I'm making a stepper motor pulse generator for my own use but others
might find it useful.  To help make sure it is useful to others I'm
asking what specs it would need to have  to make in "interesting" to
you.

Here is what it does...   You send it via a serial link a point in 6
or 7 axis (x,y,z,a,b,c) and a time.  The pulse generator will step all
the motors such that they all get to the given point at the specified
time and the movement is along a straight line (in joint space).   The
units are "steps".  Also you can send it one point and then while the
motors are moving you send it the next point and it will go from one
to the next without stopping.  This way the serial link timing need
not be perfect.  As long as the next point is sent in time, the timing
is near perfect.

In my use case all of the move commands are sent at a given rate.  say
maybe 50 points per second.   The output pulses are "standard TTL"
five volts and maybe about 20 ma source/sink

Whatever sends the commands does all the inverse kinematics, real
world to joint space transform, acceleration control and so on.    All
this thing does is handle the real-time pulse generation so no hard
real time work must be done by the sender.    my target cost is "dirt
cheap".

Now for the survey questions:

1) what is the fastest pulse rate you would reasonably use.  The
DM542T driver I'm using for testing is spec'd to 200KHz but I can't
imagine anyone actually getting close to that.  What's a real number?

2) How much jitter in the pulse timing is acceptable?  Yes i know it
depends on the speed.

3) Are people using balanced signals on the step and direction pins.
I kind of doubt it but want to be sure.


I don't know if something like this could be used with MK, if so t
could offload all of the hard real-time requirements.    I need this
for a robot arm

-- 

Chris Albertson
Redondo Beach, California

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