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I'm working on BeagleBone Black (Debian running on it) and I have connected a 3G USB dongle (Huawei E173u-2) with it for GPRS and sending SMS.

Now I am facing a problem when I am booting my board (dongle attached). I can access GPRS service, but cannot send SMS at the same time (using AT commands from MINICOM). If GPRS service is on and I am sending AT command to 3G USB dongle, I am getting a reply

Service Temporarily Unavailable.

If I run command on terminal

ifdown gprs(service name)

ie. GPRS service is OFF, now I am able to send SMS.

In SMS mode if I run command in terminal

ifup gprs(service name)

I am not able to get GPRS connection until I close MINICOM connection used to send AT commands to 3G USB Dongle.

As I have searched about this issue, I have read a blog which says each service locks the port at which dongle is connected. Until service releases the port, other service cannot access the same port.

I have tried this on Windows and found that I can access both services at the same time.

What is the actual cause of this issue and how to resolve it?

Saad Rafey
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  • Last time I used GPRS and SMS was on a single-tasking single-user OS, and both were indeed not concurrent. Are you sure the Windows driver isn't *simulating* concurrency by turning off GPRS in the background while you send an SMS? Try this out on Windows by sending 20 SMS's while sending GPRS data and report back. I'm betting your throughput on GPRS goes to 0 while you're sending the SMSes... – Fabby Aug 01 '15 at 14:33

1 Answers1

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Open /etc/ppp/options file and go to line number 65, just comment it.

Line 65 is:

lock

Change it to

#lock

And reboot.

Saad Rafey
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