樹莓派c語言串口通訊程序

在網上搜了很多關於樹莓派串口通訊的例子，但是都是用python寫的，雖然python很有名，而且最近也在學習這門語言，

但是還是想用c語言實現一下，因爲需要用到整套系統裏，其他內容都是用c語言寫的。但是網上沒有找打現成的。

還好，之前做過天嵌2440開發板的串口程序（參照天嵌工程師提供的代碼），發現串口程序其實是通用的，

驅動層屏蔽了硬件細節，個人猜測，幾乎所有移植好的系統的串口，都可以用一樣的代碼來操作，至少2440和樹莓派是通用的。

分享代碼如下：

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>
#include <ctype.h>
#include <stdio.h>
#include <stdlib.h>
#include <string.h>
#include <time.h>
#include <unistd.h>
#include"pthread.h"
#include "serial.h"


struct serial_config serialread;

static int serial_fd;

int speed_arr[] = {B230400, B115200, B57600, B38400, B19200, B9600, B4800, B2400, B1200, B300,
		   B38400, B19200, B9600, B4800, B2400, B1200, B300};

int name_arr[] = {230400, 115200, 57600, 38400, 19200, 9600, 4800, 2400, 1200, 300,
		  38400, 19200, 9600, 4800, 2400, 1200, 300};

//-----------------------------------------------
//打印配置文件serial.cfg的內容
//-----------------------------------------------
void print_serialread()
{
	printf("serialread.dev is %s\n",serialread.serial_dev);
	printf("serialread.speed is %d\n",serialread.serial_speed);
	printf("serialread.databits is %d\n",serialread.databits);
	printf("serialread.stopbits is %d\n",serialread.stopbits);
	printf("serialread.parity is %c\n",serialread.parity);
}

//-----------------------------------------------
//讀取serial.cfg文件並進行配置
//-----------------------------------------------
void readserialcfg()
{
	FILE *serial_fp;
	char j[10];
	
	printf("readserailcfg\n");

	serial_fp = fopen("./serial.cfg","r");
	if(NULL == serial_fp)
	{
		printf("can't open serial.cfg");
	}
	else
	{
		fscanf(serial_fp, "DEV=%s\n", serialread.serial_dev);

		fscanf(serial_fp, "SPEED=%s\n", j);
		serialread.serial_speed = atoi(j);

		fscanf(serial_fp, "DATABITS=%s\n", j);
		serialread.databits = atoi(j);

		fscanf(serial_fp, "STOPBITS=%s\n", j);
		serialread.stopbits = atoi(j);

		fscanf(serial_fp, "PARITY=%s\n", j);
		serialread.parity = j[0];
	}

	fclose(serial_fp);
}

//-----------------------------------------------
//設置波特率
//-----------------------------------------------
void set_speed(int fd)
{
	int i;
	int status;
	struct termios Opt;
	struct termios oldOpt;
	tcgetattr(fd, &oldOpt);
//	printf("serialread.speed is %d\n",serialread.serial_speed);
	for( i = 0; i < sizeof(speed_arr)/sizeof(int); i++)
	{
		if(serialread.serial_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);
		}
	}
}


//-----------------------------------------------
//設置其他參數
//-----------------------------------------------
int  (int fd)
{
	struct termios options;
	struct termios oldoptions;
	if(tcgetattr(fd, &oldoptions) != 0)
	{
		perror("SetupSerial 1");
		return(FALSE);
	}

	options.c_cflag |= (CLOCAL|CREAD);
	options.c_cflag &=~CSIZE;
//	printf("serialread.databits is %d\n",serialread.databits);
	switch(serialread.databits)
	{
		case 7:
			options.c_cflag |= CS7;
			break;
		case 8:
			options.c_cflag |= CS8;
			break;
		default:
			options.c_cflag |= CS8;
			fprintf(stderr, "Unsupported data size\n");
			return(FALSE);
	}
//	printf("serialread.parity is %c\n",serialread.parity);
	switch(serialread.parity)
	{
		case 'n':
		case 'N':
			options.c_cflag &= ~PARENB;
			options.c_iflag &= ~INPCK;
			break;
		case 'o':
		case 'O':
			options.c_cflag |= (PARODD | PARENB);
			options.c_iflag |= INPCK;
			break;
		case 'e':
		case 'E':
			options.c_cflag |= PARENB;
			options.c_cflag &= ~PARODD;
			options.c_iflag |= INPCK;
			break;
		default:
			options.c_cflag &= ~PARENB;
			options.c_iflag &= ~INPCK;
			fprintf(stderr, "Unsupported parity\n");
			return(FALSE);
	}
//	printf("serialread.stopbits is %d\n",serialread.stopbits);
	switch(serialread.stopbits)
	{
		case 1:
			options.c_cflag &= ~CSTOPB;
			break;
		case 2:
			options.c_cflag |= CSTOPB;
			break;
		default:
			options.c_cflag &= ~CSTOPB;
			fprintf(stderr, "Unsupported stop bits\n");
			return(FALSE);
	}
	if(serialread.parity != 'n')
		options.c_iflag |= INPCK;
	options.c_cc[VTIME] = 0;	//150;			//15 seconds
	options.c_cc[VMIN] = 0;
#if 1
	options.c_iflag |= IGNPAR|ICRNL;
	options.c_oflag |= OPOST; 
	options.c_iflag &= ~(IXON|IXOFF|IXANY);                     
#endif
	tcflush(fd, TCIFLUSH);
	if(tcsetattr(fd, TCSANOW, &options) != 0)
	{
		perror("SetupSerial 3");
		return(FALSE);
	}
	return(TRUE);
}

//-----------------------------------------------
//打開串口設備
//-----------------------------------------------
int OpenDev(char *Dev)
{
	int fd = open(Dev, O_RDWR, 0);
	if(-1 == fd)
	{
		perror("Can't Open Serial Port");
		return -1;
	}
	else
		return fd;
}

//--------------------------------------------------
//串口初始化
//--------------------------------------------------
void serial_init()
{
	char *Dev;

	int i;

	readserialcfg();
	//print_serialread();
    printf("init serial\n");

	Dev = serialread.serial_dev;
	//打開串口設備
	serial_fd = OpenDev(Dev);

	if(serial_fd > 0)
		set_speed(serial_fd);		//設置波特率
	else
	{
		printf("Can't Open Serial Port!\n");
		exit(0);
	}
	//恢復串口未阻塞狀態
	if (fcntl(serial_fd, F_SETFL, O_NONBLOCK) < 0)
	{
		printf("fcntl failed!\n");
		exit(0);
	}
	//檢查是否是終端設備
#if 0	//如果屏蔽下面這段代碼，在串口輸入時不會有回顯的情況，調用下面這段代碼時會出現回顯現象。
	if(isatty(STDIN_FILENO)==0)
	{
		printf("standard input is not a terminal device\n");
	}
	else
		printf("isatty success!\n");
#endif
	//設置串口參數
	if(set_Parity(serial_fd) == FALSE)
	{
		printf("Set parity Error\n");
		exit(1);
	}

}

int serial_write(char* cmd, int count)
{
    printf("serial write for %d bytes\n",count);
    return write(serial_fd,cmd,count);
}

void serial_close()
{
    printf("close serial\n");
    close(serial_fd);
}

/*
void serial_rw()
{
	int i;
	char buff[512];
	
	int nread,nwrite;

     char buff2[] = "hello!\n";
	nwrite = write(serial_fd,buff2,sizeof(buff2));
	printf("nwrite=%d\n",nwrite);
	while(1)
	{
		if((nread = read(serial_fd,buff,512))>0)
		{ 
			buff[nread] = '\0';
#if 1	//調用這段代碼可以實現回顯，如果配合上面的回顯，就會出現回顯兩次的情況。
			write(serial_fd,buff,nread);
#endif
			printf("recv:%d\n",nread);
#if 1
			for(i=0;i<nread;i++)
			{
				printf("%c",buff[i]);
			}
			printf("\n");
#else
			printf("%s",buff);
			printf("\n");
#endif
		}
	}
 


}
*/
/*
int main(int argc, char **argv)
{
	serial_init();

    char cmd[]={0xfc,0x01,0x01,0x02,0x01,0x00,0x03,0x01,0xcf};
    write(serial_fd,cmd,sizeof(cmd));
    close(serial_fd);
    
	return 0;
//	close(serialread.serial_dev);
//	serial_test(telnum, telmoney);
}
*/

當然，還需要對應的頭文件：

#define FALSE		0
#define TRUE		1

#define WORDLEN 32

struct serial_config
{
	unsigned char serial_dev[WORDLEN];
	unsigned int serial_speed;
	unsigned char databits;
	unsigned char stopbits;
	unsigned char parity;
};

void serial_init();
int serial_write(char* cmd, int count);
void serial_close();

以及分離出來的配置文件：

DEV=/dev/ttyAMA0
SPEED=9600
DATABITS=8
STOPBITS=1
PARITY=N

看到c文件可以發現，main函數被註釋了，因爲是編譯的整個系統，這個文件只提供接口，所以沒有main函數，如果需要，可以去掉註釋。

內容很粗糙，有時間再修繕