I am running Debian on an Embedded system and am trying to use minicom to periodically get the signal strength of my USB EVDO modem using the AT+CSQ command.

When the modem is not connected, I can simply use minicom to connect to the port and execute this command. However, when the modem connects to the network, commands in minicom no longer work (ie. nothing happens or is echoed to the screen).

Any assistance with obtaining the signal strength while connected is appreciated.


There are two ways to achive this:

If your mobile device provides more than one serial port (/dev/ttyUSB1 or /dev/ttyACM1 for example) you could use this one to query the signal level.

if you only have one serial, you have to put more effort into it and use a GSM 7.10 Serial Port Multiplexing. A implementation can be found at http://git.freesmartphone.org/?p=gsm0710muxd.git;a=summary

There is also a Debian package in Squeeze for gsm0710muxd,m see http://packages.debian.org/source/squeeze/fso-gsm0710muxd

hth, cheerio Steve

  • My USB modem is connected to /dev/ttyACM0 on my system. The system also has ttyS0 and ttyS1 but I assume those are for the RS-232 connections. The modem only has one port. I'm not sure I follow your logic about having multiple ports. – kittyhawk Aug 18 '10 at 19:42
  • Many GSM USB Modems like Option GT380 or Sierra Wireless MC8790 provides more than one serial line. Consider to use a device which provides more than one serial interface, or use the multiplexing. – Lairsdragon Aug 18 '10 at 20:10

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