
            break;
        s++;
     } 
     //在接收的字符串最后补上一个'\0'
     *s='\0';
     putchar('\n');
     putchar('\r');
     //发送一个'\n'表示在串口工具下一行进行显示
}

int strcmp(char *s,char *q)
{
    while(*s == *q && *s )
    {
        s++;
        q++;
    }
    return *s -*q;
}

uart.h

#ifndef __UART4_H__
#define __UART4_H__
#include "stm32mp1xx_gpio.h"
#include "stm32mp1xx_uart.h"
#include "stm32mp1xx_rcc.h"
void uart4_config();
void putchar(char dat);
char getchar();
void puts(char *s);
void gets(char *s);
int strcmp(char *s,char *q);
#endif

main.c

#include "uart4.h"

void dealy_ms(int ms)
{
    for(int i = 0;i<ms;i++)
    {
        for(int j = 0;j<2000;j++)
        {

        }
    }
}

int main()
{
 //uart4初始化
    uart4_config();
    char a[40];
    while(1)
    {
        gets(a);
        if( strcmp(a,"on")==0)
        {
          
            GPIOE->ODR |=  (0x1<<10);
            GPIOF->ODR |=  (0x1<<10);
            GPIOE->ODR |= (0x1<<8);
        }
        if(strcmp(a,"off")==0)
        {
            GPIOE->ODR&= (~ (0x1<<10));
            GPIOF->ODR &= (~ (0x1<<10));
            GPIOE->ODR&= (~ (0x1<<8));
        }

        puts(a);  //现象，发送a,输出b
    }
    return 0;
}

效果演示