Modem AT commands from C

[Jim Hansen]

I want to get the result of AT command in a C program.

I open /dev/ttyUSB3 or 5 (on an H4 radio) and sets the serial port to 230400, 8N1, send an AT command and read a response. I don’t get any errors, but I get no output or “nERRORnn” back.

Is there another way to get an AT command’s response? Microcom has some issue with stdout, I hear.

Or, how do I know the port settings to use the port directly?

[Bryan Tran]

Hi Jim,

1. The correct port for the H4 is: /dev/ttyUSB3 and /dev/ttyUSB4.

http://www.multitech.net/developer/products/multiconnect-ocg/hardware/multiconnect-ocg-d/accessing-hardware-interfaces/

2. As a test, would you please ssh into the CDP device and issue the following command:

microcom /dev/ttyUSB3 -s 115200[Enter]

AT[Enter]

Do you get any response ?

*Note: If you do not see what you are typing, try: ATE1[Enter]

If you do get response on the above command, then it likely there is something in your C program.

Regards,

BT

[Jim Hansen]

I did get a response:

“ERROR”

then another AT command and “OK”

I assume that something’s wrong with the code/port setup. I intermittently get “ERROR” or 0 bytes.

How do I know the correct settings for this port?

Is it documented?

I’m now using 115200 baud.

[Bryan Tran]

Hi Jim,

Would you pls reboot your CDP and then ssh back into your CDP and type the following commands, post your output.

microcom /dev/ttyUSB3[Enter]

AT[Enter]

ATI[Enter]

AT+CSQ[Enter]

AT+CREG?[Enter]

AT+CPIN?[Enter]

I am not very sure why you would get an “Error” message response after typed in AT[enter].

The USB port will ignored the serial baud rate settings.

Regards,

BT

[Jim Hansen]

Hi,

After reboot, get the expected output

OK

Manufacturer: Sierra Wireless, Incorporated

Model: MC8790V

Revision: K2_0_7_24BAP C:/WS/FW/K2_0_7_24BAP/MSM6290/SRC 2010/02/09 00:19:18

IMEI: 012376000067082

IMEI SV: 15

FSN: C681542057310

3GPP Release 5

+GCAP: +CGSM,+DS,+ES

OK

+CSQ: 1,99

OK

etc.

After I run my program, I do this again and the first time AT returns ERROR, then its ok.

If USB doesn’t need baud rate, are there other settings it does or doesn’t need? My code looks a lot like the termios part of

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

Jim

[Bryan Tran]

Hi Jim,

Take a look at this sms-utils code and may by take out the serial port part http://git.multitech.net/cgi-bin/cgit.cgi.

Regards,

BT

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