一、C
1）uart4.h
#ifndef __UART4_H__
#define __UART4_H__
#include "stm32mp1xx_rcc.h"
#include "stm32mp1xx_gpio.h"
#include "stm32mp1xx_uart.h"
//PB2 ---> UART4_RX
//PG11 ---> UART4_TX
//RCC/GPIO/UART4章节初始化
void hal_uart4_init();
//发送一个字符
void hal_put_char(const char ch);
//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();
#endif2）uart.c
#include "uart4.h"
//RCC/GPIO/UART4章节初始化
void hal_uart4_init()
{
//RCC章节初始化
//1.使能GPIOB组控制器 MP_AHB4ENSETR[1] = 1 0x50000A28[1]
RCC->MP_AHB4ENSETR |= (0X1 << 1);
//2.使能GPIOG组控制器 MP_AHB4ENSETR[6] = 1 0x50000a28[6]
RCC->MP_AHB4ENSETR |= (0X1 << 6);
//3.使能UART4组控制器 MP_AHB4ENSETR[11] = 1 PB2 PG11---> 0x500000A00[16]
RCC->MP_APB1ENSETR |= (0X1 << 16);
//GPIO章节初始化
//1.设置PB2引脚为复用功能模式 MODER[5:4] = 10
GPIOB->MODER &= (~(0x1 << 4));
GPIOB->MODER |= (0x1 << 5);
//2.设置PB2引脚复用功能为UART4_RX功能 AFRL[11:8] = 1000
GPIOB->AFRL &= (~(0xf << 8));
GPIOB->AFRL |= (0x1 << 11);
//设置PG11引脚为复用功能模式 MODER[23:22] = 10
GPIOG->MODER &= (~(0x1 << 22));
GPIOG->MODER |= (0x1 << 23);
//设置PG11引脚复用功能为UART4_TX功能 AFRH[15:12] = 0110
GPIOG->AFRH &= (~(0xf << 12));
GPIOG->AFRH |= (0x6 << 12);
//UART4章节初始化
//8N1 115200 使能位 代码编写逻辑
//0.设置串口UE=0 CR1[0] = 0
USART4->CR1 &= (~(0x1 << 0));
//1.设置1位起始位，8位数据位 CR1[28][12] = 00
USART4->CR1 &= (~(0x1 << 12));
USART4->CR1 &= (~(0x1 << 28));
//2.设置串口1位停止位 CR2[13:12] = 00
USART4->CR2 &= (~(0x3 << 12)) ;
//3.设置串口无校验位 CR1[10] = 0
USART4->CR1 &= (~(0x1 << 10));
//4.设置串口16倍采样率 CR1[15] = 0
USART4->CR1 &= (~(0x1 << 15));
//5.设置串口不分频 PRESC[3:0] = 0000
USART4->PRESC &= (~(0xf << 0));
//6.设置串口波特率为115200 BRR = 0X22b
USART4->BRR &= (~(0xffff));
USART4->BRR |= (0x22b);
//7.设置串口发送位使能 CR1[3] = 1
USART4->CR1 |= (0x1 << 3);
//8.设置串口接受位使能 CR1[2] = 1
USART4->CR1 |= (0x1 << 2);
//9.设置串口使能 CR1[0] = 1
USART4->CR1 |= (0x1 << 0);
}
//发送一个字符
void hal_put_char(const char ch)
{
//1.判断发送数据寄存器是否为空 ISR[7]
//读0：发送数据寄存器满，需要等待 for while
//读1：发送数据寄存器空，可以发送数据
while(!(USART4->ISR & (0X1 << 7)));
//2.将参数ch传递过来的内容，赋值给TDR寄存器
USART4->TDR = (volatile unsigned int)ch;
//3.判断一帧数据是否发送完成 ISR[6]
while(!(USART4->ISR & (0x1 << 6)));
}
//发送一个字符串
void hal_put_string(const char* string)
{
//判断字符串是否为'\0'
int i=0;
while(string[i] != '\0')
{
//一个字符一个字符进行发送
hal_put_char(string[i]);
i++;
}
}
//接收一个字符
char hal_get_char()
{
char ch;
//1.判断接收数据寄存器是否不为空 ISR[5]
//读0：没有接收到数据，需要等待 for while
//读1：接收到数据，可以将数据读出
while(!(USART4->ISR & (0x1 << 5)));
//2.将接收数据寄存器中RDR，读出来
ch = (char)USART4->RDR;
return ch;
}
char buffer[50] = {0};
//接收一个字符串
char* hal_get_string()
{
for(int i=0;buffer[i]!='\0'; i++)
{
buffer[i]='\0';
}
//判断键盘enter是否按下'\r'
int i = 0;
char ch;
while(1)
{
ch = hal_get_char();
hal_put_char(ch);
buffer[i] = ch;
i++;
if(ch == '\r')
{
hal_put_char('\n');
break;
}
}
buffer[i] = '\n';
return buffer;
}3）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()
{
hal_uart4_init();
while(1)
{
//单个字符
//hal_put_char(hal_get_char() + 1);
//字符串
hal_put_string(hal_get_string());
}
return 0;
}
4）效果
实验一：收发字符
实验二：收发字符串
二、函数实现
1）uart4.h
2）uart.c
3）main.c
4）效果
实验一：收发字符
实验二：收发字符串
