New mpremote default soft-reset behaviour

[projectgus]

We've recently merged PR 17485 "mpremote: Make resume the default behaviour". The mpremote command line tool has new default behaviour in the nightly v1.30-preview builds, and this change will be part of the future MicroPython v1.30 release.

In MicroPython v1.29 and earlier, mpremote automatically soft resets the target board before running the requested commands. This means mpremote always starts from a minimal initial state, and any existing state (loaded code, set variables, etc) is lost each time it runs. In order to keep the existing state of the board there is a subcommand mpremote resume [command(s)] which skips the soft reset and "resumes" the existing Python programming session.

In MicroPython v1.30 and newer, the default behaviour is now resume - i.e. the board is not automatically soft reset, and when you run mpremote then it keeps the existing state of the board. There is a new subcommand mpremote soft-reset [command(s)] which you can use to soft reset the board before mpremote starts running the requested commands.

Most workflows will not need to change, but there are some subtle differences. For example, if you run import mycode on a board and then later use mpremote cp mycode.py : to copy a new version of the mycode module, MicroPython will still have the old mycode module imported until you trigger a soft-reset (either by running mpremote soft-reset cp mycode.py :, by typing Ctrl-D in the REPL, etc.)

It is possible to change back to the v1.29 default behaviour via a new setting in the mpremote config.py file. Adding the line auto_soft_reset = True will bring back the v1.29 default behaviour.

If you're writing a script that calls mpremote then suggest explicitly running mpremote soft-reset [...] or mpremote resume [...] each time, so correct behaviour doesn't depend on the local config.

For more details see this section of the mpremote documentation

Feel free to post a comment if this change breaks any workflows in a way which is difficult to accommodate.

[Josverl]

It would be helpful if there was a simple(r) way to install Mpremote preview from either the downloads pages, or from PyPI (preferred).

Installing from the GitHub repo will fail, at a pip install will attempt to recursive sync all submodules, and then time out.

So currently the only option is to clone, and then uv pip install micropython/tools/mpremote.

If we can make this simpler, we make it simpler to test all those tools that wrap Mpremote (yep, it's on my backlog as well)

[ubidefeo]

A week ago I sent a message to @dpgeorge with some special cases I find myself into that do require a soft_reset() (I use _thread and Timer), and our Lab for MicroPython editor does not currently soft_reset() on run/exec, so I was wondering if it was the case to force such behaviour, but Damien gave me some specific cases, such as the use of USBDevice which convinced me that this new behaviour might be the way to go.
I also pointed out that without soft_reset() imports are not updated and uPy has no facilities to force a re-import.
I guess in favour of supporting new features we have to adapt how we use mpremote (or how we mock it in case of our micropython.js module).

Thank you for adding soft-reset as a command.

I'm sold, new behaviour works for me 😄