Procedure to issue AT commands from a C program.

[JM K]

Hi,

I am working with an EV2 CDP Unit. I am trying to write a small application that accepts a message in the form of a text file (gedit) and sends an sms to a custom phone number also entered by the user. I am confused as how to access the minicom interface via a C program. Is there any other way AT commands can be issued at the terminal after logging in to the device at run time through a C program? Any suggestions would be very much appreciated. Thank you very much and have a great day.

Best Regards,

JM

[Jesse Gilles]

JM,

You don’t need to use minicom to talk to the modem. Linux treats the serial port for the modem (/dev/ttyUSB0) as a file, so you can do reads and writes as if it were a regular file in your C application. There are also C calls you can make to configure the serial port (baud rate, etc).

Here is a page that has some examples, take a look at the section labeled “termios”.

http://en.wikibooks.org/wiki/Serial_Programming/Serial_Linux

You are also free to look at and use the source code for the sms-utils application, which is written in C.

http://git.multitech.net/

Jesse

[JM K]

Hi Jesse,

thank you very much for the reply. I wrote a small C program that would just open the ‘file’, ttyUSB0 and send out an SMS to a phone number using the AT commands. I am however getting a Segmentation fault when I try to open the file ttyUSB0 and write an AT command to it. Here is my program:

void main()

{

FILE *fileptr;

fileptr = fopen(” /dev/ttyUSB0 :,”a”);

puts(“AT!SSMS=0,xxxxxxxx,0,yyyyyyyyyy”); /* xxxxxxxxx is the phone number and yyyyyyyyy is the message */

fclose(fileptr);

}

I would appreciate it if you could let me know where my program went wrong. Thank you very much and have a great day.

Best Regards,

JM

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