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I'm pretty sure Tommy would disagree with that, personally I've never had any issues with HP gear, even the ancient server I was running 24/7.
I'd say that there are quite a few HP machines running Linuxcnc that never give any issues.

Yeah, a manual MPG shouldn't require reading at the same rate as would be required for spindle encoder.
Just remember that the RPi io is only 3.3v tolerant, so a way of translating the MPG signal voltage and protecting the RPi io from noise.
The 74lvc series are 3.3v devices that are 5v tolerant on their inputs.

so your saying take the Pi GPIO and put it on a server thread not on a realtime thread?

Some do some don't, you'll need to check the data sheets.
The role of the diode is to protect the driving circuit from the reverse voltage generated from the collapse of the magnetic coil. No flyback will eventually cause component failure, a far bigger issue than EMI.
I'd take PCW's advice.
Another thing I would look at is the routing of your wiring and ensuring physical seperation of control and AC, if you haven't already taken care of this issue.
If you do use optos make sure that the input side and output side are powered by seperate PSUs and the ground are not connected, it aggravates me when I see opto circuits with the input and output sides connected to a common ground.

The issue here is that the relays are switching a 120VAC solenoid.

Because the solenoid is an inductive load, this will cause massive EMI unless
there is contact arc suppression across the relay contacts. This can be done
with a bipolar TVS diode, a MOV or an RC arc suppressor.

Shouldn't be an issue, as all you you are doing is adding another function, servo thread should be ok for MPG.
Give it a go and see what happens.

Thanks for this Chris, especially pleased to seeing the lathe part getting TLC 

I switched to develop branch and did the uninstall and reinstall, went like a charm!
I noticed that unlike Gmoccapy issuing G43 doesn't update the active G codes, G49 remains, is that expected?

Now for the newby bit, does tool touch off only work with an active (or passive) probe, so I need a probe wired in and configured to set tool offsets?
Or is this a G49 artifact from above?

Thanks again for this awesome interface and your work!

Then you need arc suppressors across the relay contacts.

Possibly something like this:

www.digikey.com/en/products/detail/bourn...OV-10D201KTR/2408223

Note that it looks like the relays have their own drivers, so the 7I95T does not need
any flyback diodes.

They are 120v ac so unfortunately can't use flyback diode.

The solenoids are ac 120v. So I can't use a flyback diode on them. Its the relay coil that is giving me spikes going back to the mesa 7i95t. So I need to stop that.

Yes, as tommylight says, the solenoids need flyback diodes as well as the relays.
( or if they are AC solenoids the relays need arc suppressors )

Do the solenoids draw more than 2A DC?  If not, they can be driven directly from the 7I95T
 

Thanks. I have a load of 1n4148s the problem is between which pair as the relay board has two grounds and one positive. One ground is from the psu and the other is from the ssr on the mesa board.

I have tied going from the psu positive to the mesa ground pin and it hasn't stopped the emi.

Your "usually......" is for power supplies, not solenoids and relays, very confusing info on the net, so better ask here.
The diodes musty be added to solenoids in parallel with their winding and as close to the winding terminals as possible, each solenoid must have it's diode, use 1N4007 or 1N4008 as are very cheap and easily found.
For bigger solenoids use 1N5407 or 1N5408.
For simplicity, the only thing to take care is the diode side with the line across must be wired to positive.

Hi peeps,

So I have a mesa 7i95t and I'm using two of the ssr outputs to operate a relay board that in turn operates some solenoids.

What i am experiencing is. Occasionally when the relays are opened and closed quickly I'm getting some EMI when the coil collapses causing my monitor to turn off for a second. and the occasional estop.
I know I need to add in some flyback diodes to stop this. But......where do I put them? Usually you would go across the positive and ground. But my relay board has 5 channels. So it has a main positive and ground
 then a separate ground for each channel that comes from the 7i95t output pin. Do I put the diode across the positive and signal from the 7i95t or across the positive and relay ground? I will attach a pic of the relay boards and a very bad sketch of what i mean.


Thanks in advance    

thanks Russell for the inspiration

github.com/multigcs/riocore/tree/dev/riocore/plugins/riosub

but it will be a long time before it works properly.