Reversing axes direction with external step generator

I have been using Linuxcnc with parallel port stepper drives for many years, and now just out of interest I am trying the esp32 ethernet step generator
here  github.com/jzolee/HAL2UDP as I believe a few other people here have done also.

It is basically working, I can jog ok but the axes directions are reversed. Can this be corrected in the hal or ini file?
I tried inverting SCALE in the ini file but then the machine refuses to move at all and I think the stepper drives were not even enabled after doing this.
I have become a bit blase about setting up parallel port systems but this has taken me right back to day 1 of config confusion.

 

I don't want to faff with the machine. I have several machines, including this one, set up so that I can just plug a parallel port cable into them with Linuxcnc or grbl or whatever on the other end of the cable and they all operate the same. I don't want one odd machine.

I haven't used windows since 1998  apart from one machine (not this one) that still uses proprietary code on a 24 year old win98 computer

When daylight arrives here I will go back out to the shop and capture the network data packets to try and figure out what is going on.

Like I said this is just out of interest, I recently retired, all the big machines have gone, I only have small desktop machines and a lot of time. 

I just had another go at this and I can see why the steppers did not enable before.
If I set scale in the ini file to a positive value the machine homes the Z axis perfectly to the wrong end of its travel.
When I set scale to a negative value I get an instant 'joint following error' on the axis.
I am on a twin monitor system and the message was popping up right on the corner join between the two monitors and I didn't see it before.
I'm trying all this on a laptop for the first time and have now started getting realtime error messages so it is time to abandon this computer and try one of the others I have lying around.