A Distributed Control For Tool Changer in EMC

Hi group

I want to implement tool changer in a machining center.
I want to do this in a distributed control aproach. Since
i dont have any knowledge of coding for linux platform as well
as the tcl/tk language. I would like to just signal out serially the
tool changer information via single bit (it may be on lpt or STG)
The external 8051 compatible controller will handle the actual
tool changer task. the EMC will only signal this external controller
via single bit. Another input (it may be on lpt or STG) will be used
for EMC to get the status that the tool has successfully changed and
now it can go further to execute next command block.
i can very well handle the 8051 microcontroller part, so i think this
way i'd need to change less in the emc sources and most part i will
be able to manage outside of the emc box using some 8051 compatible
microcontroller, programmed in C.

The protocol i have roughly designed is as follows:
(i need your suggessions)

Protocol:
1. Machine axes go to home or tool changer location
2. EMC Sends 1 second low pulse
3. Toggle the output for specified number of tool number times
4. EMC waits for input low signal from external controller that tool
has been successfully changed
5. If external controller fails to load tool it activates the
Emergency stop signal.

Example to load tool # 1
1. Machine axes go to home or tool changer location
2. there will be output low for 1 second to tell external controller
to be ready for tool change.
3. then it will toggle the bit once to tell the external controller
that it should load tool #1.
4. EMC waits for input low signal from external controller that tool
has been successfully changed
5. If external controller fails to load tool it activates the
Emergency stop signal.

Example to load tool # 3
1. Machine axes go to home or tool changer location
2. there will be output low for 1 second to tell external controller
to be ready for tool change.
3. then it will toggle the bit thrice to tell the external controller
that it should load tool #3.
4. EMC waits for input low signal from external controller that tool
has been successfully changed
5. If external controller fails to load tool it activates the
Emergency stop signal.


for this whole process we'd need to spare only to port pins. one
for input and another for output.

As far as i have browsed the emc sources, i've figgured out that
i have two ways to accomplish this task.
one is to make changes in tkio.tcl source file to implment this
task. and another is to make changes in the bridgeporttool.cc
source file. I'd like to get some suggestion about what might
be the easiest way (i dont ask about the better or best method) to
accomplish this task?

In my opinion the editing tkio might be simpler. I've some queries
in my mind:

1. I'd like to learn the tcltk language used in the tkio source file
please tell me any web links to learn tcltk which can also teach
me how to access parallel ports.

2. how can i command from a tkio.tck source file to position any axis?
like sending any axis to go to home, or any particular position.
i want to know the syntax of code.

3. i also want to add spinde control functionality. i want to output
voltage proportional to the S code at any unused DAC of my
ServoToGo Model-II card. so i need to know how can i access the
DAC from tkio. i request ppl to tell me the fucntions those can
do this? I could see the parportSetBit fucntion in tkio.tcl
source file that can write to parallel port. but dont know how to
access STG-II cards ports (DAC,ADC and other parrallel ports)

4. Also i want to know how can i get hold of the spindle speed
and tool number variable of EMC? so that i can put a
corressponding voltage to some DAC or tool number information on
the port pin.


5. One thing that i dont understand is the NML. Please tell me how
does the c source files and the tcltk source files make use of nml?
does nml holds all off the variables used in emc? like
jog rate, spindle speed? tool number etc?

Thanks and best regards
Asim


PS: somebody post it to sourceforge i dont know how to post to sf
i am already member to sf but dont know the url to post from