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()

Nice. Yeah, my intention was to highlight the features of safemode.py, and carrying data forward through into boot.py and code.py. Hopefully folks modify and extend it to better suit their needs.

print() in safemode.py goes nowhere, hence the file write and nvm. print() in boot.py also goes nowhere except for getting appended to boot_out.txt, up to 512 bytes total (no serial console / REPL until [re]load / run time / code.py).

I mostly work with espressif and raspberrypi ports, and there are some differences that may be beneficial in either case. For example, espressif maintains the on-chip RTC time across soft resets, whereas raspberrypi does not. Also, there is a new PR to add sleep_memory on the raspberrypi port, and in that case sleep_memory survives not only deep sleep and reloads, but also soft resets (microcontroller.reset()).

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)