View Full Version : [SOLVED] Non-intrusive access to serial CDR status

February 23rd, 2011, 07:58 PM
How can I determine whether CDR is high on a serial port, without disturbing any current access to the device? Any way to tell by looking in /sys or /proc? I'd prefer to have a non-compiled solution, if possible.

I attempted to use pyserial's serial.getCD(). It works correctly, but the open() call appears to disturb the existing modem connection somehow, even if I don't call close(). I'm not sure why, but I lose the modem link, even though CDR remains high.

Background: I'm sharing two outbound-only modem lines between several virtual machines, and I need to determine whether a modem is in use prior to switching it to the VM that is requesting it.

March 18th, 2011, 05:33 AM
solution: statserial