嵌入式学习Day48（ARM）

cortex-A7UART实验

uart4.h

#ifndef __UART4_H__
#define __UART4_H__
 
#include "stm32mp1xx_gpio.h"
#include "stm32mp1xx_rcc.h"
#include "stm32mp1xx_uart.h"
 
//初始化函数
void hal_uart_init();
 
//发送一个字符
void hal_put_char(const char str);
 
//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();
 
#endif

uart4.c

#include "uart4.h"
//初始化函数
void hal_uart_init()
{
	/******RCC章节初始化******/
	//GPIOB组寄存器使能
	//RCC->MP_AHB4ENSETR &= (~(0x1 << 1));
	RCC->MP_AHB4ENSETR |= (0x1 << 1);
	//GPIOG组寄存器使能
	//RCC->MP_AHB4ENSETR &= (~(0x1 << 6));
	RCC->MP_AHB4ENSETR |= (0x1 << 6);
	//UART4组寄存器使能
	//RCC->MP_APB1ENSETR &= (~(0x1 << 16));
	RCC->MP_APB1ENSETR |= (0x1 << 16);
 
	/******GPIO章节初始化******/
	//设置PB2为复用功能模式
	GPIOB->MODER &= (~(0x3 << 4));
	GPIOB->MODER |= (0x2 << 4);
	//设置PG11为复用功能模式
	GPIOG->MODER &= (~(0x3 << 22));
	GPIOG->MODER |= (0x2 << 22);
	//设置PB2引脚为复用功能
	GPIOB->AFRL &= (~(0xf << 8));
	GPIOB->AFRL |= (0x8 << 8);
	//设置PG11引脚为复用功能
	GPIOG->AFRH &= (~(0xf << 12));
	GPIOG->AFRH |= (0x6 << 12);
 
	/******UART章节初始化******/
	//设置数据位宽度8bit
	USART4->CR1 &= (~(0x1 << 12));
	USART4->CR1 &= (~(0x1 << 28));
	//设置16倍采样率
	USART4->CR1 &= (~(0x1 << 15));
	//设置无奇偶校验位
	USART4->CR1 &= (~(0x1 << 10));
	//设置串口发送器使能
	USART4->CR1 |= (0x1 << 3);
	//设置串口接收器使能
	USART4->CR1 |= (0x1 << 2);
	//设置串口使能
	USART4->CR1 |= (0x1 << 0);
	//设置串口一位停止位
	USART4->CR2 &= (~(0x3 << 12));
	//设置串口波特率
	USART4->BRR &= (~(0xffff));
	USART4->BRR |= (0x22b);
	//设置不分频
	USART4->PRESC &= (~(0xf));
}
 
//发送一个字符
void hal_put_char(const char str)
{
	//1.判断发送寄存器是否为空
	while(!(USART4->ISR & (0x1 << 7)));
	//2.将要发送的数据，放入到发送数据寄存器中
	USART4->TDR &= (~(0x1ff));
	USART4->TDR = str;
	//3.判断发送数据寄存器是否发送完成
	while(!(USART4->ISR & (0x1 << 6)));
}
 
//发送一个字符串
void hal_put_string(const char* string)
{
	//判断是否为'\0',一个字符一个字符进行发送
	while(*string)
	{
		hal_put_char(*string);
		string++;
	}
	hal_put_char('\r');
	hal_put_char('\n');
}
 
//接收一个字符
char hal_get_char()
{
	char ch;
	//1.判断接收数据寄存器中是否有数据可读
	while(!(USART4->ISR & (0x1 << 5)));
	//2.将接收数据寄存器中的内容赋值给ch
	ch = USART4->RDR;
	return ch;
}
 
//定义全局变量
char arr[512] = "0";
//接收一个字符串
char* hal_get_string()
{
	int i=0;
	//循环进行接收
	while(1)
	{
		//1.判断接收数据寄存器中是否有数据可读
		while(!(USART4->ISR & (0x1 << 5)));
		//2.将接收数据寄存器中的内容赋值给arr
		//判断字符是否为'\r',break
		if(USART4->RDR == '\r')
		{
			arr[i] = '\0';
			break;
		}
		arr[i] = USART4->RDR;
		hal_put_char(arr[i]);
		i++;
	}
	hal_put_char('\r');
	hal_put_char('\n');
	return arr;
}

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_uart_init();
 
	while(1)
 
	{
 
		//hal_put_char(hal_get_char() + 1);
 
		hal_put_string(hal_get_string());
 
	}
 
	return 0;
 
}