heater stuck "on" during partial boot of marlin

hello
I am hoping someone can help me with this issue. I have built a larger printer (320mm x320mm x330mm) i am running it with a smart ramps on an arduino due.
the problem I am having is that the due hangs before totally loading marlin2. when this happens my hotend heater come on full and stays on until a reset. once mqrlin is fully loaded the hotend works fine, the same thing happens during fw upload, how do I stop the heater from coming on before marlin has taken control of the system? ive already cooked a couple of nozzles. I see this as a serious fire hazard. motors and shield run at 12v. hotend and bed are 24v through a separate mosfet board so there is minimal load on the mosfets on the ramps board as all they do is turn on the larger 24v mosfet board (bed and hotend). I surely hope someone can explain to me how to turn the heater off until everything is fully booted

Edited 1 time(s). Last edit at 02/21/2022 12:29PM by bushpig7.

Since this is happening when you upload new firmware thsi is happening at the bootloader stage. you need a custom bootloader that turns off the heaters first thing.

"you need a custom bootloader that turns off the heaters first thing."

thanks but from what I read, the arduino due's bootloader is burned in at the factory and cannot be easily changed. I don't read of anyone else having this issue so maybe i just have a bad board.perhaps you know how to program the bootloader on a due. everything i have found online says you cant change the bootloader. Theres no way i will go to sleep with this printer running, i cant trust it. im thinking that I may abandon the 32bit goodness of the due and get a re-arm coupled with a ramps 1.6.

Then your only option to to ensure that that default state of the pins when uploading firmware is accounted for in hardware.
Potentially as simple as adding a pull up resistor to the heater IO pins, presuming your mosfets are active low

Edited 1 time(s). Last edit at 02/21/2022 09:01PM by Dust.

I'm willing to try just about anything.....I've got other problems that gave appeared with this printer and it would be good to have this one dealt with....kindly elaborate. Is this something I solder in place or are you talking about a firmware configure I see the pull-up settings in marlin. ....is this what you are talking about......never had to use that stuff before so I'm completely drawing a blank.....I appreciate your reply and look forward to the next one

Well was hoping for some explanation on pull-up resistors but I guess you've run out of time. .....I suppose I can do research ony own