Add endstop for trigger home position

[slimline33]

endstop

Hi techninja,

is it possible to add a endstop for cnc machine? or some code to trigger it? I think it's usefull also for robopaint, because I can add there also a #improvement

I already ask brian at schmalzhaus for trigger one or two i/o...

Greetings Christoph

[oskay]

Do you mean limit switches? The EBB does support digital inputs, but cncserver does not presently (so far as I know) have an API function that can query them.

[techninja]

Yup, CNCServer currently has no endstop trigger support. Stepper support works by internally assuming relative positions to extrapolate absolutes. Seeing as CNCServer has been built around only machines without these thus far, there's no real concept of it. It likely could be added around the existing API, but it couldn't be supported directly unless we had a specific machine in mind. Taking feedback from serial controller queries is extremely limited in current configurations and likely should be improved, but haven't had the need yet.

[oskay]

I would say that it would be plausible to add a specific command that would query the state of a digital input, using the EBB (UBW) "I" command.

[techninja]

A "query" API endpoint seems very reasonable, though a little slow for what would be needed here. A "seek to home" command basically needs to check this after every movement step. I'm going to take a wild guess and say that @embeddedman probably has some kind of firmware update that handles this use case a bit cleaner.

[oskay]

It is not currently implemented in the firmware, although we are discussing some changes for a major firmware update in the near future. This would be a good one to put on the list--

Move in direction (x,y) until input (z) changes state?

[EmbeddedMan]

Yes, doing it in the firmware as a a single command is the only good way to do it.

Would you really want to move both axis at once until a single input is tripped?

It seems like it would be easier to do one axis at a time. There also needs to be a timeout so that if the specified input doesn't change state in that time an error is returned.

We may also want to have a speed in steps/s that you can optionally specify for the command, so you could easily implement the "home fast, come off the switch, then home slowly until the switch just trips" thing that a lot of CNC machines do.

*Brian

On Tue, Aug 30, 2016 at 9:55 PM, Windell Oskay notifications@github.com wrote:

It is not currently implemented in the firmware, although we are discussing some changes for a major firmware update in the near future. This would be a good one to put on the list--

Move in direction (x,y) until input (z) changes state?

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/techninja/cncserver/issues/81#issuecomment-243644270, or mute the thread https://github.com/notifications/unsubscribe-auth/AAbeCLNtWOAo1ZsFBeHjXuuC05SsYZ31ks5qlO06gaJpZM4JwkVv .

[oskay]

If it can be specified in an arbitrary direction, then it allows for checking in XY or AB geometry, as well as upper and lower limits, without considering each case in particular.

As far as timeouts go... perhaps it would be best to implement this as an "SM" type command, but with an extra parameter indicates the digital input that will be monitored. That way, it would have a built-in timeout (and speed)-- if no limit is detected, it halts at the end of its given travel.

[EmbeddedMan]

Windell - yeah, I really like that idea a lot. A modified version of an SM command, so you get a move duration, a number of steps, and you could move both motors at the same time if you wanted to. In fact, what we could have is a new command called "EL" (Enable Limits). It would take four parameters. Axis1 limit switch port, Axis1 limit switch bit, Axis2 limit switch port, Axis2 limit switch bit. Once you send that command, the next SM command you send would check, in between each step, to see if the specified ports and pins changed state. If so, that axis would stop moving. After the SM command is done, you could send EL,X or something like that to turn that mode off (or maybe it would automatically turn off after the SM command is complete.) So the EL command puts the EBB into this 'use limits' state, for just one SM command.

That actually doesn't sound very hard to implement in the firmware actually. Just a few more instructions on each step.

*Brian

On Tue, Aug 30, 2016 at 10:13 PM, Windell Oskay notifications@github.com wrote:

If it can be specified in an arbitrary direction, then it allows for checking in XY or AB geometry, as well as upper and lower limits, without considering each case in particular.

As far as timeouts go... perhaps it would be best to implement this as an "SM" type command, but with an extra parameter indicates the digital input that will be monitored. That way, it would have a built-in timeout-- if no limit is detected, it halts at the end of its given travel.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/techninja/cncserver/issues/81#issuecomment-243646617, or mute the thread https://github.com/notifications/unsubscribe-auth/AAbeCLcBX80VVkbHpvXluH4jXZPFqHWWks5qlPFvgaJpZM4JwkVv .

[oskay]

Let's move the discussion about firmware implementations to the appropriate place: https://github.com/evil-mad/EggBot/issues/58

For the moment, back to the original question: perhaps we should add an API endpoint for digital input queries?

[slimline33]

nice to see there is a future plan :dancer: