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Which reset pin to use - STM32F407VGT vs stm32f4_Discovery

Question asked by Vidar (Z) on Nov 30, 2013
Latest reply on Dec 15, 2013 by Vidar (Z)

In a new layout, my first with STM32F4 ARM, I have done as the refference manual for this family tells me to do when I where to connect the SWD/JTAG . I used PB4 for Reset (<b>nJTRST</b>) . However, I now see that the discovery board does not at all connect this pin to the built in stlink debugger. It uses the , well lets call it the main-reset pin, <b>nRST</b> on pad 14 for the mentioned chip.

Since I now have problems with stability when connecting my design to stlink I wonder if this could cause it? I have not yet tried to use NRST in stead but even if that solves my problems I feel that I need to know which pin is correct to be used?

Talking aboute problems, I am able to once in a time connect the target but I must have a breakpoint in startup entry, cause I will never run to main. Stepping through startup shows me that the debugger looses connection when startup is initializing memory (i.e. the second iteration of .CopyDataInit). And thats it. I then have big troubles reconnecting next time.

I find this dificult to understand cause I have developed the sw on the discovery board before porting the code that runs well on discovery. The only thing done when porting, since the layout on my board is pretty similar is that I have moved a few portpins. The startup is the same and the chip is the same. The problems occoures while the chip is running on internal clock..

The only thing.... among all others, that comes to my mind and which could cause this problem is the reset issue, maybe and powersupply. The powersupply seems fine though after checking.

Thanks in advance