Overwrite frozen main.py

[rolfbachmann]

Hello,

I've a RP2 project where I build my own firmware with some frozen python files (with manifest), say version.py and main.py. Works just fine, device boots up and run the main.py.

Now I need to do some further development, changed my main.py file and upload it to the device (by using mpremote), but the changes will not be executed. If I change the version number in version.py, which will be imported by main.py and upload the version.py this seems to work, I get another version number.

I found a comment from @robert-hh (https://github.com/orgs/micropython/discussions/14144#discussioncomment-8862144) where he said "there is a hiccup with main.py". I don't know if it's still valid.

My question:

• What's the best workflow to do further development on the frozen code?
• Does it make sense to move as much code as possible to other modules so I don't need to change the main.py?

I searched around for a while, but didn't find the right answer. Maybe I used the wrong search terms.

[andrewleech]

As long as you haven't also frozen boot.py, you should be able to use that to change the setup to load your new main

First thing to try is to change the order of sys.path. This list controls import location priority, where .frozen represents the frozen in code. If you insert / or /flash at the start of the list (can't remember which is appropriate for rp2) then it should get used before frozen.

With regard to the link, I know some ports support frozen main, but perhaps some others don't still? I'm not sure here, the main.c which handles the internal startup logic is separate for each port (has to handle custom peripherals etc) so there's some discrepancy here still.

[robert-hh]

It looks that I was wrong in my comment cited above. Like you noticed a frozen main.py will be executed if it exists. That was changed in 2019 (oops!).

[davefes]

Just a suggestion if CRTL-C is a problem. Maybe, start main.py off with:

# during development
if machine.reset_cause() == machine.SOFT_RESET:
    print('you got a SOFT_RESET, so do a machine.reset()')
    time.sleep(1)
    machine.reset()

and then some code in main.py if you want.

[rolfbachmann]

I've tried soft and hard reset with the same result: Reset always use the frozen main.py. I've to import main to run the "new" main. But it's ok for my dev workflow, if I really need to change the main.py.

[peterhinch]

One option is not to freeze main.py - put it in the filesystem. It's fine to mix frozen and non-frozen modules. Leave modules that are subject to change in the filesystem.

[bikeNomad]

I've done this in my frozen main.py to allow for /main.py to override:

import os

# allow for filesystem /main.py to override this one
root_files = os.listdir()
if 'main.py' in root_files:
    import main

else:
   # do normal stuff

And you can do the same thing in the frozen boot.py (after setting up sys.path):

root_files = os.listdir()
if 'boot.py' in root_files:
    import boot

Interestingly, what I get when I do both is this:

MPY: soft reboot
.frozen/boot: sys.path=['', '.frozen/app', '.frozen']
this is FS /boot.py
This is FS /main.py
start frozen main.py

That is, the .frozen/main runs after /main.py.