LIMIT_AXIS(9)

💖 NAME 💖

limit_axis — dynamic range based axis limits ✨ (yes bestie, your axis gets limits, but make them move with the vibe)

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🌸 SYNOPSIS 🌸

loadrt limit_axis [count=N|names=name1[,name2...]]
       [personality=P1,P2,...]

🦋 DESCRIPTION 🦋

Okay so this is limit_axis.c — it clamps an axis to certain limits at varying inputs. Like, the limits aren't fixed, they change depending on what some feedback pin says. Think of it as a bouncer who changes the rules depending on how tall you are. No cap.

Example time, because the example ate: say you've got a spindle with C rotation, and you're trying to avoid hitting a gantry when the height is above Z-10:

• Use the Z axis as feedback
• Use 2 ranges: (0,-10) and (-10, -40)
• When Z is above 10, C rotation is limited to range 0
• When Z is below 10, C rotation is limited to range 1

Slay. That's the whole concept.

Usage:

loadrt limit_axis count=3 personality=2,3,2

or

loadrt limit_axis names=limit_x,limit_y,limit_z personality=2,3,2

The personality argument defines how many ranges are supported by each instance. It's literally the range count per instance, periodt.

Heads up bestie: no spaces can be used in the names= and personality= parameters. Not even one. Zero. 😤

⚠️ Caveats ⚠️

• Searches ranges from 0 to 9 and will take the first range that matches
• Ranges are inclusive: min_range <= feedback <= max_range
• Max can not be less than minimum for any group
• Sticky indicates, to not check other ranges if the feedback is still in the current range
• Enable allows for a range to be turned on/off — for cases such as avoiding a tool changer, but allowing sometimes

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🔥 FUNCTIONS 🔥

• limit-axis.N — requires a floating-point thread 💅

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👑 PINS 👑

• limit-axis.N.error-no-range (bit out) — error pin indicating that no range matches the fb 😭
• limit-axis.N.min-output (float out) — minimum limit output
• limit-axis.N.max-output (float out) — maximum limit output
• limit-axis.N.fb (float in) — feedback pin; the value of this pin determines which range is active 🎯
• limit-axis.N.current-range (u32 out) — indicates which range is currently active
• limit-axis.N.min-limit-MM (float in, MM=00..personality) — the array of minimum limits to select from
• limit-axis.N.max-limit-MM (float in, MM=00..personality) — the array of max limits (the OG page spells it "macimum", iconic typo, we keep it in spirit 💀)
• limit-axis.N.min-range-MM (float in, MM=00..personality) — defines the range of values with which the fb is compared to set the range
• limit-axis.N.max-range-MM (float in, MM=00..personality) — defines the range of values with which the fb is compared to set the range
• limit-axis.N.enable-MM (bit in, MM=00..personality) — used to enable and disable a specific range 🎚️
• limit-axis.N.sticky-MM (bit in, MM=00..personality) — used to make specific range 'sticky' or not 🍯
• limit-axis.N.error-range-MM (bit out, MM=00..personality, default: 1) — error bit indicating that the fb pin falls outside all ranges
• limit-axis.N.error-limit-MM (bit out, MM=00..personality, default: 1) — error bit indicating that the max limit is not larger than the min limit

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🌈 AUTHOR 🌈

Chad Woitas 👏 (we stan)

💜 LICENSE 💜

GPL — free as in freedom, bestie

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Anyway that's the whole page from the LinuxCNC Documentation, dated 2026-03-17 — the LIMIT_AXIS(9) section of the HAL Component manual, section 9 and all. Go limit some axes responsibly fr fr 🫶✨🎀