Extending existing G38.2/G38.3/G38.4/G38.5 codes

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10 years 11 months ago - 10 years 11 months ago #65870 by DaBit

cmorley wrote: He means there is no status feedback in linuxcnc for these requests.


Exactly. I once read about a method using rtapi_xx calls to accomplish that, but one would want a simpler interface for that to define errors and corresponding reactions.

How do the guys retrofitting 'real' machines do this? These have sensors on just about everything.

andypugh wrote: I think you are making this too hard.
LinuxCNC supports tool offsets in all 9 axes.


Well, that is only valid if the sensitivity of the probe is a perfect circle (or half sphere).
Which it is not in case of the regular 6-point-contact Renishaw lookalikes like mine. Although I must admit that the inaccuracies caused by that seem to be far lower than the positioning accuracy.
But I wanted to see the deviations anyway, so I had to write code for that. Normally one needs to compensate for probe tip diameter also and do the probe_point=probe_point - tip_radius anyway. Writing a component that takes in the file with N calibrations points and do the math is not that much harder than considering 4 special X+/X-/Y+/Y- cases.





Probe tip diameter is 4mm, Radius turns out quite accurate.

The same with combining probes. I wrote a component that can combine N probes into one output:
Code:
PROBECOMBINE(9) HAL Component PROBECOMBINE(9) NAME probecombine - Combine multiple probes into one output SYNOPSIS loadrt probecombine [count=N|names=name1[,name2...]] [personal‐ ity=P,P,...] DESCRIPTION Component to combine multiple probe signals into a single out‐ put. Use the 'personality' value to determine the number of probe inputs; range is 1-32. The component functions as a selector switch which is actuated by an edge on one of the probe inputs. The probe that generates an edge is the one being sent to the output after debouncing. If more than one probe input changes in a cycle, the result is the logical OR of the changing probe inputs. Thus, if one is active the output goes to '1'. When a probe state goes from enabled to disabled, the internal probe output is pulled to '1'. This is a valid edge, and is reflected on the probe-out pin. This is done to notify LinuxCNC when communications fail or another error occurs; LinuxCNC will complain about the unexpected edge. To prevent the situation where a failed probe that pulls the output to '1' blocks further motion, an optional auto-deactivate timeout can be used. The probe output will be deactivated the timeout number of seconds after the last edge. USAGE EXAMPLE Say we have a toolsetter switch that is always attached and a touchprobe that is removable. Then, a valid setup could be: loadrt probecombine personality=2 addf probecombine.0 servo-thread net toolsetter_sw probecombine.0.probein-00 net touchprobe_sw probecombine.0.probein-01 net touchprobe_enabled probecombine.0.probe-ready-01 net pi probecombine.0.probe-out motion.probe-input setp probecombine.0.enable 1 FUNCTIONS probecombine.N (requires a floating-point thread) PINS probecombine.N.probein-MM bit in (MM=00..personality & 0x1f) Probe input probecombine.N.probe-activelevel-MM bit in (MM=00..personality & 0x1f) (default: 1) Probe active level. Usually '1' for high active probecombine.N.probe-ready-MM bit in (MM=00..personality & 0x1f) (default: 1) Probe ready signal. '1' when the probe is ready, '0' when not probecombine.N.enable bit in (default: 0) Enable module. Set to '1' after everything is configured to prevent false edges probecombine.N.probe-out bit out Combined probe output, connect to motion.probe-input PARAMETERS probecombine.N.debounce-cycles u32 rw (default: 3) Number of cycles used for debouncing probecombine.N.auto-deactivate float rw (default: 10.0) Auto-deactivate probe output this amount of seconds after the last edge. This is used to prevent a deacti‐ vated/removed probe from tying the probe output to high and generate errors downstream in LinuxCNC. Set to a neg‐ ative number to deactivate probecombine.N.dbg-probestate u32 r For debugging: combined probe state AUTHOR DaBit (dabitATicecoldcomputingDOTcom) LICENSE GPL LinuxCNC Documentation 2015-11-27 PROBECOMBINE(9)

Maybe it is overkill, maybe not. The worst that can happen is that it does not provide any benefits.
Last edit: 10 years 11 months ago by DaBit.

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10 years 11 months ago #65872 by andypugh

DaBit wrote: Exactly. I once read about a method using rtapi_xx calls to accomplish that, but one would want a simpler interface for that to define errors and corresponding reactions.


How about:
linuxcnc.org/docs/2.7/html/man/man9/message.9.html
The following user(s) said Thank You: DaBit

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10 years 11 months ago #65879 by DaBit
Nice, thanks!

BTW: results of probing the ring and producing calibration data. Graph shows the deviation of the measured diameter of 12.0027mm vs angle



This is fairly repeatable, also at different locations on the table. The probe seems far more accurate than the positioning since I cannot detect the lobing so all this is less useful than I initially thought it would be, but compensating still doesn't hurt.

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