To get a list of all the Mesa pins make sure field power is on then open
a terminal and do the following. ~$ and halcmd: are not to be typed they
are the terminal prompts. If you add a config to the hm2_pci line it will
change the pins that show up.

from a terminal: linuxcnc /home/tom/linuxcnc/configs/Sherline/sherline.ini
from another terminal: halcmd show pin
from another terminal: halcmd show

or

~$ halrun
halcmd: loadrt hostmot2
halcmd: loadrt hm2_pci
halcmd: show pin > pins.txt