How to program linuxcnc tool changer

I have a 3 axis milling machine all wired up with Mesa 5i25, 7i76, 7i77 and 7i73 (for Pendant and keypad).
Tool changer has a carousel positioned by a stepper motor,  an "arm" controlled by several relays and a
clamp/unclamp motor controlled by several relays.  Z axis is moved to required height, rotates to correct
angular position and locks, arm swings in, tool unclamps, z raises to clearance height, carousel rotates to new tool etc...
I'm new to linuxcnc and don't know the best way to program this.  Do I need to compile a custom HAL component?
Or can I do it all from Custom Ladder?  Are there other better methods?  I apologize if there are some obvious
samples/instructions I missed in the doc.

Thanks,
Mike

Hi. Because you have to use the z axis to get the tool out and clear of the spindle, the easiest way is to remap the tool change M6 as well as Txx and use a g code subroutine to manage the tool change. 

Use carousel component to index the carousel. 

Henk

Take a look at the vmc_toolchange sample config. (you can run it from the configuration chooser, sim/axis/vismach/vmc_toolchange
It uses a remap of M6 that calles a G-code suproutine to raise the Z and operate the arm and clamp, and then uses the "carousel" HAL component to move the actual carousel to the right point.
Does your toolchanger carousel have any position feedback?

linuxcnc.org/docs/stable/html/man/man9/carousel.9.html

The sample config files can be viewed here, but if you open the sim on your PC then the files will also be copied into a folder in your linuxcnc/configs directory.