feat(docs): add sphinx doc builder

Krux lack of a techinical documentation. This commit add `sphinx` module
to generate a proper [readthedocs](https://readsthedocs.com/)
documentation for Krux firmware (and not a user documentation) and a
setup for install aditional deps, generation of rst files, build to html
files and serve.

Author: qlrd

.gitignore

@@ -86,3 +86,6 @@ krux-*/ktool*
 
 # IDE files
 .vscode
+
+# Readthedocs
+docs/_build/*

.readthedocs.yaml

@@ -0,0 +1,24 @@
+# Read the Docs configuration file
+# See https://docs.readthedocs.io/en/stable/config-file/v2.html for details
+
+# Required
+version: 2
+
+# Set the OS, Python version, and other tools you might need
+build:
+  os: ubuntu-24.04
+  tools:
+    python: "3.13"
+
+# Build documentation in the "docs/" directory with Sphinx
+sphinx:
+   configuration: docs/conf.py
+
+# Optionally, but recommended,
+# declare the Python requirements required to build your documentation
+# See https://docs.readthedocs.io/en/stable/guides/reproducible-builds.html
+python:
+  install:
+    - requirements: docs/requirements.txt
+
+

docs/Makefile

@@ -0,0 +1,20 @@
+# Minimal makefile for Sphinx documentation
+#
+
+# You can set these variables from the command line, and also
+# from the environment for the first two.
+SPHINXOPTS    ?=
+SPHINXBUILD   ?= sphinx-build
+SOURCEDIR     = source
+BUILDDIR      = build
+
+# Put it first so that "make" without argument is like "make help".
+help:
+	@$(SPHINXBUILD) -M help "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)
+
+.PHONY: help Makefile
+
+# Catch-all target: route all unknown targets to Sphinx using the new
+# "make mode" option.  $(O) is meant as a shortcut for $(SPHINXOPTS).
+%: Makefile
+	@$(SPHINXBUILD) -M $@ "$(SOURCEDIR)" "$(BUILDDIR)" $(SPHINXOPTS) $(O)

docs/conf.py

@@ -0,0 +1,331 @@
+# Configuration file for the Sphinx documentation builder.
+#
+# For the full list of built-in configuration values, see the documentation:
+# https://www.sphinx-doc.org/en/master/usage/configuration.html
+
+import os
+import sys
+import time as _time
+from unittest.mock import MagicMock
+
+"""
+`sphinx-*` tools used on `pyproject.toml` (specificaly, on `readthedocs` poe
+task) will execute the to bedocumented code before document it. But some of
+them are hardware specific (micropython selfcustody fork) and cannot be loaded.
+
+A way to "skip" them is to mock the libraries that we do not want to execute
+(hardware specific, embit, thirdparty, etc). After that we can configure 
+so `sphinx` could translate them to html.
+"""
+
+
+# -- Mock hacks----- ---------------------------------------------------------
+class MockDisplay:
+    """Mock display with proper return types."""
+
+    def height(self):
+        return 320
+
+    def width(self):
+        return 480
+
+    def draw_centered_text(self, *args, **kwargs):
+        pass
+
+    def clear(self):
+        pass
+
+    def fill_rectangle(self, *args, **kwargs):
+        pass
+
+    def draw_hcentered_text(self, *args, **kwargs):
+        pass
+
+    def draw_qr_code(self, *args, **kwargs):
+        pass
+
+    def to_landscape(self):
+        pass
+
+    def to_portrait(self):
+        pass
+
+    def __getattr__(self, name):
+        return MagicMock()
+
+
+class HashableMock:
+    """A simple hashable mock that can be used as dictionary keys."""
+
+    _counter = 0
+
+    def __init__(self, name="mock"):
+        HashableMock._counter += 1
+        self._name = name
+        self._id = HashableMock._counter
+
+    def __hash__(self):
+        return self._id
+
+    def __eq__(self, other):
+        if isinstance(other, HashableMock):
+            return self._id == other._id
+        return False
+
+    def __repr__(self):
+        return f"<HashableMock {self._name}>"
+
+    def __call__(self, *args, **kwargs):
+        return HashableMock(self._name)
+
+    def __getattr__(self, name):
+        return HashableMock(f"{self._name}.{name}")
+
+    def __int__(self):
+        return 0
+
+    def __bool__(self):
+        return False
+
+
+class MockModule(MagicMock):
+    """Mock module that returns HashableMock for attributes that might be used as dict keys."""
+
+    # Attributes known to be used as dict keys
+    HASHABLE_ATTRS = {
+        "MODE_AES",
+        "MODE_CTR",
+        "MODE_CBC",
+        "MODE_ECB",
+        "AES",
+        "CTR",
+        "CBC",
+        "ECB",
+    }
+
+    def __getattr__(self, name):
+        if name in self.HASHABLE_ATTRS or name.startswith("MODE_"):
+            return HashableMock(name)
+        return MagicMock()
+
+
+class MockWordlist:
+    """Mock for embit.wordlists.bip39.WORDLIST - returns list of strings."""
+
+    WORDLIST = ["abandon"] * 2048  # Dummy wordlist
+
+
+class MockTime:
+    """Mock time module with MicroPython-specific functions."""
+
+    def __getattr__(self, name):
+        if hasattr(_time, name):
+            return getattr(_time, name)
+        return MagicMock()
+
+    @staticmethod
+    def ticks_ms():
+        return 0
+
+    @staticmethod
+    def ticks_us():
+        return 0
+
+    @staticmethod
+    def ticks_diff(a, b):
+        return 0
+
+    @staticmethod
+    def ticks_add(a, b):
+        return 0
+
+    @staticmethod
+    def sleep_ms(ms):
+        pass
+
+    @staticmethod
+    def sleep_us(us):
+        pass
+
+
+# Create mock for board with required config structure
+class MockBoardConfig(dict):
+    """Mock board. config as a real dict."""
+
+    def __init__(self):
+        super().__init__(
+            {
+                "type": "rtd",
+                "lcd": {
+                    "height": 320,
+                    "width": 480,
+                    "invert": 0,
+                    "dir": 40,
+                    "lcd_type": 1,
+                },
+                "sdcard": {"sclk": 11, "mosi": 10, "miso": 6, "cs": 26},
+                "board_info": {
+                    "BOOT_KEY": 23,
+                    "CONNEXT_A": 7,
+                    "CONNEXT_B": 9,
+                    "LED_R": 14,
+                    "LED_G": 15,
+                    "LED_B": 17,
+                    "LED_W": 32,
+                    "BACK": 23,
+                    "ENTER": 16,
+                    "NEXT": 20,
+                    "WIFI_TX": 6,
+                    "WIFI_RX": 7,
+                    "WIFI_EN": 8,
+                    "I2S0_MCLK": 13,
+                    "I2S0_SCLK": 21,
+                    "I2S0_WS": 18,
+                    "I2S0_IN_D0": 35,
+                    "I2S0_OUT_D2": 34,
+                    "I2C_SDA": 27,
+                    "I2C_SCL": 24,
+                    "SPI_SCLK": 11,
+                    "SPI_MOSI": 10,
+                    "SPI_MISO": 6,
+                    "SPI_CS": 12,
+                },
+                "krux": {
+                    "pins": {
+                        "BUTTON_A": 16,
+                        "BUTTON_B": 20,
+                        "BUTTON_C": 23,
+                        "TOUCH_IRQ": 33,
+                        "LED_W": 32,
+                        "BACK": 23,
+                        "ENTER": 16,
+                        "NEXT": 20,
+                        "WIFI_TX": 6,
+                        "WIFI_RX": 7,
+                        "WIFI_EN": 8,
+                        "I2C_SDA": 27,
+                        "I2C_SCL": 24,
+                        "ENCODER": [10, 11],
+                    },
+                    "display": {"touch": True, "font": [12, 24], "font_wide": [24, 24]},
+                },
+            }
+        )
+
+
+class MockBoard:
+    """Mock board module."""
+
+    config = MockBoardConfig()
+
+    def __getattr__(self, name):
+        return MagicMock()
+
+
+# Create mock instances
+MOCK_TIME = MockTime()
+MOCK_UCRYPTOLIB = MockModule()
+MOCK_UCRYPTOLIB.aes = MockModule()
+
+# Mock for embit.wordlists.bip39
+MOCK_BIP39 = type("MockBip39", (), {"WORDLIST": ["abandon"] * 2048})()
+
+
+def setup_mocks():
+    """Setup all mocked modules."""
+
+    mock_display_module = MagicMock()
+    mock_display_module.display = MockDisplay()
+    mock_display_module.SPLASH = "Krux"
+    mock_display_module.FONT_HEIGHT = 24
+    mock_display_module.FONT_WIDTH = 12
+
+    mocks = {
+        # MicroPython built-ins
+        "machine": MagicMock(),
+        "board": MockBoard(),
+        "pmu": MagicMock(),
+        "time": MockTime(),
+        "lcd": MagicMock(),
+        "ujson": MagicMock(),
+        "urandom": MagicMock(),
+        "ucryptolib": MockModule(),
+        "uhashlib": MagicMock(),
+        "uhashlib_hw": MagicMock(),
+        "uctypes": MagicMock(),
+        "uos": MagicMock(),
+        "usys": MagicMock(),
+        "gc": MagicMock(),
+        # K210/Maix specific
+        "Maix": MagicMock(),
+        "fpioa_manager": MagicMock(),
+        "sensor": MagicMock(),
+        "image": MagicMock(),
+        "flash": MagicMock(),
+        # Crypto/QR
+        "secp256k1": MagicMock(),
+        "qrcode": MagicMock(),
+        # Embit (Bitcoin library)
+        "embit": MagicMock(),
+        "embit.wordlists": MagicMock(),
+        "embit.wordlists.bip39": MockWordlist(),
+        "embit.psbt": MagicMock(),
+        "embit.networks": MagicMock(),
+        "embit.descriptor": MagicMock(),
+        "embit.descriptor.descriptor": MagicMock(),
+        "embit.descriptor.arguments": MagicMock(),
+        # Scientific (if needed)
+        "numpy": MagicMock(),
+        "scipy": MagicMock(),
+        "scipy.linalg": MagicMock(),
+        "scipy.signal": MagicMock(),
+        # Krux specific
+        "krux.display": mock_display_module,
+    }
+
+    for mod_name, mock_obj in mocks.items():
+        sys.modules[mod_name] = mock_obj
+
+
+setup_mocks()
+
+# Add source path
+sys.path.insert(0, os.path.abspath("../"))
+sys.path.insert(0, os.path.abspath("../src/"))
+
+# -- Project information -----------------------------------------------------
+project = "Krux"
+copyright = "2022, MIT"
+author = "Selfcustody"
+release = "2022"
+
+# -- General configuration ---------------------------------------------------
+extensions = [
+    "sphinx.ext.autodoc",
+    "sphinx.ext.coverage",
+    "sphinx.ext.napoleon",
+    "sphinx.ext.viewcode",
+]
+napoleon_google_docstring = False
+napoleon_use_param = False
+napoleon_use_ivar = True
+templates_path = ["_templates"]
+exclude_patterns = ["snippets", "_static", "Thumbs.db", ".DS_Store"]
+
+# Suppress warnings
+suppress_warnings = ["autodoc", "autodoc.import_object"]
+
+# -- Options for HTML output -------------------------------------------------
+html_theme = "sphinx_rtd_theme"
+html_static_path = []
+
+
+def skip_mock_members(app, what, name, obj, skip, options):
+    """Skip mock objects that can't be documented."""
+    if "Mock" in str(type(obj)):
+        return True
+    return skip
+
+
+def setup(app):
+    app.connect("autodoc-skip-member", skip_mock_members)