Found this post,  sounds similar to what you need.

Hello All,

New to the forum and first of all would like to thank you for the valuable information you guys post, it has helped so much me moving ahead with my build. id appreciate your help with my issue where it cannot activate the thc even when all the settings (that i know of) have been properly adjusted. first my setup:
-LinuxCNC QTPlasmac table
-Rpi5 with image LinuxCNC 2.9.8 Raspberry Pi 4/5 OS based on Debian Trixie
-Mesa 7176s over ethernet
-THCAD2 + 3M resistor array enclosed near the plasma source, F+/F- routed to mesaboard encoder input A with shielded microphone cable grounded at control side, also used a more simple twisted pair for testing.
-Used Pnconf for setting thcad2 trimming and ratio
Tested for correct voltage measuring for example, hooked a power supply from 39 to 56 volts and Main screen voltage readings coincide very accurately to multimeter reading.
-Flaring 65 plasma source with no cnc interface. (HF piercing) voltage probing connected to torch (-) and clamp (+) leads.
-For testing im using a straight line of 100mm at full speed so thc is not affected by speed reduction  (tested from 400 to 1800 mm/min)
-THC is enabled
-Mode 0 is used so arc ok is derived from voltage readings
-setup plasmac.arc_lost_delay =.3 as was having some issues for getting it to start cutting due to initial spike/valley.

I took the follwing HALSCOPE trace where:

 

1)torch on triggers,
2)probe voltage goes to 260 for piercing, then falls, then recovers to around 94v
3)Arc OK signal goes to true
4)Pierce delay elapses
5)Movement starts
6)THC active never goes up and of course  no correction

as Far as I can see voltage is "stable" once cut starts and there is no variation that could lead to deactivation as the tresholds are LOW=39 HIGH 990 (for testing purposes), samples 10 and threshold voltage 10.

has anyone had this issue or any lead on what to look at?

Create a (physical)button, so you can read pin signal, and if 0 do... if 1 do...?
There is no parameter screen where you can watch/change parameters, would be nice do.

Could you elaborate what you want to change while milling?
Only thing i could think of is change off depth?

Maybe an electrical issue, if you do a  very slow commanded move
do the parallel port inputs pins used for reading the quadrature encoders
toggle as they should?  (in halscope)

That sounds pretty awesome. Does it interface similar to how the MESA cards do, with a HAL file and firmware that is written to the card?

Would you share the hardware info for the X1 connector, so I can design a card that could plug in? (I can probably buy a main card from you as soon as you're ready to sell it, and I may be able to be helpful with the firmware but I've not done FPGA programming in over 20 years)

Is there any practical method to input a variable while a g-code program is running? For example Pause, Request input, Resume, and then use that input.

Currently using 2.8.4 with the Axis interface.

I know multiple ways to change variables when a program is not running, but I have never seen any method for temporarily modifying a running program.

This would allow a single program to process workpieces with different sizes, for example.

I understand this could be dangerous, stupid, or worse. Not planning to be a pioneer.

I searched the forum and the documentation, and I could not find any mention of this topic.

Gene

Ok, thanks PCW.

Thanks guys. I will see if I find time to try a 2.9.8 install on a second drive (I have an SSD laying around awaiting that I do the same task on the Maho, which is still on 2.7). I am not using any Python or glade code, other than Andy's Lathe Macros.

I might start off trying to halcompile the most current version of carousel.comp
Cheers,
Mark

Here are my updated files that work (for now, until I change them again)

 

Was ginge den vom rpi4?

Ich hab ein rpi4 mit 7i92 an einer emco vmc100.
Läuft super.
Latenz ist aber so lala.. daher wollte ich den für nen tischaufbau nutzen km sachen zu erproben.

An die vmc100 kommt n optiplex 3050m.

Halt stop, zurück

den TangNano9K kann man nicht vom RPI4 aus programmieren, dafür braucht man einen PC.

zum rumspielen ist denke ich, ist der TangNano9k ein guter einstieg,
im prinzip geht es auch günstiger, ber dann ist man extrem limitiert.

Aber es kommt immer drauf an was du machen möchtest, es sind halt nur dev-boards.

Ahaaa i have laying a 7c81... i use on my rpi4 a 7i92.

Other question

What is the cheapest fpga with which i can start? Can you recommand...

Ach qas laber ich hier auf englisch...
Was ist deiner meinung nach der günstigste fpga zum starten?
Stm32 black und bluepill hab ich... auch n radpberry pico usw..

Danke dir

nope, moving way slower than by hand. It´s not getting any position change at all, even with super slow acceleration/velocity

maybe the move is to fast or the resolution of the encoder too high for parport