RS232 UART （Universal Asynchronous Receiver / Transmitter）

Serial Input/Oupt

startup running program

• vim /etc/init.d/rcS
• add /bin/helloworld & at the bootom

uart open

#include <stdio.h>

#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

void main()
{
	int fd;
	char *uart3 = "/dev/ttySAC3";

	if ((fd = open(uart3, O_RDWR | O_CREAT, 0777)) < 0)
	{
		printf("open %s failed!\n", uart3);
	}
	else
	{
		printf("open %s is success!\n", uart3);
	}

	close(fd);
}

uart init

• /arch/arm/include/asm/termios.h
• man 3 tcgetattr

uart write

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>

int set_opt(int, int, int, char, int);
void main()
{
	int fd, wr_static, i = 10;
	char *uart3 = "/dev/ttySAC3";
	char *buffer = "hello world!\n";

	printf("\r\nitop4412 uart3 writetest start\r\n");

	if ((fd = open(uart3, O_RDWR | O_NOCTTY | O_NDELAY)) < 0)
	{
		printf("open %s is failed", uart3);
	}
	else
	{
		printf("open %s is success\n", uart3);
		set_opt(fd, 115200, 8, 'N', 1);
		while (i--)
		{
			wr_static = write(fd, buffer, strlen(buffer));
			if (wr_static < 0)
				printf("write failed\n");
			else
			{
				printf("wr_static is %d\n", wr_static);
			}
			sleep(1);
		}
	}
	close(fd);
}

int set_opt(int fd, int nSpeed, int nBits, char nEvent, int nStop)
{
	struct termios newtio, oldtio;
	if (tcgetattr(fd, &oldtio) != 0)
	{
		perror("SetupSerial 1");
		return -1;
	}
	bzero(&newtio, sizeof(newtio));
	newtio.c_cflag |= CLOCAL | CREAD;
	newtio.c_cflag &= ~CSIZE;

	switch (nBits)
	{
	case 7:
		newtio.c_cflag |= CS7;
		break;
	case 8:
		newtio.c_cflag |= CS8;
		break;
	}

	switch (nEvent)
	{
	case 'O':
		newtio.c_cflag |= PARENB;
		newtio.c_cflag |= PARODD;
		newtio.c_iflag |= (INPCK | ISTRIP);
		break;
	case 'E':
		newtio.c_iflag |= (INPCK | ISTRIP);
		newtio.c_cflag |= PARENB;
		newtio.c_cflag &= ~PARODD;
		break;
	case 'N':
		newtio.c_cflag &= ~PARENB;
		break;
	}

	switch (nSpeed)
	{
	case 2400:
		cfsetispeed(&newtio, B2400);
		cfsetospeed(&newtio, B2400);
		break;
	case 4800:
		cfsetispeed(&newtio, B4800);
		cfsetospeed(&newtio, B4800);
		break;
	case 9600:
		cfsetispeed(&newtio, B9600);
		cfsetospeed(&newtio, B9600);
		break;
	case 115200:
		cfsetispeed(&newtio, B115200);
		cfsetospeed(&newtio, B115200);
		break;
	case 460800:
		cfsetispeed(&newtio, B460800);
		cfsetospeed(&newtio, B460800);
		break;
	default:
		cfsetispeed(&newtio, B9600);
		cfsetospeed(&newtio, B9600);
		break;
	}
	if (nStop == 1)
		newtio.c_cflag &= ~CSTOPB;
	else if (nStop == 2)
		newtio.c_cflag |= CSTOPB;
	newtio.c_cc[VTIME] = 0;
	newtio.c_cc[VMIN] = 0;
	tcflush(fd, TCIFLUSH);
	if ((tcsetattr(fd, TCSANOW, &newtio)) != 0)
	{
		perror("com set error");
		return -1;
	}
	//	printf("set done!\n\r");
	return 0;
}

uart read

#include <stdio.h>
#include <string.h>
#include <unistd.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <termios.h>
#include <errno.h>

int set_opt(int, int, int, char, int);
//"/dev/ttySAC3"是con2，靠近耳机接口的串口
void main()
{
	int fd, nByte;
	char *uart3 = "/dev/ttySAC3";
	char buffer[512];
	char *uart_out = "please input\r\n";
	memset(buffer, 0, sizeof(buffer));
	if ((fd = open(uart3, O_RDWR | O_NOCTTY)) < 0)
		printf("open %s is failed", uart3);
	else
	{
		set_opt(fd, 115200, 8, 'N', 1);
		write(fd, uart_out, strlen(uart_out));
		while (1)
		{
			while ((nByte = read(fd, buffer, 512)) > 0)
			{
				buffer[nByte + 1] = '\0';
				write(fd, buffer, strlen(buffer));
				memset(buffer, 0, strlen(buffer));
				nByte = 0;
			}
		}
	}
}

int set_opt(int fd, int nSpeed, int nBits, char nEvent, int nStop)
{
	struct termios newtio, oldtio;
	if (tcgetattr(fd, &oldtio) != 0)
	{
		perror("SetupSerial 1");
		return -1;
	}
	bzero(&newtio, sizeof(newtio));
	newtio.c_cflag |= CLOCAL | CREAD;
	newtio.c_cflag &= ~CSIZE;

	switch (nBits)
	{
	case 7:
		newtio.c_cflag |= CS7;
		break;
	case 8:
		newtio.c_cflag |= CS8;
		break;
	}

	switch (nEvent)
	{
	case 'O':
		newtio.c_cflag |= PARENB;
		newtio.c_cflag |= PARODD;
		newtio.c_iflag |= (INPCK | ISTRIP);
		break;
	case 'E':
		newtio.c_iflag |= (INPCK | ISTRIP);
		newtio.c_cflag |= PARENB;
		newtio.c_cflag &= ~PARODD;
		break;
	case 'N':
		newtio.c_cflag &= ~PARENB;
		break;
	}

	switch (nSpeed)
	{
	case 2400:
		cfsetispeed(&newtio, B2400);
		cfsetospeed(&newtio, B2400);
		break;
	case 4800:
		cfsetispeed(&newtio, B4800);
		cfsetospeed(&newtio, B4800);
		break;
	case 9600:
		cfsetispeed(&newtio, B9600);
		cfsetospeed(&newtio, B9600);
		break;
	case 115200:
		cfsetispeed(&newtio, B115200);
		cfsetospeed(&newtio, B115200);
		break;
	case 460800:
		cfsetispeed(&newtio, B460800);
		cfsetospeed(&newtio, B460800);
		break;
	default:
		cfsetispeed(&newtio, B9600);
		cfsetospeed(&newtio, B9600);
		break;
	}
	if (nStop == 1)
		newtio.c_cflag &= ~CSTOPB;
	else if (nStop == 2)
		newtio.c_cflag |= CSTOPB;
	newtio.c_cc[VTIME] = 0;
	newtio.c_cc[VMIN] = 0;
	tcflush(fd, TCIFLUSH);
	if ((tcsetattr(fd, TCSANOW, &newtio)) != 0)
	{
		perror("com set error");
		return -1;
	}

	//	printf("set done!\n\r");
	return 0;
}