Index homing Heidenhain ls 403/exe602

stanki-used.com.ua/image/PASSPORT/CNC/LS-403_LS-403C.pdf

I have the "C" version of the scale.

From what i understand it should be possible to calculate the absolute position on the scale by traversing past two reference marks. See picture 4 on page 9.

OK, That's entertaining...

It should be possible to home by using a component that
measures the distance between index's and only arms
the actual index logic by simulating home switch detection
when the correct inter-index distance is measured.

I believe there's no way to avoid using a home sensor. Because if the machine is left at the last index on the encoder line, when searching for the next index marker, it might hit the limit switch. But when you have a home sensor, it's much easier—you only need to check the first, closest index marker.

It seems the machine originally homed this way, but yes, you need to
guarantee the you are 2 index marks away from the end stop before
starting homing.

As far as I know nobody has done this yet, but the change that allowed one to use a custom homing component was put in to support this type of scale.

How's your C coding?

www.linuxcnc.org/docs/devel/html/man/man9/homecomp.9.html

github.com/LinuxCNC/linuxcnc/blob/07cee8...nts/homecomp.comp#L4

However, I don't know if that is strictly necessary. I think that it _might_ be possible to craft a custom HAL component that outputs an encoder position and handles index_enable. This would take the encoder counts as input, and also manipulate the index_enable pin of the encoder counter. (I think it would be necessary to use the position-latching facility of the software or Mesa encoder. I _think_ you can set index-enable, which will zero the counts when the first index is seen, then re-enable index-enable and look at the counts-latched pin when index-enable resets on the second index. But I have not tried this.)

The component would then reset the index-enable that the homing system sees, and pass the correct position into the system. (Note that the "correct" position might be the inverse of the actual position, in some way. The position-after-index-enable is used by the system to calculate how far the current position is from the home position.

component inputs:
index-enable - to / from motion system
encoder position - from encoder counter
position-latched - from encoder counter

outputs:
index-enable - to manipulate the encoder counter
encoder-position - an offset version of the encoder position input

I do have a Heidenhain scale, but i have never done anything with it, and don't know if its a type with encoded index marks.

Unfortunately I do not have any coding experience...

like i mentioned in previous post a "C" at the end "LS 403 C", indicates you have a distance coded version of the scale. Do you also have an interpolator like the exe 602?

I doubt i'll manage to HAL such a custom component myself, but I have my mill moving and would of course be willing to do some testing if someone has some time over to give it a try!

/Hampus