Homing / limits - the manual is misleading, possibly wrong

I glazed over the thread and the first issue I see is very common.
Stepconnf vrs editing.
Past simple machines, it's often necessary to edit the files by hand. Once you have done that a fair amount it's very familiar and direct.
Unfortunately stepconf and pncconf use different terms/hide some details to hopefully make some things easier, so it's not so easy to apply suggestions from editing files to stepconf's entry.

The real problem comes when power users/devs forget how difficult it is to get up to speed in linuxcnc. You have spent hours working with stepconf and reading docs etc and have a small window of knowledge that needs filled in and then they want you to throw that knowledge away and start a new path. They ask you to walk before you can crawl
It's human nature. They want you to speak in the INI language they speak rather then speak in your Stepconf language.

Stepconf is capable of setting up a machine with all home and limits on one pin.
you can set the latching direction, the homing direction. homing speed. there is no reason (in this case) to have to edit files. Now I haven't done this so it's possible there is a bug in there but in principle it's all there and was in fact considered in it's design.

If there is a specific question on homing or a opinion on the docs to help clearing the air then please ask the question.

Maybe stepconf needs to be more clear too.
For instance in pncconf (a similar styled program for mesa cards) it asks for homing speed and homing direction separately where as in stepconf you must know to add the negative sign to invert the direction.

Chris

Thanks for acknowledging my frustration Chris. You described it perfectly although to be fair a large part of it is my inability to understand !

I have gotten my original question about using a single input pin resolved and working. However, in the process it has now morphed into trying to understand exactly how these variables work. Maybe should have started a new thread ?

Not sure if you had a chance to look at the graphic I attached in the other thread but it attempts to show areas were I have questions and also areas where I think the documentation may be inaccurate or confusing.

Jay

There is a lot of text in that PDF...

If think maybe you got overwhelmed with info as as far as I can see the answers to all the questions in red are on the page.

Homing is difficult stuff. Lets see what clears the fog...

Making sure the axis direction is correct is the absolute first thing to do. Machine axis direction can be different from what the screen shows, as the screen shows tool movement where as the machine might be moving the table. All homing description is based on tool movement not machine movement. this is a very common problem.

Everything is referenced from the origin. but the origin can be anywhere (even outside where you can move believe it or not)

The homing switch sets where the origin is, but even it is referenced from the origin

The negative soft limits are the most you can move in the negative direction. (but they might not be negative in the absolute sense)

The positive soft limits are the same as above but in the positive direction.

Any of that help?

cmorley wrote:

There is a lot of text in that PDF...

If think maybe you got overwhelmed with info as as far as I can see the answers to all the questions in red are on the page.

Homing is difficult stuff. Lets see what clears the fog...

Thanks for your reply Chris.

cmorley wrote:

Making sure the axis direction is correct is the absolute first thing to do. Machine axis direction can be different from what the screen shows, as the screen shows tool movement where as the machine might be moving the table. All homing description is based on tool movement not machine movement. this is a very common problem.

I'm very familiar with this concept when operating the different kinds of CNC equipment but it sounds like it also applies to when you're setting things up in the software. Is that correct ?

cmorley wrote:

Everything is referenced from the origin. but the origin can be anywhere (even outside where you can move believe it or not)

... "Everything is referenced from the origin ..." This is very important information and probably the source of a lot of my confusion !!! I started to suspect this after I decomplied everything into that graphic I posted but missed this statement in the manuals even after reading it multiple times. I was calculating everything from the Homing trip points which seems more logical to me and I believe it's how I set up our Mach3 & Mach4 machines.

cmorley wrote:

[The homing switch sets where the origin is, but even it is referenced from the origin.
The negative soft limits are the most you can move in the negative direction. (but they might not be negative in the absolute sense)

That explains why the HOME_OFFSET in the example in the manual is a negative .070 and the MIN_LIMITS is zero !

cmorley wrote:

The positive soft limits are the same as above but in the positive direction.

Any of that help?

Tremendously !!! Thanks Chris.

I apologize to everyone for missing or not understanding the significance of the critical prerequisite information you shared in the manual. After rereading it again today I would suggest that it might benefit from being more clearly stated and given more emphasis due to its importance in setting things up correctly..

I'm very familiar with this concept when operating the different kinds of CNC equipment but it sounds like it also applies to when you're setting things up in the software. Is that correct ?

Yes

We had just revamped that document - as you can see in this thread - with lots of reality checks from users.
I can see if i can make it more clear.
thanks for the feedback

Chris

The funny thing about all this is that when I set my machine up in 2016 with the newly released V2.8, I thought the docs were perfectly clear and precise. I know there were some tweaks done. I hope we have not gone too much the other way now..

Hi rodw,

I saw in one of the threads that you had written the .ini AND the .hal files for your machine from scratch just using the manuals.

Based on that I suspect you're smarter than the average bear ...

I can tell you for myself that the way these types of technologies are typically documented (Linux, UNIX, programming languages) does not compute with the signals and pathways in my brain. Wish that wasn't the case.

I've never been able to put my finger on why that is but I suspect that I have difficulty keeping all the little pieces of info in my head long enough to fit them all together.

What works for people like me is to have ALL the information needed to perform a specific task together and in a linear sequence. If I have to read some of the info in one area and then jump to another section to learn or remember some other related detail I just end up lost and going in circles.

With everyone's help I finally understand how to set up homing and software limits in the .ini file and have updated the graphic I attached the other day in a way that works for me to help me remember how to do this. I'll send it later when I'm on my other computer where I did the work to see what you guys think.

Thanks again all.

Jay

Here's the updated graphic I put together for all the MS Windows brained people out there :blink



Thanks again everyone.

Having fun now !!!

Not quite right (and some of these I'm nit picking)

A,B,C,D and H are really points not distances. They are all referenced from the origin. Distance is the measurement between these points and the origin. (this is the nit picking part)

H (final home position) is referenced from the origin not from home_offset

You vertical text in blue says that B is home-offset = -.07 it's not it's the origin which is always 0
Home_offset is the distance between the home switch trip point and the origin. (between C and B )

Chris

jay.perez1 wrote:

Hi rodw,

I saw in one of the threads that you had written the .ini AND the .hal files for your machine from scratch just using the manuals.

Based on that I suspect you're smarter than the average bear ...
Jay

Only because I had to becasue the Mesa 7i76e was not supported by pncconf at the time so I copied someone else's config. Bear in mind back then getting a PREEMPT_RT kernel to use the fairly new Mesa ethernet cards was not trivial and the guys here talked me through how to patch and compile the Linux kernel on Linux Mint. From that point, I decided it would be a walk in the park to compile Linuxcnc from source. I won't say it was easy but I got it done! Then just after that inspired my my non-trivial journey, one of the guys did a tutorial on doing what I did with Mint, then just after that the Stretch ISO was released. So homing aside, its a lot easier today.

I did test 7i76e support by pncconf for cmorley at one stage before he released it...

BUt the key is that you knew something about CNC and I knew nothing so my journey to enlightenment was massive! BUt it can be done!