Safe Boot

Safe Boot

If powering up normally or upon pressing the reset button, an SG Wireless module will boot into standard mode; the boot.py file will be executed first, followed by main.py. It is possible to alter the boot procedure of the module by tying certain pins high or low when the module boots.

Sometimes the code you have written will prevent you gaining access to the REPL or prevent you updating your code. Some example may be:

You disabled the WiFi/UART
Your code gets stuck before reaching the REPL
You set a socket as blocking but never receive any data

In order to fix this, you can safe boot your module. This will prevent boot.py and main.py from being executed and will drop you straight into the interactive REPL. After reset, if P12 pin is held high (i.e. connect it to the 3V3 output pin), the heartbeat LED will begin flashing orange slowly. If after 3 seconds the pin is still held high, the LED will start blinking faster. In this mode the module will do the same as previously explained but it will also select the previous OTA image to boot if you have updated the module via the OTA update procedure (updates performed via the firmware update tool do not count). This is useful if you flashed a OTA update that breaks the device. The F1 starter kit have a dedicated safeboot-button (SW201):

F1 Starter Kit

Pin P12 released during:

1st 3 secs window (slow flashing)	2nd 3 secs window (fast flashing)
Disable `boot.py` and `main.py`	Disable `boot.py` and `main.py` and use previous OTA firmware

The selection made during safe boot is not persistent, therefore after the next normal reset, the latest firmware will proceed to run again.

If problems occur within the filesystem or you wish to factory reset your module to remove your code, run following code in the REPL:

import os
os.fsformat('/flash')

Be aware, formatting the flash filesystem will delete all files inside the internal device storage (not the SD card) and they cannot be recovered.

Programatically enable safe boot

Next to the manual method to enter safe boot, it is also possible to enable safe booting in MicroPython using the following snippet, which is the same as pressing CTRL+F in CtrlR, and will not hold through a hard-reset:

import machine
import sgw
sgw.bootmgr(safeboot=True)
machine.reset()

Reset

Soft reset

SG Wireless devices support both soft and hard resets. A soft reset clears the state of the MicroPython virtual machine but leaves hardware peripherals unaffected. To do a soft reset, press Ctrl+D on the REPL or from within a script, run:

import sys
sys.exit()

Hard reset

A hard reset is the same as performing a power cycle to the device. In order to hard reset the device, press the reset switch or run:

import machine
machine.reset()