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CONFIG_VARIABLE_FEATURE.md

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Config Variable Access in OpenSBP

Overview

This feature allows you to reference configuration values from any config file in /opt/fabmo/config/ directly in your OpenSBP cut files using dot notation.

Syntax

%<config_name>.<property>.<nested_property>

Supported Config Objects

  • machine - Machine configuration (machine.json)
  • driver or g2 - G2 driver configuration (g2.json)
  • opensbp - OpenSBP runtime configuration (opensbp.json)
  • engine - Engine configuration (engine.json)
  • instance - Instance configuration (instance.json)

Examples

Accessing Machine Envelope Values

' Get the maximum X table limit (returns 36 for default config)
$xmax = %machine.envelope.xmax

' Get other envelope values
$ymax = %machine.envelope.ymax
$zmin = %machine.envelope.zmin

Accessing Machine Units

' Get current units setting
$units = %machine.units

Accessing OpenSBP Configuration

' Get move speeds
$xy_speed = %opensbp.movexy_speed
$z_speed = %opensbp.movez_speed

' Get jog speeds
$jog_speed = %opensbp.jogxy_speed

Accessing Driver/G2 Configuration

' Get G55 offsets
$x_offset = %driver.g55x
$y_offset = %driver.g55y

' Or use g2 alias
$x_offset = %g2.g55x

Using in Calculations

' Calculate center of table
$x_center = %machine.envelope.xmax / 2
$y_center = %machine.envelope.ymax / 2

' Move to center
MX, $x_center, $y_center

Backward Compatibility

The traditional numeric system variable format %(n) continues to work:

' Traditional format still works
$movexy = %(71)

Implementation Details

Modified Files

  1. runtime/opensbp/sbp_parser.pegjs - Grammar updated to support dot notation
  2. runtime/opensbp/sbp_parser.js - Parser regenerated from grammar
  3. runtime/opensbp/opensbp.js - Runtime evaluator updated to handle config paths

How It Works

  1. Parser recognizes %identifier.property.property... syntax
  2. Creates a configPath array: ["MACHINE", "ENVELOPE", "XMAX"]
  3. Runtime evaluator:
    • Maps first element to config object (e.g., "MACHINE" → config.machine)
    • Navigates through _cache using remaining path elements
    • Returns the value

Error Handling

  • Unknown config object: Error: Unknown config object: <name>
  • Invalid property path: Error: Property <path> not found in config
  • Variable not defined: Proper error message with line number

Testing

Test files created in /fabmo/runtime/opensbp/:

  • test_config_vars.sbp - Sample OpenSBP code
  • test_config_parser.js - Parser tests
  • test_runtime_config.js - Runtime evaluation tests

Run tests:

cd /fabmo/runtime/opensbp
node test_config_parser.js
node test_runtime_config.js

Notes

  • Config names are case-insensitive
  • Property names are case-insensitive
  • Nested properties are fully supported
  • Values are retrieved from the in-memory cache for performance