好久没有写博客了，先从一个小小的程序开始一段新的历程吧；

最近的项目主要还是用的的是linux系统，这篇文章主要介绍如何从设置、读取BD+gps模块（um220），实际上主要是对串口（UART）的操作。

/*
 * gps.c
 *
 * um220 test
 *
 * Author: Wang Zhengkai <449811900@qq.com>
 *
 */
#include <stdio.h>
#include <termios.h>
#include <strings.h>
#include <string.h>
#include <stdlib.h>
#include <fcntl.h>
#include <unistd.h>

/*我用的是ubuntu的电脑测试的，使用的串口是ttyS0*/
#define DEV_NODE "/dev/ttyS0"
#define MAX_PACKET_SIZE 1024

/* Initialize serial port options */
static void setTermios(struct termios * pNewtio, int uBaudRate)
{
	bzero(pNewtio, sizeof(struct termios)); /* clear struct for new port settings */
	//8N1
	pNewtio->c_cflag = uBaudRate | CS8 | CREAD | CLOCAL;
	pNewtio->c_iflag = IGNPAR;
	pNewtio->c_oflag = 0;
	pNewtio->c_lflag = 0; //non ICANON
}

/*设置um220串口的波特率9600，并刷新使其立即生效*/
void um220_uart_init(int ttyFd,struct termios *oldtio,struct termios *newtio)
{


	tcgetattr(ttyFd, oldtio); /* save current serial port settings */
	setTermios(newtio, B9600);
	tcflush(ttyFd, TCIFLUSH);
	tcsetattr(ttyFd, TCSANOW, newtio);
}


/*Analysis Data of um220*/
void parseData(char *buf)
{
	int nQ, nN, nB, nC;
	char cX, cY, cM1, cM2;
	float fTime, fX, fY, fP, fH, fB, fD;

	if (buf == NULL)
	{
		printf("error: Can't get buf!\n");
		return;
	}
	sscanf(buf,"$GNGGA,%f,%f,%c,%f,%c,%d,%02d,%f,%f,%c,%f,%c,%f,%04d%02x",&fTime,&fX,&cX,&fY,&cY,&nQ,&nN,&fP,&fH,&cM1,&fB,&cM2, &fD, &nB, &nC);

	printf("x: %c %f, y: %c %f, h %f, satellite: %d\n",cX, fX, cY, fY, fH, nN);

/*cX：N or S;fX：纬度；cY：E or W；fY：经度；fH：height；nN：卫星个数*/
}


int main(void)
{
	int nb,command;
	int um220_fd = -1;
	char newbuf[MAX_PACKET_SIZE];
	char msg[20],*ret=NULL;
	struct termios oldtio, newtio;

	/*Open Um220 Module*/
	if ((um220_fd = open(DEV_NODE, O_RDWR)) < 0) {
		printf("error: Can't open serial port %s!\n", DEV_NODE);
                return -1;
        }

	/*Init Uart for Um220*/
	um220_uart_init(um220_fd,&oldtio,&newtio);
	
	/*Set Um220 options*/
	printf("Please select modules of um220\n");
	printf("1.BD module\n");
	printf("2.GPS module\n");
	printf("3.BD+GPS module\n");
	if(scanf("%d",&command) != 1)
	{
		printf("error:input is wrong!\n");
	}
	switch(command)
	{
		case 1:
			memset(msg, 0, sizeof(msg));
			strcpy(msg,"$cfgsys,h01");
			if(write(um220_fd,msg,sizeof(msg)) < 0)
			printf("Failed to set BD modules!\n");
			break;
		case 2:
			memset(msg, 0, sizeof(msg));
			strcpy(msg,"$cfgsys,h10");
			if(write(um220_fd,msg,sizeof(msg)) < 0)
			printf("Failed to set GPS modules!\n");
			break;
		case 3:
			memset(msg, 0, sizeof(msg));
			strcpy(msg,"$cfgsys,h11");
			if(write(um220_fd,msg,sizeof(msg)) < 0)
			printf("Failed to set BD+GPS modules!\n");
			break;
		default:
			printf("Can't identify command,set BD+GPS modules!\n");
			memset(msg, 0, sizeof(msg));
			strcpy(msg,"$cfgsys,h11");
			if(write(um220_fd,msg,sizeof(msg)) < 0)
			printf("Failed to set BD+GPS modules!\n");
	}


	for(;;)
	{
	/*Read Data from Um220*/
	memset(newbuf, 0, 1024);
	nb = read(um220_fd, newbuf, MAX_PACKET_SIZE);
        if (nb == -1)
		{
                perror("read uart error");
		return -1;
		}
	if ((ret=strstr(newbuf, "$GNGGA")) != NULL)
		{
	/*Analysis Data*/
		parseData(ret);
		}
	sleep(1);
	}
	/*Recover Settings Of Serial Port*/
	tcsetattr(um220_fd,TCSANOW,&oldtio);
	/*Close Um220_fd*/
	close(um220_fd);

	return 0;
}

从串口设置、读取、并分析um220模块的数据