A lot

H again,

I am running a fever, - and my mind is not focused. It's not that
I need to defend myself, but I don't like to mess up things -as I
have done.

Jon Elson: All you say is -as usual - correct!

There is many ways to do this, and I have been thinking of too many
at the same time. One problem is a general setup, versus my own
possible usage. So, let me just ask what you think of this:

You have the jog function, and there must be variables to it in the
shared memory space. What if you had switches that enabled the
handwheel signal - as jog commands. That should be clean and easy
enough. Would that satisfy your needs ?

Here is some setups:

Stg board - you use digital io for the switches, and a spare
encoder counter.

DRO board - same as above.

Par. Port - need some electronics, I guess, but you could also
use game adapter or com ports.

I don't know how the jog function is implemented, and you might wish
some software counters in shared memory. I think Fred would know
all that would be needed, so I am not going to do any guess work on
that part.

So would this be okay ? Is there other needs ?

I will forget about the stg and Dro boards, and focus on a machine
with steppers on the printer port. I don't know what pins are
available, but for 4 axis, I think you would need at least 6 inputs
for 4 axis. ( increment, decrement, X,Y,Z, C? )
You could clock these signals in: ( 1 input, 2 output ) using a
simple shift register.

You may consider the use of the modem control signals on a serial
port.
So the question should be - where to interface it ?

If I understood some of the things Fred said, - then I take it that
he would be willing to include options for a handwheel, but he
wanted to know how the users would like it, and how it should
function. ( Hit me hard if I am wrong, Fred )

So, I think it would be correct of us to specify how we think it
should work, and if it is useful. In the end, we will have to wire
this thing up, so I think we should look into the interface detail
as well.

This was what I had in mind, when I started to throw out ideas.
++++++++++++++++++++++++++++++++++++++++++++++

Okay, here is a little for those not familiar with shift registers:

It has two input lines, and one output line - connected to a - say
printer port :
It is CLK, STROBE, and DATA.

On the output of this little chip, you have 8 digital inputs.
The computer outputs a strobe pulse, and all the 8 inputs will be
latched. Then you send 8 clk pulses, and for each you receive one
of
the latched inputs on the DATA in line.

Here you have expanded 3 i/o lines to 8. - but you may connect
another chip on the end of the first one, and you read in 16
signals. You can just continue expanding the line.

Another chip, can do output - the same way.

This is how most "dongles" and other io stuff on a printer port does
it.

This is a TTL circuit you can pick up at the nearest Radio Shack for
less than a dollar.
++++++++++

I just wanted to point out that if there is a need for more inputs,
it can be done in a way all would be able to do it. But you would
need to define a common interface, or layout.
One could be to implement the keyboard arrow switches, or what ever
you would like.

I have not studied the EMC software, and I don't know what is
available. But the step motors are already taking up on port, and
there is some taken up on another. Mist on/off, coolant on/off -
all of these could use an chip like the above, and free up pins to
use for a handwheel.

I think I have said enough.

//ARNE