Merge pull request #3250 from videopixil/Minecraft_Compass

Minecraft GPS compass

Author: BlitzCityDIY

Minecraft_Compass/boot.py

@@ -0,0 +1,106 @@
+# SPDX-FileCopyrightText: 2026 Pedro Ruiz for Adafruit Industries
+#
+# SPDX-License-Identifier: MIT
+"""
+Minecraft Compass — boot.py
+
+Decides who can write to the CIRCUITPY filesystem this session, and
+handles any pending calibration write queued by code.py.
+
+Write access can only belong to ONE side at a time (the host computer or
+the running code), so this file picks based on whether the D5 side button
+is held during power-up:
+
+- D5 held at boot  -> COMPUTER edit mode. The filesystem stays in its
+  default state (host computer can write; code.py cannot). Use this to
+  edit code.py or hand-add waypoints to waypoints.json from a text editor
+  (paste coordinates straight from Google Maps).
+
+- D5 not held (normal boot) -> DEVICE mode. The filesystem is remounted
+  writable for code.py so it can save waypoints to waypoints.json in the
+  field. The host computer sees CIRCUITPY as read-only until the next
+  boot without the button held.
+
+Calibration still uses the NVM flow (unchanged): code.py sets NVM flags
+and soft-resets, and the pending action is applied here. That works in
+either mode because this file remounts writable when an action is queued.
+
+NVM layout (microcontroller.nvm):
+- Byte 0: Remount flag. 1 = a calibration action is pending this boot.
+- Byte 1: Pending action.
+            0 = no action
+            1 = write calibration data from NVM to settings.toml
+            2 = clear the MAG_ calibration keys to force recalibration
+- Bytes 2-29: 28 bytes of calibration data (seven 32-bit big-endian
+              floats): offset_x, offset_y, offset_z, scale_x, scale_y,
+              scale_z, heading_offset
+- Byte 30: theme index (managed by code.py, not used here)
+"""
+import struct
+import board
+import digitalio
+import storage
+import microcontroller
+
+ACTION_NONE = 0
+ACTION_WRITE_CALIBRATION = 1
+ACTION_CLEAR_CALIBRATION = 2
+
+# Read the D5 side button. It is wired active-low with an internal pull-up,
+# so a held button reads False. Released (normal boot) reads True.
+button = digitalio.DigitalInOut(board.D5)
+button.direction = digitalio.Direction.INPUT
+button.pull = digitalio.Pull.UP
+computer_edit_mode = not button.value  # held == edit from computer
+button.deinit()
+
+if computer_edit_mode:
+    # Leave the default mount (host computer keeps write access). code.py
+    # cannot save in this mode, which is fine while editing from a desktop.
+    print("boot.py: COMPUTER edit mode (D5 held) - host can write CIRCUITPY")
+else:
+    # Device mode: code.py gets write access so it can save waypoints.
+    storage.remount("/", readonly=False)
+    print("boot.py: DEVICE mode - code.py can write CIRCUITPY (host read-only)")
+
+# Apply any pending calibration action regardless of mode. The remount
+# above (device mode) already gave write access; in computer-edit mode a
+# calibration action is unlikely, but remount here too so it still works.
+if microcontroller.nvm[0] == 1:
+    if computer_edit_mode:
+        storage.remount("/", readonly=False)
+
+    action = microcontroller.nvm[1]
+    if action == ACTION_WRITE_CALIBRATION:
+        raw = bytes(microcontroller.nvm[2:30])
+        (
+            offset_x, offset_y, offset_z,
+            scale_x, scale_y, scale_z,
+            heading_offset,
+        ) = struct.unpack(">fffffff", raw)
+        with open("/settings.toml", "w", encoding="utf-8") as f:
+            f.write("# Magnetometer calibration — auto-generated by calibration.py\n")
+            f.write(f'MAG_OFFSET_X = "{offset_x:+0.4f}"\n')
+            f.write(f'MAG_OFFSET_Y = "{offset_y:+0.4f}"\n')
+            f.write(f'MAG_OFFSET_Z = "{offset_z:+0.4f}"\n')
+            f.write(f'MAG_SCALE_X = "{scale_x:0.4f}"\n')
+            f.write(f'MAG_SCALE_Y = "{scale_y:0.4f}"\n')
+            f.write(f'MAG_SCALE_Z = "{scale_z:0.4f}"\n')
+            f.write(f'MAG_HEADING_OFFSET = "{heading_offset:0.4f}"\n')
+        microcontroller.nvm[1] = ACTION_NONE
+
+    elif action == ACTION_CLEAR_CALIBRATION:
+        # Remove only the calibration keys this project owns, preserving any
+        # other entries a user may have added to settings.toml. With the MAG_
+        # lines gone, code.py sees no calibration and hands off to
+        # calibration.py on the next boot.
+        try:
+            with open("/settings.toml", "r", encoding="utf-8") as f:
+                kept = [line for line in f if not line.startswith("MAG_")]
+            with open("/settings.toml", "w", encoding="utf-8") as f:
+                f.write("".join(kept))
+        except OSError:
+            pass   # no file yet, or read-only: nothing to clear
+        microcontroller.nvm[1] = ACTION_NONE
+
+    microcontroller.nvm[0] = 0