ISO: Mesa to router interface board

I need hardware suggestions.  There seems to be a gap in my knowledge, and in my research.

I just got a new CNC router, and it came with a Grbl-based controller.  I always used LinuxCNC in the past on my DIY machine, and I can already tell that I'll probably be happier if I switch to LinuxCNC on the new one.

The most recent incarnation of the old machine was driven by a Raspberry Pi and a Mesa ethernet card.  The Mesa was connected almost directly to the limit and estop switches, and the step/dir lines went to a quad stepper driver board I got from Sparkfun a long long time ago.  The wiring was a horrible rat's nest of jumpers running between pin connectors glued upside down to a plank.  (I'm not exaggerating.) And I don't want to use the Sparkfun board again, for various reasons.

At some point I'm going to want to use the Mesa card with the new machine.  But what I'm picturing, that I don't have, is the "interface" board.  It needs to take 24V power, and have 3 or 4 of those little 16 bit stepper driver modules.  And it needs to have a bunch of screw terminal strips, set up to logically simplify the 6 or 7 pairs going to switches, the 3 or 4 connections to the motors, and all of the interconnect to the Mesa.  Basically what I want is an XYZ CNC router breakout board, with drivers.

But all I can find is complete controllers:  all of what I described, hardwired to an ATMega328, or ESP32.  Or, all of what I described, in the form of an Arduino hat.  Better, but still not very Mesa-friendly.

Can anyone point to the product I'm looking for?  Or tell me (nicely what I should be looking for instead?
 

As you're asking for an interface board I'm Gunna assume you have a 7c81 at hand.
The expensive route but most complete, reliable and expandle route would be a 7i76, not the ethernet version but a plain version that you connect via a ribbon cable. This will give you everything you need except the stepper drivers on board.
In all honesty as a preference I much prefer the "standard" type stepper drivers rather than the types used on the smaller desktop CNC toys and such.
Unfortunately as you've found out there's not a lot of breakout boards available that handle 24v signals, most will be a DIY thing.

No, what I have is a 7i96. Somehow I found wiring directly to it very awkward with my DIY mill. It's possible that that was because of the poorly designed stepper driver board I was using -- it's connections were hard to manage.

I did find an Arduino shield that does what I want and has screw terminals for all connections. And I think I can probably use it almost as is, simply by not plugging it on to an Arduino. Still thinking about that.

When you say "standard" stepper drivers, can you show me an example, including how they're typically mounted? It's true my head is probably stuck in the CNC toy world.

paul

AliExpress has carrier boards for the little step stick drivers, less than a dollar a pop. You would just need to make some cables with female DuPont connectors at one end and bootlace ferrules at the other, far better than bare wires. That's the setup I use for testing things rather than messing with the mill in the garage.

Those TB6600 modules sure seem like an awkward form factor, especially given you need 3 or 4 or 5 of 'em.

I realized I solved this problem, but never finished up this thread.  Parts of the solution might help someone else, so here goes.  It's a bit of a hack.  But a clean hack, as hacks go.  

To recap:  what I needed was the glue board(s) between the mill, the steppers, their drivers, and my Mesa card.  I'm not ready to switch to something like the TB6600 for the drivers, and even if I did, I'd still need mounting hardware, a new box, etc.  My shop is very small -- my mill basically fills the space it's in, up against a wall, tucked in between the workbench and some shelving.  No room for big new boxes.  Only small new boxes.

I searched for carrier boards which would hold multiple Polulu style driver modules, but came up empty.  Lots of carriers for just one, but none for four of them.  Seems odd, but I looked pretty hard.

What I ended up doing is leveraging the MKS router controller that came with the new mill.  It had the power distribution I needed, the sockets for the A4988 modules, headers that matched the stepper motor wiring, of course all of which I needed.  It also had the Atmel processor running Grbl, laser outputs, and some other stuff, which I didn't need.

And very conveniently, and unexpected, there is a header next to each Polulu socket which gives access to the step/dir/enable signals between the processor and each driver module.  I think these are probably there so that you could use the controller to drive external stepper drivers instead of the Polulus, but I realized that if I simply kept the processor in reset, it would be tri-stated, and I could instead use those headers as external inputs to the A4988 drivers.  In other words, I could use my existing controller as the "carrier" board I'd been looking for, with no modifications at all.  (The board has a header which makes the board reset signal available, normally connected e-stop.  I just jumpered it to ground.)

So that's what I did.  I have a (very small) box sitting next to the mill that contains the original mill controller (relocated -- it used to be mounted on the gantry), and the Mesa card.  The pre-made cables from the motors to the controller card were all long enough to reach the box, with no splicing.  (Yes, I know cardboard isn't optimum.  But getting it all working and enclosed came first.  I'll make a better box soon.)

 

I still needed a small interface board to make wiring the limit switches more tidy.  They're all too short to reach the Mesa directly.  At Adafruit, I found a small breakout board, intended for an RPi pico.  It's basically a bunch of screw terminals, .1" headers, and solderable grid, in a compact form factor, all for just $12.50:   www.adafruit.com/product/5907 .  That went into a small project box mounted on the gantry, and serves as the junction box where the limit switches, e-stop, and probe inputs all gather, and are wired in a bundle to the Mesa.  It gave me an organized place to join the +/- limit switches into single inputs, etc, but mostly it just a place to screw down wires in order to connect them together.

 

I know it wouldn't be everyone's design, but I'm happy with it for now, and it went together cleanly.