-----------------------------------------------------------------------
Cross compiler：arm-linux-gcc-4.5.4
Linux kernel version：linux-3.0
Development board：fl2440
Author:  Yuzhonghan <754270866@qq.com>

-----------------------------------------------------------------------

一：AT命令
    使用sim900发短信打电话之前，必须了解at命令怎么使用。下面是一些常用的命令
AT+CMGC   Send an SMS command（发出一条短消息命令）    
AT+CMGD   Delete SMS message（删除 SIM 卡内存的短消息）    
AT+CMGF   Select SMS message formate （选择短消息信息收发格式： 0-PDU;1-文本）
AT+CMGL   List SMS message from preferred store（列出 SIM 卡中的短消息
AT+CMGR   Read SMS message（读短消息）    
AT+CMGS   Send SMS message（发送短消息）    
AT+CMGW   Write SMS message to memory（向 SIM 内存中写入待发的短消息）
AT+CMSS   Send SMS message from storage（从 SIN |M 内存中发送短消息）
AT+CNMI   New SMS message indications（显示新收到的短消息）    
AT+CPMS   Preferred SMS message storage（选择短消息内存）    
AT+CSCA   SMS service center address（短消息中心地址）    
AT+CSCB   Select cell broadcast messages（选择蜂窝广播消息）   
AT+CSMP   Set SMS text mode parameters（设置短消息文本模式参数）
AT+CSMS   Select Message Service（选择短消息服务）
AT+CNMI=2,1,0,0,0          //设置收到新短信存于SIM卡中并发CMTI通知
+CMTI:”SM”,1           //收到了短信，自动弹出，其中1表示存在SIM中的序号
AT+CMGR=1             //读取短信，其中1要与上面序号对应
AT+CMGD=1             //删除短信，其中1为短信序号
ATD188********;       //拨打电话，后面一定要加‘；’
ATA //接听电话
ATH //挂断电话

在这博主所使用串口连接板子输入  microcom -s115200 /dev/ttyS1     这里我链接的串口是dev目录下的ttyS1，串口波特率是115200。

然后可以使用 AT指令测试。

PS:（这里可以根据自己的串口信息进行更改。）

以下是发送短信和拨打电话的C代码：

  1 /*********************************************************************************
  2  *      Copyright:  (C) 2016 Yuzhonghan<754270866@qq.com>
  3  *                  All rights reserved.
  4  *
  5  *       Filename:  gprs.c
  6  *    Description:  This file 
  7  *                 
  8  *        Version:  1.0.0(07/30/2016)
  9  *         Author:  Yuzhonghan <754270866@qq.com>
 10  *      ChangeLog:  1, Release initial version on "07/30/2016 05:23:56 PM"
 11  *                 
 12  ********************************************************************************/
 13 #include <sys/types.h>
 14 #include <sys/stat.h>
 15 #include <fcntl.h>
 16 #include<stdio.h>
 17 #include <stdlib.h>
 18 #include <unistd.h>
 19 #include <string.h>
 20 #include<termios.h>
 21 
 22 
 23 #define len_num 16
 24 #define len_mes 128
 25 
 26 struct message_info
 27 {
 28     char cnu[len_num];
 29     char pnu[len_num];
 30     char message[len_mes];
 31 };
 32 
 33 void serial_init(int fd) //初始化串口
 34 {
 35     struct termios options;
 36     tcgetattr(fd, &options);
 37     options.c_cflag |= (CLOCAL | CREAD);
 38     options.c_cflag &= ~CSIZE;
 39     options.c_cflag &= ~CRTSCTS;
 40     options.c_cflag |= CS8;
 41     options.c_cflag &= ~CSTOPB;
 42     options.c_iflag |= IGNPAR;
 43     options.c_oflag  = 0;
 44    options.c_lflag  = 0;
 45 
 46 
 47     cfsetispeed(&options, B115200); //根据自己的波特率进行相应更改
 48     cfsetospeed(&options, B115200);
 49     tcsetattr(fd, TCSANOW, &options);
 50 }
 51 
 52 
 53 int send(int fd,char *cmgf,char *cmgs,char *message) 
 54 {
 55     int nread;
 56     int nwrite;
 57     char buff[len_mes];
 58     char reply[len_mes];
 59 
 60 
 61     memset(buff,0,len_mes);
 62     strcpy(buff,"at\r");
 63     nwrite=write(fd,buff,strlen(buff));
 64     printf("nwrite=%d,%s\n",nwrite,buff);
 65 
 66 
 67     memset(reply,0,len_mes);
 68     sleep(1);
 69     nread=read(fd,reply,sizeof(reply));
 70     printf("nread=%d,%s\n",nread,reply);
 71 
 72 
 73     memset(buff,0,len_mes);
 74     strcpy(buff,"AT+CMGF=");
 75     strcat(buff,cmgf);
 76     strcat(buff,"\r");
 77     nwrite=write(fd,buff,strlen(buff));
 78     printf("nwrite=%d,%s\n",nwrite,buff);
 79 
 80     memset(reply,0,len_mes);
 81     sleep(1);
 82     nread=read(fd,reply,sizeof(reply));
 83     printf("nread=%d,%s\n",nread,reply);
 84 
 85     memset(buff,0,len_mes);
 86     strcpy(buff,"AT+CMGS=");
 87     strcat(buff,cmgs);
 88     strcat(buff,"\r");
 89     nwrite=write(fd,buff,strlen(buff));
 90     printf("nwrite=%d,%s\n",nwrite,buff);
 91 
 92     memset(reply,0,len_mes);
 93     sleep(1);
 94     nread=read(fd,reply,sizeof(reply));
 95     printf("nread=%d,%s\n",nread,reply);
 96 
 97     memset(buff,0,len_mes);
 98     strcpy(buff,message);
 99     nwrite=write(fd,buff,strlen(buff));
100     printf("nwrite=%d,%s\n",nwrite,buff);
101 
102     memset(reply,0,len_mes);
103     sleep(1);
104     nread=read(fd,reply,sizeof(reply));
105     printf("nread=%d,%s\n",nread,reply);
106 
107 }
108 
109 int send_message(int fd,struct message_info info)
110 {
111     getchar();
112     char cmgf[]="1";
113     int conter=0;
114     char cmgs[16]={'\0'};
115 
116     printf("Enter you number,please: \n");
117     fgets(info.pnu,(len_num-1),stdin);
118     while(strlen(info.pnu)!=12)
119     {
120         if(conter>=3)
121         {
122             printf("conter out!\n");
123             return -1;
124         }
125         printf("You should enter a 11 digit number! Again: \n");
126         fgets(info.pnu,(len_num-1),stdin);
127         conter++;
128     }
129 
130     printf("Please enter you want to send a message!\n");
131     fgets(info.message,(len_mes),stdin);
132     strcat(info.message,"\x1a");
133     strcat(cmgs,"\"");
134     strcat(cmgs,info.pnu);
135 
136     cmgs[12] =(char) {'\"'};
137 
138     send(fd,cmgf,cmgs,info.message);
139 
140 }
141 
142 
143 int call(int fd,char *atd)
144 {
145     int nread;
146     int nwrite;
147     char buff[len_mes];
148     char reply[len_mes];
149 
150     memset(buff,0,len_mes);
151     strcpy(buff,"at\r");
152     nwrite=write(fd,buff,strlen(buff));
153     printf("nwrite=%d,%s\n",nwrite,buff);
154 
155     memset(reply,0,len_mes);
156     sleep(1);
157     nread=read(fd,reply,sizeof(reply));
158     printf("nread=%d,%s\n",nread,reply);
159 
160 
161     memset(buff,0,len_mes);
162     strcpy(buff,"atd");
163     strcat(buff,atd);
164     strcat(buff,"\r");
165     nwrite=write(fd,buff,strlen(buff));
166     printf("nwrite=%d,%s\n",nwrite,buff);
167 
168     memset(reply,0,len_mes);
169     sleep(1);
170     nread=read(fd,reply,sizeof(reply));
171     printf("nread=%d,%s\n",nread,reply);
172 
173 
174 }
175 
176 int call_phone(int fd,struct message_info info)
177 {
178     getchar();
179     int conter=0;
180     char atd[16]={'\0'};
181 
182     printf("Please enter the number you need to dial: \n");
183     fgets(info.pnu,(len_num-1),stdin);
184     while(strlen(info.pnu)!=12)
185     {
186         if(conter>=3)
187         {
188             printf("conter out!\n");
189             return -1;
190 
191         }
192          printf("You should enter a 11 digit number! Again: \n");
193           fgets(info.pnu,(len_num-1),stdin);
194           conter++;
195     }
196     strcat(atd,info.pnu);
197     atd[11]=(char){';'};
198 
199     call(fd,atd);
200 }
201 
202 
203 
204 int main(int argc, char **argv)
205 {
206     int fd;
207     struct message_info info;
208     char choice;
209 
210     fd=open("/dev/ttyS1", O_RDWR|O_NOCTTY|O_NDELAY);
211     if(fd<0)
212     {
213         perror("Can't open the serial port!\n");
214     }
215 
216     serial_init(fd);
217     printf("\n------------------------------------\n");
218     printf("Welcome to GPRS!\n");
219     printf("\n------------------------------------\n");
220     printf("Please input you select:\n");
221     printf("1.Send a Enlish message.\n ");
222     printf("2.Call phone.\n");
223     printf("3.Thinking fou using\n");
224     choice = getchar();
225     switch(choice)
226     {
227         case '1':send_message(fd,info);
228                  break;
229         case '2':call_phone(fd,info);
230                  break;
231         case '3':break;
232         default : break;
233     }
234 
235 
236 
237 
238     close(fd);
239     return 0;
240 }