程序代码：
uart4.h：
#ifndef __UART4_H__
#define __UART4_H__
#include"stm32mp1xx_gpio.h"
#include"stm32mp1xx_rcc.h"
#include"stm32mp1xx_uart.h"
void uart4_config();
void putchar(char dat);
char getchar();
void puts(char *s);
void gets(char *s);
#endifuart4.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//PB2GPIOB->MODER &= (~(0x3<<4));GPIOB->MODER |= (0x2<<4);//PG11GPIOG->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115200USART4->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);
}//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('\r');//回车//换行putchar('\n');
}
//接收字符串
void gets(char *s)
{while(1){*s=getchar();//循环接收单个字符，检测到回车键被按下，结束'\r'if(*s=='\r'){break;}putchar(*s);s++;}//在接收的字符串最后补上一个'\0'*s='\0';//发送一个'\n'表示在串口下一行进行显示putchar('\n');
}main.c：
#include "uart4.h"
//手动封装延时函数
void delay_ms(int ms)
{int i,j;for(i=0;i<ms;i++){for(j=0;j<2000;j++){}}
}
int main()
{//uart4初始化uart4_config();char s[128];while(1){gets(s);puts(s);}return 0;
}运行结果：
2、通过串口发送指令，控制LED\蜂鸣器等外设工作
程序代码：
uart4.h:
#ifndef __UART4_H__
#define __UART4_H__
#include "stm32mp1xx_gpio.h"
#include "stm32mp1xx_rcc.h"
#include "stm32mp1xx_uart.h"
void led_init();
void uart4_init();
void myputchar(char i);
char mygetchar();
void puts(char *s);
char *gets();
int mystrcmp(char *dest, char *src);#endifuart4.c:
#include "uart4.h"char buf[51] = {0};
// led数据初始化
void led_init()
{// 设置GPIOE/GPIOF时钟使能RCC->MP_AHB4ENSETR |= (0x3 << 4);// 设置PE10/PE8/PF10为输出模式GPIOE->MODER &= (~(0x3 << 20));GPIOE->MODER |= (0x1 << 20);GPIOE->MODER &= (~(0x3 << 16));GPIOE->MODER |= (0x1 << 16);GPIOF->MODER &= (~(0x3 << 20));GPIOF->MODER |= (0x1 << 20);// 设置PE10/PE8/PF10为推挽输出GPIOE->OTYPER &= (~(0x1 << 10));GPIOE->OTYPER &= (~(0X1 << 8));GPIOF->OTYPER &= (~(0x1 << 10));// 设置PE10/PE8/PF10输出速度为低速GPIOE->OSPEEDR &= (~(0x3 << 20));GPIOE->OSPEEDR &= (~(0X3 << 16));GPIOF->OSPEEDR &= (~(0x3 << 20));// 设置PE10/PE8/PF10无上拉下拉GPIOE->PUPDR &= (~(0x3 << 20));GPIOE->PUPDR &= (~(0X3 << 16));GPIOF->PUPDR &= (~(0X3 << 20));
}// 串口数据初始化
void uart4_init()
{// 设置UART4的RCC时钟使能// RCC_MP_APB1ENSETR[16]->1RCC->MP_APB1ENSETR |= (0x1 << 16);// 设置GPIOB和GPIOG的时钟使能// RCC_MP_AHB4ENSETR[6]->1// RCC_MP_AHB4ENSETR[1]->1RCC->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]->10GPIOG->MODER &= (~(0X3 << 22));GPIOG->MODER |= (0X2 << 22);// GPIOG_AFRH[15:12]->0110GPIOG->AFRH &= (~(0xf << 12));GPIOG->AFRH |= (0x6 << 12);// PB2// GPIOB_MODER[5:4]->10// GPIOB_AFRL[11:8]->1000GPIOB->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]-》0USART4->CR1 &= (~(0X1 << 28));USART4->CR1 &= (~(0X1 << 12));// 设置没有校验位CR1[10]->0USART4->CR1 &= (~(0X1 << 10));// 设置1个停止位CR2[13:12]->00USART4->CR2 &= (~(0x3 << 12));// 设置16倍采样 CR1[15]->0USART4->CR1 &= (~(0X1 << 15));// 设置波特率为115200 BRR=0X22BUSART4->BRR |= 0X22B;// 设置1分频 PRESC[3:0]->0000USART4->PRESC &= (~(0XF));// 使能发送器 CR1[3]->1USART4->CR1 |= (0X1 << 3);// 使能接收器 CR1[2]->1USART4->CR1 |= (0X1 << 2);// 使能串口 CR1[0]->1USART4->CR1 |= (0X1);
}
// 封装函数发送一个字符数据
void myputchar(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
}
char mygetchar()
{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;
}// 输出一个字符串
void puts(char *s)
{while (*s){myputchar(*s++);}myputchar('\n'); // 切换到下一行myputchar('\r'); // 切换到一行的开头
}// 读取一个字符串
char *gets()
{unsigned int i;for (i = 0; i < 50; i++){buf[i] = mygetchar();myputchar(buf[i]);if (buf[i] == '\r')break;}buf[i] = '\0';myputchar('\n');myputchar('\r');return buf;
}int mystrcmp(char *dest, char *src)
{while (*dest && *src){if (*dest != *src)return *dest - *src;dest++;src++;}if (*dest == *src)return 0;
}main.c:
#include "uart4.h"int main()
{led_init();// 1.串口的初始化uart4_init();char *str;// char a;// 现象是发送一个a串口工具打印一个bwhile (1){str = gets();puts(str);// // 2.从串口读取一个字符// a = mygetchar();// // 3.将读取到的字符+1发送回去// myputchar(a + 1);if (mystrcmp(str, "led1_on") == 0)GPIOE->ODR |= (0x1 << 10);else if (mystrcmp(str, "led1_off") == 0)GPIOE->ODR &= ~(0x1 << 10);else if (mystrcmp(str, "led2_on") == 0)GPIOF->ODR |= (0x1 << 10);else if (mystrcmp(str, "led2_off") == 0)GPIOF->ODR &= ~(0x1 << 10);else if (mystrcmp(str, "led3_on") == 0)GPIOE->ODR |= (0x1 << 8);else if (mystrcmp(str, "led3_off") == 0)GPIOE->ODR &= ~(0x1 << 8);}return 0;
}
