Author Topic: parrallel pin out and comms with driver board  (Read 1881 times)

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Offline boots_n_braces

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parrallel pin out and comms with driver board
« on: July 04, 2011, 12:18:46 PM »
Hi all, Ive been tasked with a current project that requires some dc servo control and mach seems like a good option for control how ever i have a few questions, this wont be a 'standard' machining use and as such everythings having to be designed from scratch. The majority of the work is done but im wondering about mach's protocols  (this may be silly as ive not had anything to do with cnc software before) i.e when mach outputs a number of pulses coresponding to encoder counts does it pause for a set time while the action is carried out or does the driver board give mach a sequence completed signal so it can send the next steps? and is there a pinout anywere for the parrallel port connection and machs uses for each pin? Ive tried some of the pdfs but cant seem to find anything?

Thanks
Harry

Online Tweakie.CNC

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Re: parrallel pin out and comms with driver board
« Reply #1 on: July 04, 2011, 12:38:16 PM »
Harry,

On the main Mach screen open Config / Ports and Pins. There are tabs for Input Signals and Output Signals - these will show you the available pin numbers and their allocations which you can set as required.

Tweakie.
Success consists of going from failure to failure without loss of enthusiasm.  Winston Churchill.

Offline boots_n_braces

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Re: parrallel pin out and comms with driver board
« Reply #2 on: July 04, 2011, 02:08:48 PM »
Brilliant thats going to make life a lot easier! any idea on how mach synchs the steps i.e if in psuedo code i ask it to go 20 steps cwise x axis then 10 acwise y axis how does mach calculate when the 20 x axis steps are completed is it open loop time based or does it have a count signal from encoder or a completed signal from driver board?

really appreciate the help

Offline djc

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Re: parrallel pin out and comms with driver board
« Reply #3 on: July 04, 2011, 04:22:37 PM »
...any idea on how mach synchs the steps i.e if in psuedo code i ask it to go 20 steps cwise x axis then 10 acwise y axis how does mach calculate when the 20 x axis steps are completed is it open loop time based or does it have a count signal from encoder or a completed signal from driver board?

It's open loop. Mach sends out the steps and assumes the machine does what it's told. Partial closing of the loop can be done in the servo drives themselves, but the best you can do is send a servo fault error back into Mach and cause it to stop.

Have a Google around for open vs closed loop. The debates can be tedious, but if you accept that Mach is open loop, you make sure you build the mechanics big and stout enough so this is never a problem.

If you want closed loop, you might have to look at EMC.