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