Add Albin's notes on GRBL firmware on SC machines

readme.md

@@ -13,4 +13,86 @@ A GRBL compatible controller for use as a drop-in replacement for the SC100 USB
   - Some juper block for IO-config
 
 Alvast een leuk plaatje:
-![PCB Render](images/render2_composit_web.png)
+![PCB Render](images/render2_composit_web.png)
+
+
+# Stepcraft 420 CNC settings with GRBLizer
+
+Notes kindly provided by [Albin Stigö](https://github.com/ast) on getting [GRBL v1.1](https://github.com/gnea/grbl/wiki) working with the
+[GRBLizer](https://github.com/eflukx/Stepcraft-GRBLizer) board.
+
+Tested on Stepcraft 420, but probably works with most other Stepcraft types.
+
+## Setup
+
+* Stepcraft 420 CNC
+* Stepcraft drivers with GRBLizer board
+* [GRBL v1.1](https://github.com/gnea/grbl/wiki)
+* [Universal-G-Code-Sender](https://github.com/winder/Universal-G-Code-Sender)
+
+Install GRBL in the usual way. However you need to make some changes in config.h and cpu_map.h.
+
+```c
+/* cpu_map.h */
+
+// The Stepcraft has all limits on one pin.
+#define X_LIMIT_BIT    1  // Uno Digital Pin 9
+#define Y_LIMIT_BIT    1  // Uno Digital Pin 9
+#define Z_LIMIT_BIT    1  // Uno Digital Pin 9
+```
+
+```c
+/* config.h */
+
+// Since all limit switches end up being shared on one pin, 
+// we can only home one direction at a time.
+#define HOMING_CYCLE_0 (1<<Z_AXIS)  // REQUIRED: First move Z to clear workspace.
+#define HOMING_CYCLE_1 (1<<Y_AXIS)  // OPTIONAL: Then move X,Y at the same time.
+#define HOMING_CYCLE_2 (1<<X_AXIS)  // OPTIONAL: Uncomment and add axes mask to enable
+
+// The stop output of the Stepcraft board is inverted to what GRBL expects.
+// However you simply can't swap the switch because the driver board will also
+// disable the motors so nothing will move.
+#define INVERT_CONTROL_PIN_MASK (1<<CONTROL_RESET_BIT) // Default disabled.
+```
+
+## GRBL settings
+
+I haven't done a lot of fine tuning but these seems to work well enough.
+
+```
+$0 = 50				(Step pulse time, microseconds)
+$1 = 100			(Step idle delay, milliseconds)
+$2 = 0				(Step pulse invert, mask)
+$3 = 0				(Step direction invert, mask)
+$4 = 1				(Invert step enable pin, boolean)
+$5 = 1				(Invert limit pins, boolean)
+$6 = 0				(Invert probe pin, boolean)
+$10 = 1				(Status report options, mask)
+$11 = 0.010			(Junction deviation, millimeters)
+$12 = 0.002			(Arc tolerance, millimeters)
+$13 = 0				(Report in inches, boolean)
+$20 = 0				(Soft limits enable, boolean)
+$21 = 0				(Hard limits enable, boolean)
+$22 = 1				(Homing cycle enable, boolean)
+$23 = 1				(Homing direction invert, mask)
+$24 = 120.000		(Homing locate feed rate, mm/min)
+$25 = 900.000		(Homing search seek rate, mm/min)
+$26 = 250			(Homing switch debounce delay, milliseconds)
+$27 = 1.000			(Homing switch pull-off distance, millimeters)
+$30 = 1000			(Maximum spindle speed, RPM)
+$31 = 0				(Minimum spindle speed, RPM)
+$32 = 0				(Laser-mode enable, boolean)
+$100 = 133.333		(X-axis travel resolution, step/mm)
+$101 = 133.333		(Y-axis travel resolution, step/mm)
+$102 = 133.333		(Z-axis travel resolution, step/mm)
+$110 = 800.000		(X-axis maximum rate, mm/min)
+$111 = 800.000		(Y-axis maximum rate, mm/min)
+$112 = 800.000		(Z-axis maximum rate, mm/min)
+$120 = 10.000		(X-axis acceleration, mm/sec^2)
+$121 = 10.000		(Y-axis acceleration, mm/sec^2)
+$122 = 10.000		(Z-axis acceleration, mm/sec^2)
+$130 = 300.000		(X-axis maximum travel, millimeters)
+$131 = 420.000		(Y-axis maximum travel, millimeters)
+$132 = 140.000		(Z-axis maximum travel, millimeters)
+```