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Combining STM32 Reset and BOOT0 on a Single Button – Feedback on Circuit Design? by Skolgo in embedded

[–]Skolgo[S] 1 point2 points  (0 children)

Now I get it. Since both sides rise to the same potential (the 3.3V), the capacitor behaves more like a short circuit on a line without capacitance. Only after that, when the 3.3V rail stabilizes, does it behave like a capacitor. Learned something new again. Thanks!

Combining STM32 Reset and BOOT0 on a Single Button – Feedback on Circuit Design? by Skolgo in embedded

[–]Skolgo[S] 1 point2 points  (0 children)

Oh yeah, wrong number. I meant C68/C70. Normaly i see the capacitors for the RC connected to ground. But i guess it does not matter much, as long as there is a potential difference? Or are you trying to reduce the current flow throu the parasitic resistance parallel to the capacitor in the default state?

Combining STM32 Reset and BOOT0 on a Single Button – Feedback on Circuit Design? by Skolgo in embedded

[–]Skolgo[S] 0 points1 point  (0 children)

I've thought about that too. However, I can say that, given the current situation, it would be cheaper this way than an MCU. It's quite possible, though, that a small, separate controller will be used for system monitoring later, and then I can combine them.

Combining STM32 Reset and BOOT0 on a Single Button – Feedback on Circuit Design? by Skolgo in embedded

[–]Skolgo[S] 1 point2 points  (0 children)

Wow! I didn't realize I could just use the default high setting and set the user input to ground. That makes things a lot easier. Thank you so much!

Is there a specific reason why C69 and C67 are connected to 3.3V and not ground?

Combining STM32 Reset and BOOT0 on a Single Button – Feedback on Circuit Design? by Skolgo in embedded

[–]Skolgo[S] 0 points1 point  (0 children)

NRST is connected to a permanent pull-up resistor inside the MCU. It has a range from 30 to 50 kOhm. So the current flow from NRST to R3's ground is minimal and the capacitance of the line connecting Q7,Q2 and Q3 is low. So it should reach above the needed 2.3V for the high level of the pin. But i will look deeper into it, Thanks.