NUCLEO-F429ZI with own board / Reset Issues

[jRn]

Hello,

for a first design verification i am using a NUCLEO-F429ZI board mounted on an own PCB.

With my first board everything is fine and i have no issues. But with my second NUCLEO-F429ZI, the behaviour is strange.

I am using the same PCB and can change the NUCLEO-F429ZI.

On my PCB i am using the +5V (CN8_9) as supply for the NUCLEO-F429ZI. The jumper JP3 is on E5V, for programming during implementing. 

Now with the second board i have to press the RESET button or plug the USB ST-Link cable that the NUCLEO-F429ZI will start.

With the other one, there is no need to press the RESET button or plug in the USB ST-Link cable.

On the PCB i have a 10k pullup for NRST...

Thanks in advance!

BR,

Juergen

[Piranha]

> On the PCB i have a 10k pullup for NRST...

Then take it off and look at AN4488.

[jRn]

Hello Piranha,

thanks for the advice.

But it didn't work if i remove the 10k pullup...

I have already checked at AN4488 and still have no idea.

[Piranha]

> it didn't work if i remove the 10k pullup

Then fix it. Show/describe the complete schematic related to NRST signal. Check the NRST level.

Check the voltage on power supply lines with and probably take a look with an oscilloscope.

Debug the software...

[jRn]

What should i fix when i remove the pullup?

I have already checked the NRST signal with a osci. It is the same with the "working" Eval-Board.

I didn't think the power supply is the problem because after a "Reset" event it works fine..

How do i debug the software if the board wouldn't boot?

[Piranha]

If the hardware is fine, then most likely the MCU is starting, but the startup code fails at some point, which can be debugged.