STM32F429ZIT6 doesn't start without debugging session

[Benjamin Brammer]

Hey Guys,

I have designed a custom board with the STM32F429ZIT6 which I programm with the STLink debugger together with TrueStudio. So far everything seems to work except that when I don't use a debugging session I have to manually make a reset on NRST pin or otherwise the processor will not start it's normal program execution. I have to do this every time power get's cycled.

I have one 4,7uF cap for overall buffering and then 10nF and 100nF at each Vdd and an extra ferrite bead for the Vdda pin but with 1µF and 10nF as a decooupling. I did not implemnt a 100nF cap from NRST to ground for short ESD burst but I doubt that this is the cause for the problem since after the manual reset everything works fine.

Do I maybe need a reliable power cycling with an external power supervisor chip doing the manual reset, or did I do something comepletely wrong?

My controller runs with 3,3V.

best regards

Benjamin

[Benjamin Brammer]

VCAP1/2 are present as 2,2µF . But I haven't programmed the brownout. And it seems as it is deactivated initially...I will try to get this fixed.

[Benjamin Brammer]

mhh....I programmed the option bytes via the ST-Link Utility to VBOR3 so level 3 which should be enough with 2,9V . sadly it still doesn't work...is it possible that the processor enters a fault handler for some reason that is not triggered in debugg mode?

[Benjamin Brammer · Accepted solution]

OK I programmed the optional bytes via the ST-LINK Utility. It didn't change the problem. But for a reason I don't know today in the lab it seems to work without a manual NRST reset. Strange to my believes but that's how it is now. Anyhow I think I will implement a robust POR circuit.

So for now it may seem as if the 100nF on NRST did the job. But I will watch this..