Back or front tool

Thank you but no difference Andy
Pin 16 stays low on both M3 and M4

I think as a sanity check I would see if it is a hardware issue. As an experiment try swapping the LPT pins around.


Example:
net spindle-ccw spindle.0.reverse => parport.0.pin-17-out

Also swap 16 around
And have a look at what is going on at 17

Open halmeter and look if the spindle.0.reverse pin and the spindle-ccw signal are doing the right things.

Also note that you need a non-zero spindle speed set too. So M4 S10 to test.

Right !
So I am in Gmoccapy screen and using (onscreen) spindle forward, stop , and reverse buttons . Also watching LEDs in halshow(watch)
So I select spindle forward
Pin 17 shows illuminated Led, spindle runs ccw and selected speed shows 300.
spindle stop causes both Leds to go out spindle stops
Spindle reverse brings on both Leds, spindle still runs ccw
At Bob Led illuminated yellow corresponds with 5v at pin ( red gives 0v)
At this stage in Hal      net spindle-on => parport .0.pin-17-out
And            net spindle-ccw spindle.0.reverse => parport.0.pin-16-out



So In hal file I transpose 16 into spindle "on" command and 17 into spindle "reverse" command .

Now repeating the process:-
spindle start clockwise button does not cause spindle to run at all but pin 16 Led illuminates
Spindle stop both Leds go red
Spindle reverse button illuminates both leds and both pins go to 5V
Spindle still  runs ccw and speed indicator shows minus 300

With regard to the hardware  , if I ground the signal wire to my relay board  the  relay indicator lamp comes on and my reversing relay operates so I am happy that is operating as it should !

So folks . does this tell you anything?

Might it be an Idea for me to try this with a new stepconfig calling for spindle forward on pin 17 and reverse on 16

What does it take to make the spindle turn in reverse? Does any combination of the outputs make the spindle turn backwards?

Start LinuxCNC and set the spindle running at 300 rpm.

Now, open a terminal window.

You can now control the pins manually, to see what happens

Will run through all the combinations. If none of them result in the spindle turning backwards then the problem is in your hardware, not the HAL.

When you have finished experimenting:

You will need to re-start LinuxCNC to get back to Linuxcnc having control of the spindle.

No eBay APP ID and/or Cert ID defined in Kunena configurationMy spindle motor is DC so reversing the polarity reverses the spindle . I have done this with a simple DPCO reversing switch.
I have now replaced this with a reversing relay which in turn is operated by a relay on a small multi board 

This relay operates when an input signal is grounded and I have proved this

I will try the procedure you outline and will report back.

Thanks again