STM32L151C8 Keep freezing because of the NRST pin

[bakhti]

here is the pcb

tried adding a capacitor of 100nF to GND like it was suggested in the datasheet

still nothing the only work around i found is if i fiddle with a jumper between NRST and groud sometimes start the mcu or by touching the top of it with my finger as soon as i remove my finger it stop

[gregstm]

Is that just a two layer board? If so, the bottom layer should be mainly dedicated to ground plane. I don't see decoupling capacitors for the micro. Decoupling capacitors should be used as close as possible to the the micro with the minimum path from power pin to capacitor to ground plane - surface mount capacitors of course. The trouble with your NRST pin might be a symptom of a noisy board because of inadequate power supply decoupling of the micro. Careful design of power supply decoupling will make your board "quieter" for analog measurements and reduce the EMI it produces.

I'm sure ST have similar documents, but here is an older TI document I have found very useful over the years "PCB Design Guidelines for Reduced EMI" https://www.ti.com/lit/an/szza009/szza009.pdf

[gregstm]

Also, I assume you have a pull-down on Boot0 pin.

[Uwe Bonnes]

Without the recommended capacitor, short capacitive coupled pulses may win over the weak pull up on NRST and may reset the device.

[Tesla DeLorean]

It is a momentary switch, not a jumper.​

The pins should be high in normal operation.​

[bakhti]

no boot 0 is just floating a trid pulling it down no result

[bakhti]

yeah tested it with a scope and it showed 3.3v but the mcu keeps doing this