Coherent Diagnostics


I had to get some diagnostic information from a Coherent laser. It's super easy if you connect via USB on an Ubuntu machine.

First, install minicom:

sudo apt install minicom

Now you need to find the name of the device. Run

dmesg | grep tty

The output will look something like this:

$ dmesg | grep tty
[    0.000000] console [tty0] enabled
[26890.843225] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB0

Unplug the USB and plug it back in again, and rerun

dmesg | grep tty

You'll see additional messages about something getting disconnected and attached, similar to this:

$ dmesg | grep tty
[    0.000000] console [tty0] enabled
[26890.843225] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB0
[27005.835517] ftdi_sio ttyUSB0: FTDI USB Serial Device converter now disconnected from ttyUSB0
[27057.953214] usb 1-2: FTDI USB Serial Device converter now attached to ttyUSB0

In this example, the device name is ttyUSB0. Now run

sudo minicom -s

and select “Serial port setup”. Type A (no enter key, it will automatically move your cursor) and change the serial device to

/dev/ttyUSB0

or whatever your device name is. It will have /dev/ in front of it no matter what.

Now type E to set up the other parameters. Type B to lower the speed (or A to raise it) to 19200. It says the current speed at the top. Type Q to set the parity and stop bits. When you're done, it should say at the top:

Current: 19200 8N1

If it does, press enter. Now choose Exit (not Exit from Minicom). You'll be taken to a terminal where you're now connected. You can start issuing commands, which all start with a question mark. Try:

?STA

It should return some sort of number or something. The rest of the commands should be saved here, or you can ask Coherent for them.