Linear scale correction: homing to index

andypugh wrote:

jtc wrote:

my suggestion (I don't know in it is possible, but I think so) is to use a MUX to be able to use 2 different following errors.

You can't do that directly, as following-error is not a pin. (it is read directly from the INI file).

It would be possible to do it by simply lying about the feedback position to the motion controller though

For example, if you net fb-loop axis.N.motor-position-fb <= axis.N.motor.position-cmd then no following error can ever happen.

To "lie" about position feedback you would take the difference between the two pins above, scale by a variable scale factor (using mux2 as suggested) then add the scaled f-error back on and pass that to the fb pin.

now looks it is on linuxcnc 2.7

It's there in the 2.6~pre too if I am not mistaken. But that doesn't mean that changing it also updates the value in the motion controller...

I ordered 1-micron resolution linear scales for the two Y joints and Z joint; these will arrive somewhere next week so soon I can do more testing. I did fool around a little with the HAL files, but until now I still cannot get rid of the following error when homing for the first time. Press F2 and ctrl-Home again, and no following error. If it nly happens once it is a situation I can live with for now until the machine construction is done. There is only so much I can so in an hour of spare time. But if homing three joints to index means I have to do the F2/ctrl-Home four times I think I quickly get tired of that.

DaBit wrote:

It's there in the 2.6~pre too if I am not mistaken. But that doesn't mean that changing it also updates the value in the motion controller...

I ordered 1-micron resolution linear scales for the two Y joints and Z joint; these will arrive somewhere next week so soon I can do more testing. I did fool around a little with the HAL files, but until now I still cannot get rid of the following error when homing for the first time. Press F2 and ctrl-Home again, and no following error. If it nly happens once it is a situation I can live with for now until the machine construction is done. There is only so much I can so in an hour of spare time. But if homing three joints to index means I have to do the F2/ctrl-Home four times I think I quickly get tired of that.

so if you update the value, linuxcnc continues using the value that is in the ini file?

I don't know. Easy to check though