Recommended electrical connection for SWD/JTAG port

swinchen · ‎2013-04-12

Posted on April 12, 2013 at 20:09

Hi All,

I am building a custom board with a

STM32F415ZG

. I was wondering if there is any documentation recommending how to connect the debug header?

Is it safe to directly connect VDD to pins 1-2, GND to the numerous gnd pins, PA13 (SWDIO) to pin 7, PB14 (SWCLK) to pin 9, NRST to pin 15, PB3 (TRACESWO) to pin 13? I don't plan on using so JTAG so I would leave the others disconnected.

The only reason I ask is because I looked at a number of Olimex reference designs and noticed some pull-ups and series resistors. I in reading the datasheet that internal pull ups are enabled so I am not sure why Olimex is doing that. I figured I should ask before making a costly, game ending mistake!

Thanks,

Sam

#debug #programming #swd

Tesla DeLorean · ‎2013-04-12

Posted on April 12, 2013 at 20:46

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

You might want to consider the 10-pin Cortex header.

Pull/up down resistors are generally favoured, put the land pads on the PCB, you don't have to populate. They control your reset/power-cycling experience.

Series resistors tend to be placed to provide some protection (voltage disparities between host/target, current limiting), given the use cases for Olimex boards, I'd imagine they know a lot about customer returns, and damage issues. In a production test environment case I'd be less worried about them.

J-Link's inject 5V via pin 19 of the classic 20-pin ARM JTAG connector, use this to your advantage, or not.

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swinchen · ‎2013-04-12

Posted on April 12, 2013 at 21:20

Hmm,

They do some strange connections to the pins listed as ''No Connection'' in the ST-LinkV2 documentation:

https://www.olimex.com/Products/ARM/ST/STM32-E407/resources/STM32-E407_Rev_B1_sch.pdf

Perhaps the schematic is for their probe.

Can you (or anyone else) recommend a good probe? I was planning on the ST-Link V2 because I have experience with STM32F4-Discovery, and I know it works well in Linux without any strange proprietary drivers, but if there is a better option I would love to hear about it!

Thanks for the reply,

Sam