AnsweredAssumed Answered

STM32F334 Programm doen't start withoput manual reset

Question asked by go.eric on Dec 12, 2016
Latest reply on Feb 3, 2017 by STM32Cube-T

Hi there,

I have a set of 3 pcb's that i am testing I have written a programm that used to work on a previous versionof the pcb, and there have been minor changes between the 2 Version.


The problem is that when i run the programm into debug mode ( ulink pro), the program runs fine on all three of them.


However, when i start the pcb in normal mode (i.a mcu is started without debugger, just when powering up the 3,3V on the input), only 1 of the 3 pcbs works, the other 2 not running (a led starts to blink when the program runs). Only a manual reset on the reset pin helps to start the program.


The reset pin is linked to an external pull up resistor of 15k and a capacitor of 100nf ( as advisedin the datasheet )

Rising time of the 3,3V is 2-3us , rising time on the Reset pin is in the few milliseconds domain.

We use all the recommanded capcitors on the VDD and VDDA pins , tied BOOT0 to GND, and use an external clock source of 24MHz (the instruction clock is then set to 74MHz, which is the max value admissible by the Device)

We use a Goldcap on the BAT input, that provides


Here are the things i tested so far:

- increasing and reducing the input cacpacitance on the reset pin to play with the rising time - FAIL

- reducing the pull up resistor - FAIL

- Check the soldering of the crystal oscillator, and the signals comming into OSC Input, the 24MHz looked good, so it was a FAIL again to solve hte problem.

- using the internal oscillator of 8 MHz - FAIL


Has anyone experienced such type of problems in the past , and iff yes , is there a solution to resolve it?

Thanks in advance for any help brought.