demo_blink_led_asm bugfix

[vivi202]

This PR fix a bug that make demo_blink_led_asm not work as intended.

Example of the wrong behavior

This behavior is caused by the delay subroutine which sometimes doesn't work as it should.
The instruction add t1, t1, t0 can cause an overflow when mcycle is sufficiently large.
These overflows then leads to the delay_loop being skipped multiple times.

solution

I have solved this bug by using the MTIME module instead of mcycle, ensuring that every time the delay subroutine is called, the MTIME.TIME_LOW register is resetted back to zero, thereby avoiding overflows.

[stnolting]

Hey there!

I never thought about this overflow issue (and it seems like I did not run the problem long enough...) - so thanks for discovering this! 👍

I like your simple fix, but this requires that the MTIME machine timer is present in the system. Furthermore, MTIME is expected to show "wall clock" time so altering the MTIME counter during operation might not be a good thing (but that is not relevant for this minimal demo anyway).

However, what do you think about going back to the mcycle variant and clear that counter in the delay loop?

By the way, thumbs up for the illustrating video! 😉

[vivi202]

I agree with you, MTIME should not be altered, so i went back to the mcycle variant.

[stnolting]

Looks good to me! 👍
Were you able to test your new version? Is the overflow issue resolved?

[vivi202]

Yes i have tested it, and the issue is now resolved, i also finded a typo in the datasheet i can fix it here or i need to open another PR?

[stnolting]

Yes i have tested it, and the issue is now resolved

Great, thank you!

i also finded a typo in the datasheet i can fix it here or i need to open another PR?

If that is just a typo then just add it to this PR. 😉

[vivi202]

Great, thank you!

you'r welcome, thank you so much for making this awesome opensource project!

[stnolting]

Thank you very much 😉

Ready to merge?

[vivi202]

Ready to merge?

Yes.