I am trying to run a python app which controls sevomotors. There is no handshaking, just a bit bang from pin 3 of the DB9 straight into a PIC.

There is nothing showing on the oscilloscope: it's just flatlining.
I do a dmesg grep | tty and get nothing at all showing.

I've done:
sudo setserial ttyS0 autoconfig
mknod -m 660 /dev/ttyS0 c 4 64 # base address 0x03f8
/sbin/MAKEDEV -v ttyS0
Still nothing shows up on a dmesg

Until I run gtkterm. At which point I can press keys to my hearts content and the scope shows me pretty square waves.
But as soon as I close gtkterm, I've lost ttyS0.

This app apparently works for other people, but that doesn't help me a lot.

I'm running Mint Katya 2.6.38-13 on a Dell Latitude D430, connected to a docking station with a COM1 serial DB9 connector attached, and the BIOS is happy with COM1 active (as proved by gtkterm)

The app is attached as a text file.

So how do I get the computer to permanently see ttyS0, or what would I change in the app so that it will work?
I have python-serial installed, just don't really know what else do.

Anyone got any ideas?

Thank you in anticipation..


Well, at least you know that the port does work. Sorry but I'm not a Python programmer, so I can't tell you if there is a problem with the code. In any case, you should NOT have needed to create the device node for /dev/ttyS0 - that should by default be auto-configured by the OS for the COM1 port on your system. Do make sure (again) that the COM ports are enabled in the BIOS.

FWIW, I've used a lot of serial ports with a lot of Linux systems, and never saw this sort of problem. :-(

Do make sure (again) that the COM ports are enabled in the BIOS.

No problem.
I can echo directly to the chip just by "echo blah blah > ttyS0", which means ttyS0 is now permanently seen, so the port works fine, just something amiss between Mint and Python.