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I am running a USB cell modem via PPP in Embedded Linux. I can use AT commands via minicom to connect to the modem and interrogate the signal strength (AT+CSQ) when the PPP connection is not active. However, when it's active, this is not possible.

Is there any way to retrieve the signal strength from a PPP connected USB cell modem while the PPP connection is being used? I am open to an API or any other method available.

kittyhawk
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  • I've always wanted to do the same thing but never got much farther. I'd thought of installing something to trace the USB operations that were performed when using the device in Windows. Perhaps that would give some insight into how it's done there? – MikeK Mar 03 '11 at 04:03
  • I havn't make it works yet, but this guy have found the answer : [stackoverflow.com/questions/17322154/how-to-get-3g-modem-signal-strength-in-c-linux](http://stackoverflow.com/questions/17322154/how-to-get-3g-modem-signal-strength-in-c-linux) – MokaT Sep 02 '15 at 13:51
  • Great link, but won't work in a headless environment. – Moonchild Mar 11 '16 at 09:55

2 Answers2

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I don't have a umw190, but the Linux driver for the modem should have more than one ttyACM character device available. Use one for PPP and the other for AT+CSQ. Check dmesg for cdc_acm to see.

If your embedded device has udev then both devices should automagically appear in /dev. If not you'll have to mknod more. Off the top of my head major number is 166 for cdc_acm.

Roderick Taylor
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What does the physical setup look like? 1. Are you using a modem that is on a board designed/printed by the same company as your SBC? 2. Is it connected via something like PC104 serial or USB? 3. What specific modem are you using?

kmarks2
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  • It's a Verizon UMW190 USB modem connected to the board's external USB port. Here is the board: http://www.embeddedarm.com/products/board-detail.php?product=ts-7800 – kittyhawk Nov 04 '10 at 13:42