STM32L4 Bootloader Wishlist Item

Discussion created by riggs.rob on Feb 19, 2017

I have designed a number of boards recently using STM32L4 chips (432, 443, 476) and have hit one issue repeatedly.


I have used a pin for GPIO which is also used by a bootloader peripheral which, in turn, causes the board to misbehave.


This is because the bootloader has a wealth of options -- peripherals it can boot from.  I am certainly not complaining about that.  STM has done a great job here.  However, some of the active bootloader peripherals will enable pull-downs that interfere with my needs.  In my case it has caused a needed power domain to shut down and another time held a device needed during bootloading in reset.


So... my suggestion is quite simply is this: provide options bytes which allow the developer to control which peripherals the bootloader is allowed to use.



At the same time, I should note that this is not all bad news.  I have also used this to my advantage.  By connecting an LED to a pin that is pulled down by a peripheral activated by the bootloader, I am able to provide a visual indication that the bootloader is active.