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Using two concurrent ports
« on: April 10, 2020, 02:51:24 PM »
I apologize if this is dealt with in another thread (and am happy to be directed there,) my search did not ID one.

I'm using Mach3 on Windows 10 with a Langmuir Crossfire Plasma CNC (w/ the CrossFire Mach3 USB Motion Controller Plugin.)  The Crossfire controller does not easily support limit or home switches.  I would like to build a small independent arduino system with a couple of limit/home switches and use it concurrently in Mach3 while also controlling the Crossfire.

Any chance that Mach3 is capable of using two ports, one for the step/dir CNC controls and another for limit/home switches?

thanks in advance,
Re: Using two concurrent ports
« Reply #1 on: April 10, 2020, 10:19:12 PM »
Mach can have but one motion controller active at a time, in your case the CrossFire board.

You could have a second data input board but it will not be realtime.

Lets imagine the board you have has more capacity and had limits and home switches attached. If during
operation a limit switch activated the motion control board will cease movement IMMEDIATELY. It will also send
a signal to Mach so the screen is upadted.

If you have two boards, your regular CrossFire motion board and a second data input board then if a limit activated
on the second data board, it would send a signal to Mach, Mach would decide what to do and then send a signal (via the buffer)
to the motion board. So the delay between when the switch activated and when its gets enacted could be tens or even
hundreds of milliseconds, during which time your machine has crashed.

Limit and Home events need to be handled immediately, also said to be 'realtime', whereas relying on a second data
input board precludes ANY of the inputs to that board to be handled realtime.

You need another motion controller but with much greater IO so it can handle all the motors AND the limits/homes AND
the probe(s) AND the fans And the plasma machine controls, etc.

I would reccomend the Ethernet SmoothStepper, it has the equivalent of three IO ports for a total of 51 inputs and outputs.

'I enjoy sex at 73.....I live at 71 so its not too far to walk.'
Re: Using two concurrent ports
« Reply #2 on: April 11, 2020, 03:34:22 PM »
That's a fantastic response! It makes the implications of the options very clear. 
Thank you very much!

I've got a number of digital fab tools (Router CNC, laser engraver, 3D printers, etc.) and would love a generalized 'bolt-on' homing solution.  My current fantasy (after reading your post,) is to construct a microcontroller device that uses FETs or relays to 'buffer' the stepper motor inputs to the controller board.  Using momentary contact or optical sensors attached to the uC device, you could interrupt the power to the motors, bypassing the time lag incurred by round-tripping to the PC.  Given the variety of stepper wiring configs, you'd probably need at least 2 'buffers' per motor and on devices with dual motors for some Y axis configs, you'd probably need at least 6 buffers (8 to include a Z-axis,) with different plugs for different wirings.  But 8 relay boards with NC contacts are _cheap_!  Just setting one up for my plasma box would be a good start.

Thanks again!!
Re: Using two concurrent ports
« Reply #3 on: April 11, 2020, 04:00:57 PM »
you are trying to reinvent the wheel. Any good motion control board and appropriate home and/or limit switches
and it does all that you want, and because the time critical inputs, like limits and homes, are on-board the
response is near instant.

If you have multiple machines and of different types the I would recommend Mach4, it is designed to be flexible
to accommodate different machines and the Ethernet SmoothStepper has THE MOST COMPLETE suite of realtime
supports of ANY Mach4 step/direction controller.

You could waste huge amounts of time on a project such as you are talking about.....which could be achieved at a
fraction of the cost in money and time with an ESS.

'I enjoy sex at 73.....I live at 71 so its not too far to walk.'
Re: Using two concurrent ports
« Reply #4 on: April 12, 2020, 02:22:12 PM »
Your response is fair and undoubtedly accurate.  I've got a long history of building things that should never have seen the light of day.  ::)

Thinking through the details after posting (note the _after_,) I decided to dig deeper into the Crossfire controller.  Indeed, it supports four inputs and, with some undocumented wiring, works well providing Mach3 with limit/home inputs.

Thank you for taking the time to respond!