New to linuxcnc, basic question for DRO modes with encoded handwheels

Hi,I'm in the early stages of researching a conversion for my PM-25 mill to use stepper motors and encoders, with the goal of creating an easy-to-use system for both manual and CNC operation. Ideally, it will be a 50/50 split between DRO mode and running G-code from my CAM software.

I have experience with 2.5 and 3-axis Southwest/Prototrak systems and really enjoy using X/Y DRO mode for quick manual jobs—especially for things like reworking a part on the fly with handwheels.

Now, for my question: I came across Probe Basic, which looks like a good fit for my needs, but is it possible to have a DRO mode where external encoders on the X and Y axes feed into LinuxCNC, move the stepper motors, and display the position on the Probe Basic screen?

In short:

• Enter DRO mode.
• Turn a custom encoder on the X axis and Y axis (e.g., 100 steps maybe even a fine or course option? ).
• The table moves accordingly, and LinuxCNC tracks the position.
• If needed, I can zero out the position, similar to how old MX2 or K3 Prototraks work.

Would this kind of setup be possible? Im ok with EE and Software, can build a PCB but rather look for some options first. Thanks!

Are you asking for hand wheel inputs with encoders to "manually" move your stepmotors or are you asking about adding encoder feedback to your axis to feed back the position, if your powered off axis are moved by hand?

Both are possible, and technically would require approximately the same hardware. But the handwheel option would require less strict timing requirements because missing an encoder step there is less critical.

Yes --> "hand wheel inputs with encoders to "manually" move your stepmotors" via linuxcnc. and if it misses a step or two from my hand_encoder to the linuxcnc/DRO, no big deal as me (the human) will stop turning when the DRO shows the number im after. I get there may be backlash depending on the ball leads I use. question for another post. Unless its a deal breaker now.

for this one --> "adding encoder feedback to your axis to feed back the position" my plan is to use steppers with motor_encoders for feedback to the stepper driver. So closed loop driver-to-stepper but open loop to Linuxcnc to driver. I may be off here.

so silly question, but if i were to turn the X and Y at the same time, it will do a 45deg ish travel? they are both non blocking?

What kind of io hardware are you using? Parallel port, Mesa cards, or something else? For example many Mesa io boards offer settings to use some of the regular inputs as hand wheel encoder inputs.

The good news is im open to hardware options!

PC and Parallel - I have an older PC with the Parallel port that i could use... (I read that a USB to 25pin is no good for latency, so not going that route, this has the port!) 

Mesa - I know of it. seems good if the setup is more straightforward. Looks like they run about $100 to $300. Do you happen to know a PN or feature so i can look that up?

Cheap stuff maybe just to test on? there is also some USB styles... but i dont think they place nice with Linuxcnc?
www.amazon.com/Controller-100Khz-Breakou...08BJTB1GQ/ref=sr_1_6

USB to parallel port not supported at all, don't an option.
Any other USB motion control are not supported.
All supported Mesa boards can be found on their website. You can also browse the forum to see what boards are popular at the moment.
For the DIY route Ollie's Linuxcnc- RIO project is fantastic, well supported and in active development as is Scott's Remora Project.
I've also been working on a setup that uses FPGA Dev board available via AliExpress that runs Mesa's hostmot2 firmware, ATM it only uses SPI interface for the Raspberry Pi or EPP for the PC platform, tho I'm currently working on an ethernet plugin board.
In all honesty if it wasn't so expensive to get items from the US to Australia I'd go with Mesa in a heartbeat. What board just requires at little time researching, coming up with a couple of choices then asking a few questions, the 7i76 boards pretty much have it all.

Some of Mesa's cards have dedicated inputs for hand-wheel encoders.
But this is so slow counting that you can use normal pins and the encoder component to get the hand-wheels inputs.
"normal pins" means parallel port pins, mesa input pins or some other digital io in pin.
linuxcnc.org/docs/html/man/man9/encoder.9.html

Nice! that link is helpful. So to summarize the next steps for a very basic test setup with no mill: 

• Ill need a older PC with a native parrellport
• Load a copy of linuxcnc and Probebasic (ill follow some youtube) 
•  parrellport cable to breakout board (i can prob find soemthing basic on amazon, if that goes well later upgrade to Mesa)Seem thats incorrect and need something a bit more robust like a "7I96 STEP/IO Step & dir plus I/O card"
  • I/O OUT  --> to drive steppers via commercial driver like a stepper online DM542T
  • I/O IN --> to read my two X and Y encoders. These are typically two pins so it can sens direction, so 4 needed Xa Xb and Ya Yb from the encoders. maybe even a Za and Zb if i want to move the Z axis.    
  • Some config file or other tweak to get the "encoder.N.counter-mode" to work from that link...
    
    Probably a little stuck on the last bullet. Not sure what to google. Am i on the right track?
    Its my first post so sorry if this is old news. 
    
    

The Linuxcnc docs have some good information on setting up hand wheel encdoers (I think it deals with using the encoder module for the parallel port, but you can just ignore that bit and just copy the bits where the signals are sent), but you'll probably want to allow a couple of inputs to define the step size as well.

Not a bad read here:
www.anderswallin.net/2006/11/jogging-emc2/#more-107

Quicker than editing a post

Some great ideas here
github.com/KurtJacobson/RF45-config

I use a modified version of the mpg.comp in my mill setup.

And cos I'm not the biggest fan of running multi core cables I use a Mesa 7i73 for my pendant.