CR10_STOCKDISPLAY with SKR E3 TURBO board gets a continuous SPEAKER output between POWER ON of printer and Marlin Boot Screen appearing on LCD

Bug Description

Hardware: CR10_STOCKDISPLAY off of an Ender3 PRO SKR E3 TURBO MCU board Connect EXP3 on back of CR10_STOCKDISPLAY connected to EXP1 on the SKR E3 TURBO board Turn the power on the SKR E3 TURBO and speaker produces a high pitch sound until the MARLIN boot screen appears. Once the Marlin boot screen appears the high pitch sound goes away.

The sound starts immediately after the firmware upload occurs.

I tried turning the cables around but then I lost the screen.

I tried disabling the #define SPEAKER in configuration.h but the sound still was produced.

I tried going into the pins_BTT_E3_TURBO.h file and disabling the BEEPER_PIN but it made it worse and it continuously produced a sound until the power was shut off on the printer.

I used this LCD adapter board from TH3D, https://www.th3dstudio.com/product/ezboard-creality-dual-lcd-adapter-board/
with the REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER but only enabled CR10_STOCKDISPLAY in configuration.h. The adapter board just combines the EXP1 and EXP2 into EXP3 port (I made no changes to the firmware) and the REPRAP_DISCOUNT_FULL_GRAPHIC_SMART_CONTROLLER came up and showed the Marlin display WITHOUT the noise!

Something is causing the speaker to start producing sound on the CR10_STOCKDISPLAY on the SKR E3 TURBO.

Since the LCD adapter board cover up other connectors I need on the SKR E3 TURBO, I was only left with one option. I cut the BEEPER line on the flat ribbon cable that goes to my CR10_STOCKDISPLAY. Once the BEEPER line was cut and the cable put back on the screen and on the SKR E3 TURBO board, I rebooted and the speaker no longer produced the sound.

I first ran into this with the Bugfix-2.0.x branch of Marlin, so I went back to the Release Branch 2.0.7.2 and the problem was there also.

Configuration Files

SKR E3 TUBO and CR10_STOCKDISPLAY.zip

Steps to Reproduce

Hardware: CR10_STOCKDISPLAY off of an Ender3 PRO SKR E3 TURBO MCU board Connect EXP3 on back of CR10_STOCKDISPLAY to EXP1 on the SKR E3 TURBO board Turn the power on the SKR E3 TURBO and speaker produces a high pitch sound until the MARLIN boot screen appears. Once the Marlin boot screen appears the high pitch sound goes away.

Expected behavior:

No high pitch sound to occur unless there is a issue with Marlin

Actual behavior:

High pitch sound occurs and their is not a problem with Marlin

Marlin says the following: https://github.com/MarlinFirmware/Marlin/issues/20646#issuecomment-753600246

This is not something that marlin can fix.
The issue is the boot loader needs to set the buzzer pin off.
You need a custom bootloader...

bigtreetech / BIGTREETECH-SKR-E3-Turbo