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DStan.2
DStan.2
Associate
May 3, 2020
Question

What are the max values of resistors /capacitors that can be connected to PA13 and PA14 so the SWD debug is still working? I cannot find the info in any documentation.

  • May 3, 2020
  • 5 replies
  • 1358 views

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5 replies

TDK
TDK
May 3, 2020

I think the best approach is to minimize capacitance and see what works. The clock is configurable and can be slowed down, so unless you load a ridiculous cap on the line, you’ll be able to find a speed at which it works.

nucleo boards have a 22 ohm inline resistor.

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DStan.2
DStan.2Author
Associate
May 3, 2020

What about resistors, will an 1k resistor from pin to ground affect the debugging SWD functionality? Is there any documentation on what can be attached to the pins and still work?

Tesla DeLorean
Tesla DeLorean
Guru
May 3, 2020

Use some common sense, the signalling is on the order of 4 MHz, don't stick an RC circuit on the pins that will impeed usages.

No particular need for strong pullups either, just increases current.

​

What is your secondary use case for the pins?

What part are we talking about?​

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TDK
TDK
May 3, 2020

> Is there any documentation on what can be attached to the pins and still work?

I don't think you're going to find documentation for non-standard uses of these pins. There is general GPIO pin frequency characteristics listed in the datasheet. You can use that to guide your decisions.

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