Linux 下串口编程实例

朴灿烈づ我的快乐病毒、 2022-12-11 02:19 149阅读 0赞

# Linux 下串口编程实例 #

如下代码实现了uart配置，同时封装了初始化函数、串口读、串口写以便移植，直接看代码吧

#include <stdio.h>
    #include <stdlib.h>
    #include <unistd.h>
    #include <sys/types.h>
    #include <sys/stat.h>
    #include <fcntl.h>
    #include <termios.h>
    #include <errno.h>
    
    #define  TRUE    0
    #define  FALSE  -1
    
    
    unsigned char CharToHex(unsigned char bHex)
    {
    	if((bHex>=0)&&(bHex<=9))
    	{
    		bHex += 0x30;
    	}
    	else if((bHex>=10)&&(bHex<=15))//Capital
    	{
    		bHex += 0x37;
    	}
    	else 
    	{
    		bHex = 0xff;
    	}
    	return bHex;
    }
     
    
    unsigned char HexToChar(unsigned char bChar)
    {
    	if((bChar>=0x30)&&(bChar<=0x39))
    	{
    		bChar -= 0x30;
    	}
    	else if((bChar>=0x41)&&(bChar<=0x46)) // Capital
    	{
    		bChar -= 0x37;
    	}
    	else if((bChar>=0x61)&&(bChar<=0x66)) //littlecase
    	{
    		bChar -= 0x57;
    	}
    	else 
    	{
    		bChar = 0xff;
    	}
    	return bChar;
    }
     
    
    /**
    *@brief  设置串口通信速率
    *@param  fd     类型 int  打开串口的文件句柄
    *@param  speed  类型 int  串口速度
    *@return  void*/
    
    int speed_arr[] = { B38400, B19200, B9600, B4800, B2400, B1200, B300,
    	    B38400, B19200, B9600, B4800, B2400, B1200, B300, };
    int name_arr[] = {38400,  19200,  9600,  4800,  2400,  1200,  300,
    	    38400,  19200,  9600, 4800, 2400, 1200,  300, };
    void set_speed(int fd, int speed)
    {
    	int i;
    	int status;
    	struct termios Opt;
    
    	tcgetattr(fd, &Opt);
    	for ( i= 0; i < sizeof(speed_arr) / sizeof(int); i++) {
    		if (speed == name_arr[i])	{
    			tcflush(fd, TCIOFLUSH);
    			cfsetispeed(&Opt, speed_arr[i]);
    			cfsetospeed(&Opt, speed_arr[i]);
    			status = tcsetattr(fd, TCSANOW, &Opt);
    			if (status != 0)
    				perror("tcsetattr fd1");
    			return;
    		}
    		tcflush(fd,TCIOFLUSH);
    	}
    }
    
    /**
    *@brief   设置串口数据位，停止位和效验位
    *@param  fd     类型  int  打开的串口文件句柄*
    *@param  databits 类型  int 数据位   取值 为 7 或者8*
    *@param  stopbits 类型  int 停止位   取值为 1 或者2*
    *@param  parity  类型  int  效验类型 取值为N,E,O,,S
    */
    int set_parity(int fd,int databits,int stopbits,int parity)
    {
    	struct termios options;
    	if ( tcgetattr(fd, &options) != 0)
    	{
    		perror("SetupSerial 1");
    		return FALSE;
    	}
    	options.c_cflag &= ~CSIZE;
    	switch (databits) {/*设置数据位数*/
    	case 7:
      		options.c_cflag |= CS7;
      		break;
      	case 8:
    		options.c_cflag |= CS8;
    		break;
    	default:
    		fprintf(stderr,"Unsupported data size\n");
    		return FALSE;
    	}
    
    	switch (parity) {
      	case 'n':
    	case 'N':
    		options.c_cflag &= ~PARENB;   /* Clear parity enable */
    		options.c_iflag &= ~INPCK;     /* Enable parity checking */
    		break;
    	case 'o':
    	case 'O':
    		options.c_cflag |= (PARODD | PARENB);  /* 设置为奇效验*/ 
    		options.c_iflag |= INPCK;             /* Disnable parity checking */
    		break;
    	case 'e':
    	case 'E':
    		options.c_cflag |= PARENB;     /* Enable parity */
    		options.c_cflag &= ~PARODD;   /* 转换为偶效验*/  
    		options.c_iflag |= INPCK;       /* Disnable parity checking */
    		break;
    	case 'S':
    	case 's':  /*as no parity*/
    		options.c_cflag &= ~PARENB;
    		options.c_cflag &= ~CSTOPB;
    		break;
    	default:
    		fprintf(stderr,"Unsupported parity\n");
    		return FALSE;
    	}
    
    	/* 设置停止位*/   
    	switch (stopbits) {
      	case 1:
      		options.c_cflag &= ~CSTOPB;
    		break;
    	case 2:
    		options.c_cflag |= CSTOPB;
    		break;
    	default:
    		fprintf(stderr,"Unsupported stop bits\n");
    		return FALSE;
    	}
    
    	/* Set input parity option */
    	if (parity != 'n')
      		options.c_iflag |= INPCK;
    	options.c_cc[VTIME] = 150; // 15 seconds
    	options.c_cc[VMIN] = 0;
    	options.c_cflag &= ~CRTSCTS; //不使用流控制
    
        options.c_iflag &= ~(IGNBRK | BRKINT | PARMRK | ISTRIP
                       | INLCR | IGNCR | ICRNL | IXON);
        options.c_oflag &= ~OPOST;
        options.c_lflag &= ~(ECHO | ECHONL | ICANON | ISIG | IEXTEN);
        options.c_cflag &= ~(CSIZE | PARENB);
        options.c_cflag |= CS8;
    
    
    	tcflush(fd,TCIFLUSH); /* Update the options and do it NOW */
    	if (tcsetattr(fd,TCSANOW,&options) != 0) {
    		perror("SetupSerial 3");
    		return FALSE;
    	}
    
    	return TRUE;
    }
    
    
    /**
    *@breif 打开串口
    */
    int open_dev(char *Dev)
    {
    int	fd = open( Dev, O_RDWR | O_NOCTTY );         //| O_NOCTTY | O_NDELAY
    	if (-1 == fd)
    		{ /*设置数据位数*/
    			perror("Can't Open Serial Port");
    			return -1;
    		}
    	else
    	return fd;
    
    }
    
    int  fd;
    char *dev = "/dev/ttyS4";
    int  speed = 19200;
    
    int ttySX_read(int fd, void *buf, int count)
    {
    	int ret = read(fd, buf, count);
    	if(ret < 0){
    		printf("read error!\n");
    		return -1;
    	}
    
    	return ret;
    }
    
    
    int ttySX_write(int fd, const void *buf, int count)
    {
    	int ret = write(fd, buf, count);
    	if(ret < 0){
    		printf("write error!\n");
    		return -1;
    	}
    
    	return ret;
    }
    
    
    int ttySX_init(int *fd, char *dev, int speed)
    {
    	if ( (*fd = open_dev(dev)) > 0) {
    		set_speed(*fd, speed);
    		printf("open %s successfully!\n", dev);
        } else {
    		printf("Can't Open Serial Port!\n");
    		exit(0);
    	}
    
    	if ( set_parity(*fd, 8, 1, 'N') == FALSE) {
    		printf("Set Parity Error\n");
    		exit(1);
    	}
    }
    
    int uart_rx(char *buf)
    {
    	printf("---->uart_rx\n");
    }
    
    void uart_tx(char *cmd)
    {
    	printf("---->uart_tx:0x%02x\n", *cmd);
    	ttySX_write(fd, cmd, 1);
    }
    
    int main(int argc, char **argv)
    {
    	int lread, lwrite;
    	//int fd;
    	char *dev = "/dev/ttyS4";
    	int  speed = 19200;
    	char buff[8] = {0};
    	char recvbuff[16] = {0};
    	int count = 0;
    	unsigned char cmd[11] = {0x01,0x02,0x03,0x04,0x05,0x06,0x07,0x08,0x09,0x0a,0x0b};
    	unsigned char powerval = 0xFA;
    
    	ttySX_init(&fd, dev, speed);
    	//ttySX_write(fd, "Uart initiallize done\n", 32);
    
    	int arg = atoi(argv[1]);
    	printf("arg:%d\n",arg);
    	if(arg < 12) {
    		uart_tx(cmd + arg - 1);
    	} else if(arg > 150 && arg <= 250){
    		powerval = 0x96 + arg - 150;
    		uart_tx(&powerval);
    	}
    #if 1
    	while(1) {
    
       		
    	  	while((lread = read(fd,buff,8)) > 0) {
      		    printf("------->while(...)\n");
          		printf("Len %d\n",lread);
          		buff[lread+1]='\0';
          		printf("%s\n",buff);
          		for(int i=0; i< lread;i++)
          			printf("0x%02x ", buff[i]);
          		printf("\n");
       		}
       	 }
    
    #endif	
    
       	return 0;
    }

**注意事项：**

1. 确认接收设备与发送设备波特率、数据位长度、停止位数、有无校验位、有无流量控制设置，主从设备上述参数是否统一；

2. 主控收发？从设备收发？

单独将设备rx，tx接到串口工具上，在windows上通过调试助手与设备调试。特别注意接线，过程可以用示波器或者逻辑分析仪确认是否有数据，以及数据对不对；

3. 确认数据收发格式，是hex还是text？

数据以字节流收发，但是不管什么方式，数据都是16进制。

4. 示波器上有数据发出，但是没有收到？

可能是线接错了，rx对tx，tx对rx。如果接线比较乱，建议把梅根线贴上标签，标明tx、rx

5.确认串口属性设置，数据收发是否是raw原始数据（不经过tty系统处理）,实现方法：

**参考链接：**

[https://www.ibm.com/developerworks/cn/linux/l-serials/][https_www.ibm.com_developerworks_cn_linux_l-serials]

[https://blog.csdn.net/lhl\_blog/article/details/82254056][https_blog.csdn.net_lhl_blog_article_details_82254056]

[https_www.ibm.com_developerworks_cn_linux_l-serials]: https://www.ibm.com/developerworks/cn/linux/l-serials/
[https_blog.csdn.net_lhl_blog_article_details_82254056]: https://blog.csdn.net/lhl_blog/article/details/82254056