LinuxCNC Feed Override: Configuring Joystick Control

Tom Garrett2 min read
Motion ControlOther ManufacturerTutorial / How-to
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Available HALUI Feed-Override Pins

The documented interface in the supplied configuration exposes the current feed override and incremental controls. It does not identify a pin that accepts an absolute floating-point command such as the joystick-derived range of -50 to 50.

HAL pin Evidence-supported function Use
halui.feed-override.value Current feed-override value Monitor the active override
halui.feed-override.scale Change applied to each command Set the increment or decrement size
halui.feed-override.counts Encoder counts used to change feed override Connect an incremental count source
halui.feed-override.increase Adds the configured scale Command an increase
halui.feed-override.decrease Subtracts the configured scale Command a decrease

Why the -50 to 50 Signal Does Not Connect Directly

The joystick produces -1 to 1. Applying a constant gain of 50 through mult2 produces -50 to 50, but the listed HALUI controls are incremental rather than an evidenced absolute-value input. Do not connect that signed output to halui.feed-override.value; the evidence describes that pin as the current value, not a command destination.

Use the joystick direction to select halui.feed-override.increase or halui.feed-override.decrease, and configure the amount per change with halui.feed-override.scale. If the input layer produces counts, connect those counts to halui.feed-override.counts. The available evidence does not define the conversion component, thresholds, update rate, or scale value, so determine those from the installed HAL components and required operator response.

Configure and Verify the Interface

  1. Confirm that the installed system exposes the halui.feed-override pins. The reported older EMC installation did not include HALUI and required an upgrade before this interface could be used.
  2. Choose an incremental command path: encoder-style input through halui.feed-override.counts, or directional commands through halui.feed-override.increase and halui.feed-override.decrease.
  3. Connect the selected command source and set halui.feed-override.scale to the required change per command.
  4. Move the joystick in each direction and monitor halui.feed-override.value. Verify that increase adds the scale and decrease subtracts it.
  5. Release or center the joystick and confirm that the override stops changing. If it continues, correct the direction thresholds or command-generation logic before operating the machine.

Joystick Jogging Is a Separate Function

Do not confuse feed override with axis jogging. The supplied working example routes joystick axes through sum2 and mult2 to halui.jog.0.analog, halui.jog.1.analog, and halui.jog.2.analog, while a throttle signal changes jog speed at runtime. Those pins command axis jog motion; they do not set feed override.

FAQ

Which LinuxCNC HAL pin sets feed override from a joystick?

The evidence identifies incremental controls: use halui.feed-override.increase and halui.feed-override.decrease, or send counts to halui.feed-override.counts. Set the change per command with halui.feed-override.scale.

Can I connect a -50 to 50 joystick signal to halui.feed-override.value?

No direct write path is supported by the supplied evidence. halui.feed-override.value reports the current value, while the evidenced command interface uses counts or increase and decrease inputs.

Why are halui.feed-override pins missing from EMC?

The reported installation was an older EMC version without HALUI. Confirm the installed version and upgrade to a release that exposes HALUI before configuring these pins.

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