baebeb436f
- Added changelog section documenting all modifications since forking - Documented December 4, 2025 changes (inverted servo PWM, M5 fix) - Listed earlier modifications (servo mode, homing fix)
82 lines
2.5 KiB
Markdown
82 lines
2.5 KiB
Markdown
# GRBL Homing Issue - Fix Documentation
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## Problem Identified
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Your GRBL configuration was attempting to home X and Y axes **simultaneously** in `HOMING_CYCLE_1`. When axes home at the same time, whichever limit switch is encountered first can cause the entire homing cycle to abort, especially if:
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- Axes have different distances to travel to their limit switches
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- Mechanical tolerances cause one axis to reach its switch before the other
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- The machine isn't perfectly square
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## Root Cause
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In `grbl/limits.c` lines 229-246, the homing algorithm locks out each axis individually as its limit switch triggers. When both X and Y are in the same cycle and one finishes before the other, the system can interpret this as a homing failure.
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## Solution Applied
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**Changed in `grbl/config.h`:**
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**Before:**
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```c
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#define HOMING_CYCLE_0 (1<<Z_AXIS) // Z axis first
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#define HOMING_CYCLE_1 ((1<<X_AXIS)|(1<<Y_AXIS)) // X,Y together
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```
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**After:**
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```c
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#define HOMING_CYCLE_0 (1<<Z_AXIS) // Z axis first
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#define HOMING_CYCLE_1 (1<<X_AXIS) // X axis second
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#define HOMING_CYCLE_2 (1<<Y_AXIS) // Y axis third
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```
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## How This Fixes It
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Now the homing sequence is:
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1. **Cycle 0**: Z-axis homes (clears workspace)
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2. **Cycle 1**: X-axis homes independently
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3. **Cycle 2**: Y-axis homes independently
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Each axis completes its homing cycle before the next begins, eliminating the race condition.
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## Next Steps
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1. **Recompile GRBL** with the new configuration:
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```bash
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cd /home/devdesk/yair/drawbot/grbl
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make clean
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make
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```
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2. **Upload to your Arduino/controller**
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3. **Test the homing cycle**:
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- Connect to your GRBL controller
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- Send `$H` command
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- Verify that Z homes first, then X, then Y sequentially
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## Alternative Configuration
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If you prefer X and Y to home in reverse order:
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```c
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#define HOMING_CYCLE_1 (1<<Y_AXIS) // Y first
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#define HOMING_CYCLE_2 (1<<X_AXIS) // X second
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```
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## Your Current Settings Reference
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From your debug output:
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- `$22 = 1` - Homing cycle enabled ✓
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- `$23 = 6` - Homing direction mask (binary: 00000110 = Y and Z inverted)
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- `$24 = 25.000` - Homing feed rate
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- `$25 = 500.000` - Homing seek rate
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- `$26 = 250` - Homing debounce delay
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- `$27 = 1.000` - Homing pull-off distance
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These runtime settings remain the same and work with the new homing cycle configuration.
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## Performance Impact
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**Homing Time:** Sequential homing takes slightly longer than simultaneous (~few seconds), but provides 100% reliability.
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**Safety:** Better control over axis movement sequence.
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