best way to use SWDIO and SWDCK

[montagnanigiovanni]

Posted on January 02, 2015 at 08:38

Hi everybody, i'm working on a custom board and experiencing a strange problem: if the two cables of SWDIO and SWDCK (they go from a stm32f4 discovery board to my board) are close Keil doesn't recognize the cortex device, if i keep them well separated everything works fine.

there is a way to have a better performance of this serial debugging feature?in my layout there is more than 1 cm between the two traces so i don't think that is a problem of crosstalk on the board.thank you so much for your help.have a good yearGio

[montagnanigiovanni]

Posted on February 04, 2015 at 10:04

any help or suggestion please? i still have to debug with a finger touching the the sdio connector..it's quite unconfortable :)

thankyou

[Tesla DeLorean]

Posted on February 04, 2015 at 14:04

How exactly do you have this all connected? Sounds like you don't have a good common ground between the boards/systems.

[montagnanigiovanni]

Posted on February 04, 2015 at 16:03hi clive.i use cn2 or cn3 from a stm32f4board i take swdio swdck, gnd and reset and connect them to my board's pins with wires.today i connected a 420pf capacitor to swdio and everything went good. but this afternoon i had to patch my board and again it started do act weird with the swd :(i do have gnd connected, tried different discovery and so on.now i'm waiting for a new pcb (this was a 2 layer diy board). hoping not to have the same problems!!