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Add fuses to disable system bootloader devices

Uwe Bonnes
Principal II

Hello,

reading

Hello,

Pristine STM32L431 PA6 turned to hard output

Pristine STM32L431 PA6 turned to hard outpu

I wonder why there are no fuses to turn selected bootloader devices of?

 

Cheers

2 REPLIES 2
tjaekel
Senior III

What do you mean?

Do you want to disable (via fuse burning, OTP memory) any bootloader?

Who would do this? (losing the option to reflash MCU even if debugger would not work anymore).

Please, STM team: do not allow to "burn out" a bootloader option (it is so helpful).

@tjaekel 

> Do you want to disable (via fuse burning, OTP memory) any bootloader?

Uwe said it quite clearly:

>> to turn selected bootloader devices off

This is to mitigate the risks bootloaders for certain peripherals involve by setting pins' pullups/pulldowns and, in some cases, setting them to hard output.

Clearly, Uwe wants to use the bootloader for some other peripheral, but wants to avoid the above risks for peripherals which he does not use.

Also,

> (losing the option to reflash MCU even if debugger would not work anymore)

no, by disabling bootloader entirely (for which there *is* option currently), you still can reflash MCU using SWD/JTAG.

JW

 

PS. We really should have a good and thorough (and by that, I mean not just throwing ideas around wildly, but paying very much attention to the detail) discussion on utility of the code in the system ROM. After all, it's silicon area and programming time we're paying for in every individual chip. Also, incidentally, this is *not* a hard fixed asset, as it's programmed during chip testing, so it *can* be changed (even if not expanded or moved) by ST even on existing chips - with all the caveats of introducing new bugs, backward compatibility, need for documentation, all the possible confusion etc., so it's highly unlikely ST is willing to participate to make it better. Way better. In fact, it could be made a talking point, with some (read: lots of) effort; but that's also exactly one of the few areas where community could genuinely contribute in a helpful way. OTOH, I am not sure the option bytes' functionality as such can be changed/amended.