docs: Add a "Reset and Boot Sequence" reference page.

projectgus · dpgeorge · commit 0e7c3901b897 · 2024-11-19T10:57:26.000+11:00
Previously individual ports documented these aspects to varying degrees,
but most of the information is common to all ports.

In particular, this adds a canonical explanation of `boot.py` and
`main.py`.

This work was funded through GitHub Sponsors.

Signed-off-by: Angus Gratton &lt;angus@redyak.com.au&gt;
diff --git a/docs/esp8266/general.rst b/docs/esp8266/general.rst
@@ -74,40 +74,7 @@ as possible after use.
 Boot process
 ------------
 
-On boot, MicroPython EPS8266 port executes ``_boot.py`` script from internal
-frozen modules. It mounts filesystem in FlashROM, or if it's not available,
-performs first-time setup of the module and creates the filesystem. This
-part of the boot process is considered fixed, and not available for customization
-for end users (even if you build from source, please refrain from changes to
-it; customization of early boot process is available only to advanced users
-and developers, who can diagnose themselves any issues arising from
-modifying the standard process).
-
-Once the filesystem is mounted, ``boot.py`` is executed from it. The standard
-version of this file is created during first-time module set up and has
-commands to start a WebREPL daemon (disabled by default, configurable
-with ``webrepl_setup`` module), etc. This
-file is customizable by end users (for example, you may want to set some
-parameters or add other services which should be run on
-a module start-up). But keep in mind that incorrect modifications to boot.py
-may still lead to boot loops or lock ups, requiring to reflash a module
-from scratch. (In particular, it's recommended that you use either
-``webrepl_setup`` module or manual editing to configure WebREPL, but not
-both).
-
-As a final step of boot procedure, ``main.py`` is executed from filesystem,
-if exists. This file is a hook to start up a user application each time
-on boot (instead of going to REPL). For small test applications, you may
-name them directly as ``main.py``, and upload to module, but instead it's
-recommended to keep your application(s) in separate files, and have just
-the following in ``main.py``::
-
-    import my_app
-    my_app.main()
-
-This will allow to keep the structure of your application clear, as well as
-allow to install multiple applications on a board, and switch among them.
-
+See :doc:`/reference/reset_boot`.
 
 Known Issues
 ------------
diff --git a/docs/esp8266/quickref.rst b/docs/esp8266/quickref.rst
@@ -163,10 +163,10 @@ sys.stdin.read() if it's needed to read characters from the UART(0)
 while it's also used for the REPL (or detach, read, then reattach).
 When detached the UART(0) can be used for other purposes.
 
-If there are no objects in any of the dupterm slots when the REPL is
-started (on hard or soft reset) then UART(0) is automatically attached.
-Without this, the only way to recover a board without a REPL would be to
-completely erase and reflash (which would install the default boot.py which
+If there are no objects in any of the dupterm slots when the REPL is started (on
+:doc:`hard or soft reset </reference/reset_boot>`) then UART(0) is automatically
+attached. Without this, the only way to recover a board without a REPL would be
+to completely erase and reflash (which would install the default boot.py which
 attaches the REPL).
 
 To detach the REPL from UART0, use::
diff --git a/docs/library/builtins.rst b/docs/library/builtins.rst
@@ -170,6 +170,10 @@ Exceptions
 
 .. exception:: KeyboardInterrupt
 
+   |see_cpython| `python:KeyboardInterrupt`.
+
+   See also in the context of :ref:`soft_bricking`.
+
 .. exception:: KeyError
 
 .. exception:: MemoryError
diff --git a/docs/library/machine.RTC.rst b/docs/library/machine.RTC.rst
@@ -83,7 +83,7 @@ Methods
    a `bytes` object.
 
    Data written to RTC user memory is persistent across restarts, including
-   `machine.soft_reset()` and `machine.deepsleep()`.
+   :ref:`soft_reset` and `machine.deepsleep()`.
 
    The maximum length of RTC user memory is 2048 bytes by default on esp32,
    and 492 bytes on esp8266.
diff --git a/docs/library/machine.USBDevice.rst b/docs/library/machine.USBDevice.rst
@@ -32,10 +32,10 @@ Managing a runtime USB interface can be tricky, especially if you are communicat
 with MicroPython over a built-in USB-CDC serial port that's part of the same USB
 device.
 
-- A MicroPython soft reset will always clear all runtime USB interfaces, which
-  results in the entire USB device disconnecting from the host. If MicroPython
-  is also providing a built-in USB-CDC serial port then this will re-appear
-  after the soft reset.
+- A MicroPython :ref:`soft reset <soft_reset>` will always clear all runtime USB
+  interfaces, which results in the entire USB device disconnecting from the
+  host. If MicroPython is also providing a built-in USB-CDC serial port then
+  this will re-appear after the soft reset.
 
   This means some functions (like ``mpremote run``) that target the USB-CDC
   serial port will immediately fail if a runtime USB interface is active,
@@ -44,9 +44,9 @@ device.
   no more runtime USB interface.
 
 - To configure a runtime USB device on every boot, it's recommended to place the
-  configuration code in the ``boot.py`` file on the :ref:`device VFS
+  configuration code in the :ref:`boot.py` file on the :ref:`device VFS
   <filesystem>`. On each reset this file is executed before the USB subsystem is
-  initialised (and before ``main.py``), so it allows the board to come up with the runtime
+  initialised (and before :ref:`main.py`), so it allows the board to come up with the runtime
   USB device immediately.
 
 - For development or debugging, it may be convenient to connect a hardware
diff --git a/docs/library/machine.rst b/docs/library/machine.rst
@@ -62,14 +62,13 @@ Reset related functions
 
 .. function:: reset()
 
-   Resets the device in a manner similar to pushing the external RESET
-   button.
+   :ref:`Hard resets <hard_reset>` the device in a manner similar to pushing the
+   external RESET button.
 
 .. function:: soft_reset()
 
-   Performs a soft reset of the interpreter, deleting all Python objects and
-   resetting the Python heap.  It tries to retain the method by which the user
-   is connected to the MicroPython REPL (eg serial, USB, Wifi).
+   Performs a :ref:`soft reset <soft_reset>` of the interpreter, deleting all
+   Python objects and resetting the Python heap.
 
 .. function:: reset_cause()
 
diff --git a/docs/library/pyb.rst b/docs/library/pyb.rst
@@ -147,10 +147,10 @@ Power related functions
    (internal oscillator) directly.  The higher frequencies use the HSE to
    drive the PLL (phase locked loop), and then use the output of the PLL.
 
-   Note that if you change the frequency while the USB is enabled then
-   the USB may become unreliable.  It is best to change the frequency
-   in boot.py, before the USB peripheral is started.  Also note that sysclk
-   frequencies below 36MHz do not allow the USB to function correctly.
+   Note that if you change the frequency while the USB is enabled then the USB
+   may become unreliable. It is best to change the frequency in :ref:`boot.py`,
+   before the USB peripheral is started. Also note that sysclk frequencies below
+   36MHz do not allow the USB to function correctly.
 
 .. function:: wfi()
 
@@ -205,8 +205,9 @@ Miscellaneous functions
 
 .. function:: main(filename)
 
-   Set the filename of the main script to run after boot.py is finished.  If
-   this function is not called then the default file main.py will be executed.
+   Set the filename of the main script to run after :ref:`boot.py` is finished.
+   If this function is not called then the default file :ref:`main.py` will be
+   executed.
 
    It only makes sense to call this function from within boot.py.
 
diff --git a/docs/pyboard/tutorial/reset.rst b/docs/pyboard/tutorial/reset.rst
@@ -10,6 +10,8 @@ execution of ``boot.py`` and ``main.py`` and gives default USB settings.
 If you have problems with the filesystem you can do a factory reset,
 which restores the filesystem to its original state.
 
+For more information, see :doc:`/reference/reset_boot`.
+
 Safe mode
 ---------
 
diff --git a/docs/reference/index.rst b/docs/reference/index.rst
@@ -21,6 +21,7 @@ implementation and the best practices to use them.
 
    glossary.rst
    repl.rst
+   reset_boot.rst
    mpremote.rst
    mpyfiles.rst
    isr_rules.rst
diff --git a/docs/reference/mpremote.rst b/docs/reference/mpremote.rst
@@ -547,9 +547,9 @@ device at ``/dev/ttyACM1``, printing each result.
 
   mpremote resume exec "print_state_info()" soft-reset
 
-Connect to the device without triggering a soft reset and execute the
-``print_state_info()`` function (e.g. to find out information about the current
-program state), then trigger a soft reset.
+Connect to the device without triggering a :ref:`soft reset <soft_reset>` and
+execute the ``print_state_info()`` function (e.g. to find out information about
+the current program state), then trigger a soft reset.
 
 .. code-block:: bash
 
diff --git a/docs/reference/repl.rst b/docs/reference/repl.rst
@@ -143,10 +143,12 @@ the auto-indent feature, and changes the prompt from ``>>>`` to ``===``. For exa
 Paste Mode allows blank lines to be pasted. The pasted text is compiled as if
 it were a file. Pressing Ctrl-D exits paste mode and initiates the compilation.
 
+.. _repl_soft_reset:
+
 Soft reset
 ----------
 
-A soft reset will reset the python interpreter, but tries not to reset the
+A :ref:`soft_reset` will reset the python interpreter, but tries not to reset the
 method by which you're connected to the MicroPython board (USB-serial, or Wifi).
 
 You can perform a soft reset from the REPL by pressing Ctrl-D, or from your python
@@ -182,6 +184,9 @@ variables no longer exist:
     ['__name__', 'pyb']
     >>>
 
+For more information about reset types and the startup process, see
+:doc:`/reference/reset_boot`.
+
 The special variable _ (underscore)
 -----------------------------------
 
@@ -196,6 +201,8 @@ So you can use the underscore to save the result in a variable. For example:
     15
     >>>
 
+.. _raw_repl:
+
 Raw mode and raw-paste mode
 ---------------------------
 
diff --git a/docs/reference/reset_boot.rst b/docs/reference/reset_boot.rst
diff --git a/docs/renesas-ra/tutorial/program_in_flash.rst b/docs/renesas-ra/tutorial/program_in_flash.rst
diff --git a/docs/renesas-ra/tutorial/reset.rst b/docs/renesas-ra/tutorial/reset.rst
diff --git a/docs/wipy/tutorial/reset.rst b/docs/wipy/tutorial/reset.rst
