CircuitPython 8 safemode.py

safemode.py

# SPDX-FileCopyrightText: 2023 anecdata
#
# SPDX-License-Identifier: MIT

import json
import microcontroller
import supervisor

from ⚙️ import *

# safemode.py is the entry point for SAFE MODE (hard fault, etc.)
# store supervisor.runtime.safe_mode_reason since it won't be available during boot.py or code.py

# NVM Safe Mode - to cross-check against safemode reason
if microcontroller.nvm[NVM_INDEX_SAFEMODE] != SAFEMODESET:
    microcontroller.nvm[NVM_INDEX_SAFEMODE] = SAFEMODESET

# set up the safemode dict
safemode_dict = {}
safemode_dict["safemode_reason"] = str(supervisor.runtime.safe_mode_reason)
update_restart_dict_time(safemode_dict)  # add timestamp

# write dict as JSON
precode_file_write("/safemode.json", json.dumps(safemode_dict))  # use storage.remount()

if False:  # check for any safemode conditions where we shouldn't RESET
    pass
else:
    # RESET out of safe mode
    microcontroller.reset()  # or alarm.exit_and_deep_sleep()

Adafruit Learn Guide: "CircuitPython Safe Mode"
https://learn.adafruit.com/circuitpython-safe-mode

Adafruit Learn Guide: "CircuitPython Essentials: CircuitPython Storage" (writing to flash)
https://learn.adafruit.com/circuitpython-essentials/circuitpython-storage

nice!

Emoji's as imports. What is this chaos... I love it.

from 💣 import TotallySafeCodeNotA💥

from 📷import 🖼️ I could see some neat uses.

I wonder how do you test safemode.py. The documentation mentions supervisor.SafeModeReason.PROGRAMMATIC however there is not much about how to trigger it. I tried blowing the stack in code.py however that ends up with RuntimeError.

edit: I see now, the guide on https://learn.adafruit.com/circuitpython-safe-mode/safe-mode-reasons describes how to do it using microcontroller.on_next_reset(microcontroller.RunMode.SAFE_MODE)