Welcome to LinuxCNC.org

A few observations:

1. Why are you not using the drive enable outputs of the 7I77? That is their intended purpose. They have the advantage that they are "floating" switches so can be used with active high and active low enables. They have the additional advantage that they can use a separate supply so you can use them with enable inputs that have a different voltage requirement than the field I/O (which is normally 12 or 24VDC)

2. HM2 encoder "Counter mode" which is an up/down count mode
as opposed to the normal reversable quadrature mode is not suitable
for MPGs so this should be set false

andypugh wrote:
Thanks a lot for the references. I wasn't aware that xenable wasn't a LinuxCNC function. That said, xenable is netted to axis.0.amp-enable-out later in the HAL file. Maybe I should take a look at that signal to see what it's doing.


andypugh wrote:
I have no jog speed selector switch or buttons so that's probably the problem. I'd just like to be able to set a fixed jog speed for the joysticks I have and use the MPG in velocity mode.

PCW wrote:I suspect that the simple answer is "Because Chris has never seen one", but also because that is specific to the 7i77 and pncconf is generic.

It would be very nice if pncconf could interrogate the hardware rather than using predefined config files, but I have not figured out how to do that.

PCW wrote:
1. I am not using them because it was negligibly easier to use an x-enable function with the existing circuitry. If it's going to make things more complicated, I can easily switch to those drive enable pins. I'll give that a shot. Did you have any thoughts on the positive feedback phenomenon?

2. I'm sorry but how do you know it is in counter mode and how would I change that?

Thank you.

If the existing enables work I would not bother at this point but it does add some design contraints that may be a problem later on (you need to have active high enables on your drives that will work with the common field voltage for all isolated I/O)

To fix a positive feedback problem (and assuming your encoders are counting in the proper directions, if the encoder count backwares, reversing the sign of the encoder scale (or swapping encoder leads) will fix the problem) you need to reverse the output. I _think_ this is done by changing the sign on the appropriate maxoutput variable (But Andy should be consulted on this as its not in the hm2 manual yet)

as far as counter mode goes, your example hal file had set counter mode true here:
setp hm2_5i25.0.encoder.05.counter-mode true
(which you do not want)

PCW wrote:The existing enables don't work. The relay that enables the axis drives do work with a field I/O level signal but the 7i77 isn't turning them on when it should.

PCW wrote:
It appears that you're right about reversing the output. I physically reversed the connections on the amplfier input signal and I don't seem to be getting the positive feedback anymore. Scale may be the one that needs to get negated.

Thank you for the counter mode assistance.