Fix autoreload on SAMD21

[tannewt]

The issue was that a time.sleep() would set the RTC wake up
further into the future even if we wanted to tick every ms. Ticking
every ms is used to time the autoreload delay and without it,
autoreload doesn't work.

Fixes #3528

[tannewt]

@todbot, this should fix the autoreload issue.

[gamblor21]

Built and tested on a Feather M0 Basic that I had tested the issue on previously. These changes fix the problem.

[jepler]

I didn't see anything to be concerned abut in the re-organization of _port_interrupt_after_ticks, and at a high level the explanation of the problem makes sense. No testing performed.

[todbot]

I'm curious: what's the device-based testing regime like? Is that documented somewhere? I'd like to get into testing stuff like this and would like to leverage any existing work.

And thanks for such a quick turnaround on this!

[tannewt]

I'm curious: what's the device-based testing regime like? Is that documented somewhere? I'd like to get into testing stuff like this and would like to leverage any existing work.

I think you are assuming we're more rigorous than we are. I just replicated the problem and then fixed it. I didn't test on other devices. I rely on folks trying their own main builds and the latest from S3 as a way to find other issues.

You can test PR changes by either pulling the PR down and building locally or waiting for the CI to complete. Once the CI is complete, you can access the built versions by:

1. Open the build results page by clicking any of the "Details" links. Example: https://github.com/adafruit/circuitpython/pull/3532/checks?check_run_id=1233432700
2. Click "Artifacts" in the top right and select the board of interest. It will download a zip of all the different language builds for a board. This button only appears after the entire build is complete.

And thanks for such a quick turnaround on this!

No problem! It's core to the CircuitPython experience so it's good to get fixed.

[todbot]

oh wow I didn't realize you had CI produce artifacts for every board for every PR! Go github actions I guess eh? This is much easier than the process I just did. (the standard PR pull, build via cmdline, and fish out firmware.uf2)

[tannewt]

Yup! It's nice but a little slow. :-)