For a upcoming project I have a need for a microcontroller that can "self update" - load new code and logic at runtime. So far my thoughts where that I would use two ESP devices, one as the "version controller/updater" and the other one for logic. Recently I came upon the Raspberry pico and saw that it was using micropython that basically uploads python files to pico "storage". I am unfamiliar with this system, but would I be right to presume that it could just "create" these files on it's own and execute as it seems they are interpreted by some micropython loader? Google doesn't really have any results on this.
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1 Answer
MicroPython source code that you place in your board's flash memory is interpreted at runtime, and MicroPython has access to the filesystem on the flash memory, so the answer is yes: you can create or modify Python code in files on the device's filesystem and then execute them.
Here is a quick example I have tested in the Wokwi online emulator; I haven't tested it on a real board but have no reason to believe it would behave differently:
import time
import os
time.sleep(0.1) # Wait for USB to become ready
os.mkdir('foo')
with open('foo/foo.py', 'w') as f:
f.write('print("foo!")')
from foo import foo
When you run this it prints foo! to the MicroPython console.
You can run MicroPython on ESP8266 (depending on memory) and ESP32 boards as well as on the Pico, so you might not even need to switch hardware if you are already using the ESP. The MicroPython documentation describes the differences between boards.
Allowing your code to download and run external code creates a potential security vulnerability of course, so you should consider whether this is an issue in your project.
5 Comments
Lee-xp
Agreed. Tested your code on a physical Pico w and it worked first time.
somerandomusername
Hmm nice. This could be a potential direction for me to take.It seems it is not possible to "self" reflash in arduino runtime. Only other option I can think of is to have two controllers.
David C. Rankin
If you are looking for something with the same format (size) that gives you all the tools you have on a full Linux OS, why not a Pi zero 2 W? With 512M RAM and built in MicroSD (now readily available in 1/2 terrabyte cards) they are incredibly capable.
somerandomusername
@DavidC.Rankin This is a viable option. My only issue would be the boot up time. Google says it is 8s, but that is with GUI. Can’t find how fast that would be in headless. Anything above 3s would be a dealbreaker
David C. Rankin
3 sec is about right. I have 2 running headless on the coffee table in front of me I"m ssh'ed into working on ADC code. The pi-imager installs Debian Bullseye. Works great. gcc 10.2.1, Python 3.9.2 (and PostgreSQL and MariaDB, and nginx and PHP and ....) It's a full desktop in a package the size of a gum-stick. They run forever. The only thing they lack is built-in ADC (I've got an ADS1115 and MCP3008 on a breadboard). Pico does ADC natively -- which will spoil you. Another option is MilkV-Duo. (pico format, but with 64M or 256M RAM and native MicroSD - runs Busybox)
openocdto tranfer new code to the pico - I don't no if similar exists for python.