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Old 05-08-2016, 04:40 PM   #1
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Registered: Aug 2015
Location: WNY state
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Unhappy Can't get USR 56k external serial modem working in Debian 8.4

I am having an issue with my USRobotics 56k external serial modem in Debian jessie. I am trying to communicate with the modem with minicom and gnome-ppp. However, I have had no luck trying to do so. When in gnome-ppp setup, I click "detect modem" and my modem is set to /dev/ttyS1 (as it is plugged into the second serial port on the computer) and no modem is detected. If I simply try to dial the number anyway, It will give up and say modem not responding after a few seconds. I have looked in the bios on this machine for the port settings and I had them set to default settings, and now I am trying them on auto. They still are reporting the same settings under setserial. The settings for ttyS0 are UART: 16550A Port: 0x03f8 IRQ:4. The settings for ttyS1 (the port i have the modem connected to) are UART: 16550A Port: 0x02f8 IRQ:3. I am stumped as to what I should do next. Also I should mention that when I use minicom, it used to start up and initialize the modem and even though I wasn't online, it would say otherwise and to hang up. If I set "Modem Has DCD line" in minicoms settings to "no" then I hear a fuzzy-sounding dialtone for a second or two and then nothing. If I let it keep going, it just will time out and try again. I hope you guys can help me.

BTW, my system specs are:
AMD Athlon 64 4000+
1gb DDR
250gb IDE HDD
Nvidia Quadro FX 1700
EVGA Socket 939 motherboard

Also the model number of the modem I'm using is a USrobotics 5686 external serial dial up modem. Thanks!
Old 05-08-2016, 06:00 PM   #2
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Just to start from the beginning, to test the MODEM I would setup minicom to use 115200 baud, 8 data bits, 1 stop bit, no parity and use both hardware and software flow control. Starting minicom with the -s option will bring up the setup menu.

If everything works the MODEM should echo back characters when typed on the keyboard and you can enter the command at&v to see the MODEM's configuration pages. If that does not work then there is something wrong with your configuration, the serial port or the MODEM. I might try switching serial ports just to make sure I am using the correct port or to make sure it isn't bad.

To test the serial port and cable with minicom set hardware flow to none and jumper pins 2-3 together on the connector that connects to the MODEM. Serial port settings other then hardware flow do not matter and you should be able to see characters as you type. You can build a serial jumper test connector if desired. If that does not work then you may have a serial port or cable problem. You can remove the cable and jumper the pins at the computer itself and repeat the test.

The assumption is that you are using root and/or all the permissions/groups are configured correctly for your user.
Old 05-09-2016, 06:53 AM   #3
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Registered: Aug 2015
Location: WNY state
Distribution: Manjaro i3
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Thanks, I will try that when I get home. I have my account in the correct groups as well. I did have software flow control disabled by default. I will get back to you soon.


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