Controller board: ESP32 + 2x StepStick carrier (v0.4), FluidNC config

- KiCad project generated by pcb/tools (design, route, schematic, fab outputs).
- v0.4 fixes the v0.3 review findings: low-dropout 3.3 V regulator, OR'd 5 V
  supply, polyfuse, USB ESD protection, input clamps, ceramic decoupling at the
  drivers, A4988/DRV8825 jumper, ground stitching. DRC/ERC clean.
- v0.3 (as ordered) kept in pcb/archive/v0.3.
- FluidNC config.yaml for the board; rho hard limit on.

Co-Authored-By: Claude Opus 5.5 <noreply@anthropic.com>

pcb/fluidnc/config.yaml

@@ -0,0 +1,77 @@
+# FluidNC config for the SandTable Controller v0.3 (ESP32 + 2x DRV8825 at 1/32 step).
+# A starting point: not yet run on real hardware.
+#
+# Units
+#   X = theta (arm angle) in DEGREES
+#       200 steps x 32 microsteps x (80T hub / 20T motor pulley) = 25600 steps per arm turn = 71.111 per degree
+#   Y = rho (ball distance from the centre) in MM
+#       200 steps x 32 microsteps / (20T GT2 pulley = 40 mm per turn) = 160 steps per mm
+#
+# If an axis turns the wrong way, add :low to its direction_pin (for example gpio.19:low)
+# or flip one coil's plug.
+
+board: SandTable Controller v0.3
+name: Sand Table
+
+stepping:
+  engine: RMT
+  idle_ms: 255            # 255 = never switch the motors off, so the arm can't drift
+  pulse_us: 4             # DRV8825 needs at least 1.9 us
+  dir_delay_us: 2         # DRV8825 needs at least 0.65 us
+  disable_delay_us: 0
+
+axes:
+  shared_stepper_disable_pin: gpio.13   # high = drivers off (a pull-up keeps them off during boot)
+
+  x:   # theta, degrees
+    steps_per_mm: 71.111
+    max_rate_mm_per_min: 3600           # 10 arm turns per minute
+    acceleration_mm_per_sec2: 120
+    max_travel_mm: 360                  # only sets how far $HX searches; theta is unlimited
+    soft_limits: false
+    homing:
+      cycle: 0                          # not part of $H. With a hall sensor fitted, home theta by hand with $HX
+      positive_direction: true
+      mpos_mm: 0
+      feed_mm_per_min: 120
+      seek_mm_per_min: 720
+      settle_ms: 250
+      seek_scaler: 1.1
+      feed_scaler: 1.1
+    motor0:
+      limit_neg_pin: NO_PIN
+      limit_pos_pin: NO_PIN
+      limit_all_pin: gpio.35:low        # HALL connector (active low, pulled up on the board)
+      hard_limits: false
+      pulloff_mm: 5
+      stepstick:
+        step_pin: gpio.18
+        direction_pin: gpio.19
+        disable_pin: NO_PIN
+
+  y:   # rho, mm
+    steps_per_mm: 160
+    max_rate_mm_per_min: 1500
+    acceleration_mm_per_sec2: 100
+    max_travel_mm: 135
+    soft_limits: false
+    homing:
+      cycle: 1                          # $H homes rho
+      positive_direction: false         # the home switch is at the centre end of the arm
+      mpos_mm: 3                        # switch trips near rho 2 mm, then backs off 1 mm. Tune so Y0 is dead centre
+      feed_mm_per_min: 100
+      seek_mm_per_min: 600
+      settle_ms: 250
+      seek_scaler: 1.1
+      feed_scaler: 1.1
+    motor0:
+      limit_neg_pin: gpio.34:low        # HOME connector: switch COM to GND (pin 3), NO to signal (pin 2)
+      limit_pos_pin: NO_PIN
+      limit_all_pin: NO_PIN
+      hard_limits: true                 # patterns stay 1 mm past the switch (rho_min_mm = 3), so a press
+                                        # while drawing means lost steps: FluidNC stops at once by itself
+      pulloff_mm: 1
+      stepstick:
+        step_pin: gpio.27
+        direction_pin: gpio.14
+        disable_pin: NO_PIN