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tugbasiltu
tugbasiltu
Visitor II
March 4, 2014
Question

STM32F405RG SWDIO, SWCLK, SWO, NRST pin connections

  • March 4, 2014
  • 2 replies
  • 2495 views
Posted on March 04, 2014 at 12:59

Hi ,

I am about to draw the schematics of a card which has STM32F405RG on it. I want to program my card throug SWD port. I made the pin connections as I described below:

 NRST: pulled up to VDD with 100K

SWDIO: pulled up to VDD with 100K

SWCLK : pulled down to GND with 100K.

Are these conections are correct?

I have STM32F4 discovery kit when I look at the schematics of the discovery board I see that SWDIO is pulled to low, SWCLK is p?lled to high and NRST is pulled to high. However on the document

http://support.code-red-tech.com/CodeRedWiki/HardwareDebugConnections

 it is recommended to connect as I did.I could not decide which one is correct. I will be very glad if you can help me. Thank you very much. ..

tugba

#jtag
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2 replies

Tesla DeLorean
Tesla DeLorean
Guru
March 4, 2014
Posted on March 04, 2014 at 16:15

Can't say I'm seeing any pull up/down for the SW pins on the STM32F4-DISCO schematic.

I'd pull SWCLK/TCK low, though 100K is a tad on the weaker side.

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jpeacock2399
jpeacock2399
Associate III
March 5, 2014
Posted on March 05, 2014 at 01:07

As I recall there was an errata on the F1 series about JTAG pullups but for F4 series they aren't needed.  There are internal pullups on the pins when in JTAG mode.  I have several F4 boards with nothing on the JTAG lines but 10 ohm inline resistors and high frequency/low capacitance TVS diodes to clamp the lines to 3.3V.

Your references may be old, when only the F1 series was available.

  Jack Peacock

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