7i76 spindle control

@rodw I'm not sure that is the case, as last time I used the mycnc board for spindle control, and I checked it now &it has two relays, one for enable and one for direction on it and four wires off to the parport, gnd, step, enable and dir.
I pulled my old hal file and in the gearchange component it reverses by changing the dir pin state and these are the only lines relating to rotation direction. ;-

net spindle-cw <= stepgen.4.dir => parport.1.pin-17-out
net spindle-cw => parport.1.pin-17-out

I could be wrong though, I thought last time that my drivers enable pin was held high in use and that turned out to be wrong. If I add the relay I'll just be back to how I had it before minus the enable relay and board to supply analog voltages and I can port the old config to new pin names.

Typically when a 7I76 is used with drives that have only FWD/REV inputs
(and cannot be reprogrammed for DIR/ENA), you can use a single SPDT relay
to steer the enable signal to FWD or REV depending on the state of DIR

So:

+24V --> RELAY_COIL+
RELAY_COIL- --> DIR+
DIR- --> GND

ENA+ --> RELAY_COM
ENA- --> GND

RELAY_NC --> FOR
RELAY_NO --> REV

This assumes the VFD inputs are active low.
The relay needs a flyback diode.

Thanks all, good point on the flyback diode's for coil switched relays,
I should have said with a ssr rather than relay, as ordered some on a din rail mount so when they arrive I'll wire them in for all of my output switched functions as I can avoid using a flyback diode, and they're mostly more reliable.

Ended up buying a bank of din rail opto isolated relays, and allocated #1 to spindle direction as described, and the rest to suds/mist other duties and now everything is working as it should be.

Glad to hear the OP is sorted. There is another path that I went down which is to write your own HAL component to manage the logic - if I remember when I'm home from work I can post that if there's interest.