STM32F4RGT6 random initialization issue

[zexx86]

Posted on June 21, 2015 at 14:51

Hello again!

We have designed the board with this processor, it works perfectly.But in 1 : 100 times it seems as there is some weird condition and the processor wont initialize at all.If this situation happen, then I can re-power up the board as many times I want and it never boot up.Only when I wait few minutes it works again as without any issue.Then it works very well for next XXX power ups.I have found that when I discharge the capacitors then it works immediately again.So definitively there is some issue with the capacitors.I suspect that 47uF tantalum capacitor is not suited correctly.Please check my scheme.I have thought there is issue with BOOT0 pin, but it is not the case.Can you see something wrong in my design?It is not a problem with one particular board as the issue is happening with all assembled PCBs. So there is definitively design issue.Thank you very much for your great support!

[Tesla DeLorean]

Posted on June 21, 2015 at 15:24

Tying NRST to 3.3V is a very bad plan. The processor tries to drive this low, it's a bi-directional pin.

Consider also the initial state of BOOT1

[zexx86]

Posted on June 21, 2015 at 16:43

Oh, thank you very much. I didn't know that.

I have disconnected the NRST pin - we will see how it will behave. I have reviewed datasheet and I now understand why it should not be connected to VDD.Also it is recommended to use capacitor to avoid parasitic resets.