Fischertechnik Interface with XY Plotter

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13 Nov 2013 04:23 #40773 by Flo1K
Hey Guys,

My name is Florian and I'm new to this kind if stuff.

I recently purched an old XY Plotter for small money and I wanted to use it with linuxcnc.

The problem is, the interface that cames with it isn't working as usual. It has an 8 bit shift register for I/O which is controlled by the parport. Now I question if it is possible to get a configuration that works with it.

Se this schematic for more details: www.ftcommunity.de/ftComputingFinis/interft.htm

So far,
Florian

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13 Nov 2013 19:37 #40784 by andypugh

The problem is, the interface that cames with it isn't working as usual. It has an 8 bit shift register for I/O which is controlled by the parport. Now I question if it is possible to get a configuration that works with it.


Possibly.

I can't really read German. Is the data sent digitally, or as step and direction signals with a clock and/or multiplexer?

Skunkworks recently managed to get an Emco lathe working with LinuxCNC which uses direct phase drive + a clock signal.
www.linuxcnc.org/index.php/english/forum...uxcnc-painless#36812

If it is a digital communication protocol, then Mesa, Pico and Pluto interfaces work this way, so it is entirely possible to do it, but a driver would need to be written. This might not be anything like as difficult as it sounds. Typically you use the "comp" hal function generator to create input pins for the XY commands, then assemble them into bytes in the required format, and send them to the port with an outb() command.
The following user(s) said Thank You: Flo1K

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14 Nov 2013 00:20 #40792 by Flo1K
Hi Andy,
thx for your reply.

As I understood, the interface outputs the state of the 8 bit output shift register directly by latching.

____Motor 1_ ____Motor 2_
| | | | | | | |
0 1 2 3 4 5 6 7 Bit

So the parport has to write a sequence of the signals for the phases with an 8 Bit latch cycle.

It isn't really a digital protocol rather raw serial data.

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14 Nov 2013 00:48 - 14 Nov 2013 00:48 #40794 by andypugh

So the parport has to write a sequence of the signals for the phases with an 8 Bit latch cycle.
It isn't really a digital protocol rather raw serial data.


This sounds quite a lot like the Emco interface that Skunkworks got working, have you read that thread?
Last edit: 14 Nov 2013 00:48 by andypugh.

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14 Nov 2013 01:10 #40796 by Flo1K
I'm not sure if I understood this right. Did he rip off the shift register and wired up the parport pins to the driver or not?

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14 Nov 2013 01:25 #40797 by andypugh

I'm not sure if I understood this right. Did he rip off the shift register and wired up the parport pins to the driver or not?


No, I think he persuaded LinuxCNC to drive the shift register.

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14 Nov 2013 01:36 #40798 by Flo1K
Umm .. he is pretending to us an octal latch but no shift in register. I think he can fed it directly with the stepper control data :unsure:

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14 Nov 2013 02:00 #40799 by PCW
Well a 8 bit latch is a 8 wide by 1 deep shift register... :)

You should be able to make a component (comp) that manipulates
the parallel port pins as required to drive your hardware.

linuxcnc.org/docs/html/hal/comp.html

Should get you started
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14 Nov 2013 03:29 #40802 by Flo1K
Thanks for your input guys.

Meanwhile I got some movement on the axis with an stupid windows software. I decided to build an interface with L297/L298 combo for more performance and option for a third axis.

Do you want to see pictures of the contruction as well?

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14 Nov 2013 07:03 #40805 by andypugh

Do you want to see pictures of the contruction as well?


Of course ;-)

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