Linux环境下使用interrupt方式操作UART

概述

1 Linux环境下UART设备

2 轮询方式操作UART功能实现

2.1 打开串口函数：usr_serial_open

2.2 关闭串口函数： usr_serial_close

2.3 发送数据函数： usr_serial_sendbytes

2.4 接收数据函数： usr_serial_readinterrupt

3 完整代码

3.1 usr_serial.c 文件内容

3.1 usr_serial.h 文件内容

4 编写测试代码

4.1 编写测试代码

4.2 编写测试代码的Makefile

5 测试中断模式下串口数据的发送和接收功能

源代码下载地址：Linux环境下使用interrupt方式操作UART资源-CSDN文库

概述

本文介绍Linux环境下使用interrupt方式操作UART的方法，实现了串口打开，关闭，发送数据，接收数据功能，还编写测试代码，验证该功能。

1 Linux环境下UART设备

在linux环境下,UART作为一个终端设备存在，可使用命令，系统会罗列出该目录下所有的device,其中以tty开头的设备为终端设备。串口也是这些设备之一。

ls /dev/ -l

执行该命令后，可以看见许多以tty开头的设备：

user根据板卡的信息，找到对应的端口，然后才能使用这些串口，笔者使用是基于iMX6ull芯片的板卡，板卡上COM1被用于调试终端，COM3可作为用户终端。

2 轮询方式操作UART功能实现

2.1 打开串口函数：usr_serial_open

函数参数

参数	描述
port	终端设备: /dev/tty0
baudrate	波特率： 1200/2400/4800 ... /115200
databit	数据bit位： /5/6/7/8
stopbit	停止位："1" / "1.5" / "2"
parity	奇偶位使能： 'N' / 'E' / 'O'

函数实现方法：

代码 43行：打开端口

代码 49行：保存termios数据结构中，旧的参数

代码 51行：设置当前用户参数

源代码：

int usr_serial_open( char *port, unsigned int baudrate, unsigned int databit, const char *stopbit, char parity)
{int err;fd = open (port, O_RDWR | O_NOCTTY | O_NDELAY);if (-1 == fd) {fprintf(stderr, "cannot open port %s\n", port);return (-1);}tcgetattr (fd, &termios_old);       /* save the form termios value */err = set_portattr (baudrate, databit, stopbit, parity);if ( err ) {fprintf ( stderr, "\nport %s cannot set baudrate at %d\n",port, baudrate);}usr_baudrate = baudrate;return fd;
}

2.2 关闭串口函数： usr_serial_close

函数实现方法：

代码 64行：恢复termios default参数

代码 65行：关闭fd端口

void usr_serial_close( void )
{/* flush output data before close and restore old attribute */tcsetattr(fd, TCSADRAIN, &termios_old);close(fd);
}

2.3 发送数据函数： usr_serial_sendbytes

函数参数

参数	描述
*data	存贮数据的数组
datalength	发送的数据长度

函数实现方法：

代码 72行：使用write函数发送数据

2.4 接收数据函数： usr_serial_readinterrupt

函数参数

参数	描述
*data	存贮数据的数组
datalength	接收的数据长度

函数实现方法：

代码 100~102行：配置接收中断

代码 104行：使用read函数写数据

unsigned int usr_serial_readinterrupt (void *data, unsigned int datalength)
{int total_len = 0;/*** caculate the time of 5 characters and get the maxim* with 3ms and 5 ch's time*/tv_timeout.tv_sec = 0;tv_timeout.tv_usec = ( (CH_TO_WAIT * CH_BITS) * (1000000/usr_baudrate));while(1){FD_ZERO (&fs_read);FD_SET (fd, &fs_read);select (fd + 1, &fs_read, NULL, NULL, &tv_timeout);total_len = read(fd, data, datalength);if (total_len > 0) {printf("Receive %d bytes: %.*s\n", total_len, (char*)data);return total_len;}}return total_len;}

3 完整代码

代码文件命名为usr_serial，包含两个文件

usr_serial.c
usr_serial.h

3.1 usr_serial.c 文件内容

/***************************************************************
Copyright  2024-2029. All rights reserved.
文件名     : 01_usr_serial.c
作者       : tangmingfei2013@126.com
版本       : V1.0
描述       : linux 串口应用程序接口
其他       : 无
日志       : 初版V1.0 2024/03/01***************************************************************/
#include "usr_serial.h"/* Private define ------------------------------------------------------------*/
#define TIMEOUT_SEC(buflen,baud)    (buflen*20/baud+2)
#define TIMEOUT_USEC                 0#define CH_TO_WAIT 5
#define CH_BITS 11/* Private variables ---------------------------------------------------------*/
static unsigned int fd;  static struct timeval tv_timeout;
static struct termios termios_old;
static struct termios termios_new;static fd_set fs_read;
static unsigned int usr_baudrate;/* Private function prototypes -----------------------------------------------*/
static speed_t baudrate_to_Bxx (unsigned int baudrate);
static void set_data_bit (unsigned int databit);
static unsigned int set_portattr ( unsigned int baudrate,unsigned int databit, const char *stopbit,char parity);int usr_serial_open( char *port, unsigned int baudrate, unsigned int databit, const char *stopbit, char parity)
{int err;fd = open (port, O_RDWR | O_NOCTTY | O_NDELAY);if (-1 == fd) {fprintf(stderr, "cannot open port %s\n", port);return (-1);}tcgetattr (fd, &termios_old);       /* save the form termios value */err = set_portattr (baudrate, databit, stopbit, parity);if ( err ) {fprintf ( stderr, "\nport %s cannot set baudrate at %d\n",port, baudrate);}usr_baudrate = baudrate;return fd;
}void usr_serial_close( void )
{/* flush output data before close and restore old attribute */tcsetattr(fd, TCSADRAIN, &termios_old);close(fd);
}unsigned int usr_serial_sendbytes (void * data, unsigned int datalength)
{unsigned int total_len = 0;total_len = write(fd, data, datalength);return (total_len);
}int usr_serial_readbytes (void *data, unsigned int datalength)
{unsigned int total_len = 0;total_len = read(fd, data, datalength);if (total_len > 0) {printf("Receive %d bytes: %.*s\n", total_len, (char*)data);}return (total_len);
}unsigned int usr_serial_readinterrupt (void *data, unsigned int datalength)
{int total_len = 0;/*** caculate the time of 5 characters and get the maxim* with 3ms and 5 ch's time*/tv_timeout.tv_sec = 0;tv_timeout.tv_usec = ( (CH_TO_WAIT * CH_BITS) * (1000000/usr_baudrate));while(1){FD_ZERO (&fs_read);FD_SET (fd, &fs_read);select (fd + 1, &fs_read, NULL, NULL, &tv_timeout);total_len = read(fd, data, datalength);if (total_len > 0) {printf("Receive %d bytes: %.*s\n", total_len, (char*)data);return total_len;}}return total_len;}static void set_data_bit (unsigned int databit)
{termios_new.c_cflag &= ~CSIZE;switch (databit) {default:case 8:termios_new.c_cflag |= CS8;break;case 7:termios_new.c_cflag |= CS7;break;case 6:termios_new.c_cflag |= CS6;break;case 5:termios_new.c_cflag |= CS5;break;}
}static void set_stopbit (const char *stopbit)
{if (0 == strcmp (stopbit, "1")) {termios_new.c_cflag &= ~CSTOPB;    /* 1 stop bit */}else if (0 == strcmp (stopbit, "1.5")) {termios_new.c_cflag &= ~CSTOPB;     /* 1.5 stop bits */}else if (0 == strcmp (stopbit, "2")) {termios_new.c_cflag |= CSTOPB;       /* 2 stop bits */}else {termios_new.c_cflag &= ~CSTOPB;     /* 1 stop bit */}
}static void set_parity (char parity)
{switch (parity) {case 'N':                  /* no parity check */termios_new.c_cflag &= ~PARENB;break;case 'E':                  /* even */termios_new.c_cflag |= PARENB;termios_new.c_cflag &= ~PARODD;break;case 'O':                  /* odd */termios_new.c_cflag |= PARENB;termios_new.c_cflag |= ~PARODD;break;default:                   /* no parity check */termios_new.c_cflag &= ~PARENB;break;}
}static speed_t baudrate_to_Bxx (unsigned int baudrate)
{switch (baudrate) {case 0:return (B0);case 50:return (B50);case 75:return (B75);case 110:return (B110);case 134:return (B134);case 150:return (B150);case 200:return (B200);case 300:return (B300);case 600:return (B600);case 1200:return (B1200);case 2400:return (B2400);case 9600:return (B9600);case 19200:return (B19200);case 38400:return (B38400);case 57600:return (B57600);case 115200:return (B115200);default:return (B9600);}
}static void set_baudrate (unsigned int baudrate)
{speed_t speed;speed = baudrate_to_Bxx (baudrate);  /* set baudrate */cfsetispeed(&termios_new, speed);    // set input speedcfsetospeed(&termios_new, speed);    // set output speed
}static unsigned int set_portattr ( unsigned int baudrate,  // 1200 2400 4800 9600 .. 115200unsigned int databit,   // 5, 6, 7, 8const char *stopbit,    //  "1", "1.5", "2"char parity)            // N(o), O(dd), E(ven)
{bzero(&termios_new, sizeof (termios_new));cfmakeraw (&termios_new);set_baudrate (baudrate);termios_new.c_cflag |= CLOCAL | CREAD;   /* | CRTSCTS */set_data_bit (databit);set_parity (parity);set_stopbit (stopbit);termios_new.c_cc[VTIME] = 1;            /* unit: 1/10 second. */termios_new.c_cc[VMIN]  = 255;          /* minimal characters for reading */return (tcsetattr (fd, TCSANOW, &termios_new));
}/* End of this file */

3.1 usr_serial.h 文件内容

#ifndef __USR_SERIAL_H
#define __USR_SERIAL_H#include <termios.h>            /* tcgetattr, tcsetattr */
#include <stdio.h>              /* perror, printf, puts, fprintf, fputs */
#include <unistd.h>             /* read, write, close */
#include <fcntl.h>              /* open */
#include <sys/signal.h>
#include <sys/types.h>
#include <string.h>             /* bzero, memcpy */
#include <limits.h>             /* CHAR_MAX */#ifdef __cplusplus
extern "C" {
#endifint usr_serial_open( char *port, unsigned int baudrate, unsigned int databit, const char *stopbit, char parity);
void usr_serial_close( void );unsigned int usr_serial_sendbytes (void * data, unsigned int datalength);
int usr_serial_readbytes (void *data, unsigned int datalength);
unsigned int usr_serial_readinterrupt (void *data, unsigned int datalength);#ifdef __cplusplus
}
#endif#endif /* __USR_SERIAL_H */