THERMAL_PROTECTION_GRACE_PERIOD is obsolete

[robbycandra]

SKR 1.3 Takes long time to boot up if the SD card enabled but SD card is not inserted.
This make the printer halted and show BED MAX TEMP error.

However if the SD Card is inserted or BLTouch ENABLED, BED MAX TEMP error never happened.

I measure on my printer, It need around 4 sec. So I make it 5 sec.

[robbycandra]

There is another issue about MAXTEMP at #14139

[thinkyhead]

Wow. Is this board actually unstable for 5 full seconds? Is something broken with its design?

[tpruvot]

the bltouch could slow down a lot the start
tip: tpruvot@4dd6248

[thinkyhead]

I see the thermal manager doesn't get initialized until after the SD card and EEPROM, which is all very sensible, since some of the temperature timer is bound to depend on loaded settings. However, I wonder if we could initialize that timer sooner so that ADC readings will start much earlier, perhaps even before the boot screen appears. Then the grace period can be timed from the start of ADC reading (instead of from where it is now handled, in manage_heater —called from idle— and applying a best-guess worst-case startup time).

[p3p]

I greatly reduced the Lowpass filtering on LPC based boards so it only takes 32 samples to converge, this shouldn't be an issue at all anymore, never-mind needing the grace period increased.

[thinkyhead]

@p3p — That's encouraging. The commit I just added doesn't change much, but saves 4 bytes of SRAM by not duplicating the grace_period variable, and is more explicit about where grace_period gets initialized.

[thinkyhead]

@robbycandra — Can you check to see that the lowpass filtering improvement has removed the need for a long grace period with the newest PlatformIO LPC core? If you can discover the minimum required grace period, that would be useful data for updating the default value.

[robbycandra]

@thinkyhead , great.. Now it can boot perfectly using Grace Period = 0. With SD Card Inserted or Not Inserted.

[robbycandra]

Do we still need Grace Period ?

I confirm that, With

  #define THERMAL_PROTECTION_GRACE_PERIOD 0

WIth SD Card inserted or Not, With BLTOUCH or Not.
Max Temp Bed Error Halt is not triggered.

I think it is save to remove THERMAL_PROTECTION_GRACE_PERIOD.

[thinkyhead]

I think it is [safe] to remove THERMAL_PROTECTION_GRACE_PERIOD.

I'll review the related issues to see if this was useful for any other platforms.