[BUG] S-curve deceleration lost steps

[zhuxiufei]

Did you test the latest bugfix-2.1.x code?

Yes, and the problem still exists.

Bug Description

I tested the S-curve. In the deceleration stage, the last deceleration step could not reach the set end speed because of the accuracy of the floating point number conversion. (The cumulative value of deceleration time cannot reach the total deceleration time, but the number of deceleration pulses is reached)

Bug Timeline

No response

Expected behavior

No response

Actual behavior

No response

Steps to Reproduce

No response

Version of Marlin Firmware

marlin 2.1.x

Printer model

No response

Electronics

No response

LCD/Controller

No response

Other add-ons

No response

Bed Leveling

None

Your Slicer

None

Host Software

None

Don't forget to include

• A ZIP file containing your Configuration.h and Configuration_adv.h.

Additional information & file uploads

No response

[thisiskeithb]

Please download bugfix-2.1.x to test with the latest code and let us know if you're still having this issue.

Also, please attach your configs.

[ellensp]

And fill out "Steps to Reproduce" in detail.

[zhuxiufei]

run_logs.zip
The S-curve code was stripped, the test could run in linux or arm, and the deceleration was actually detected complete, but did not reach the final_rate problem

[zhuxiufei]

If I increase STEPPER_TIMER_RATE, things will improve. I suspect that calc_timer_interval will have a bias in the calculation and that this bias will accumulate,If the deviation between frequency and final_rate at the end of deceleration stage is large, it is easy to produce mechanical impact

[InsanityAutomation]

Can you see if the change in #26881 makes any impact to this, or if we are chasing a separate issue?

[github-actions]

Greetings from the Marlin AutoBot!
This issue has had no activity for the last 90 days.
Do you still see this issue with the latest bugfix-2.1.x code?
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