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STM32F042 problem with SWD

Question asked by hermansson.mikae.001 on Nov 6, 2016
Latest reply on Nov 7, 2016 by hermansson.mikae.001
Hi I have designed my first PCB ever so sorry if ask stupid quetions.

The thing is my board has MCU STM32F042 and is based on nucleo reference design but for some reason I can not connect my stlink to using a nucleo stlink module in "stand alone mode".

It seems STM does not respond. When connected nucleo Stlink its led stays red. Notice I only connect SWDCLK and SWDIO and GND pins and this setting works an a board bought from ebay without problem and also on STM I have used at my work.

My schematic can be found at:

https://github.com/mike7b4/solary2_pcb/blob/master/pdf/solary2.pdf

I have only soldered the capasitors, STM and 3v LDO(notice shematic says 3.3v it it is 3v LDO) the rest of the components is not connected. no external crystal or its caps are connected since this should not be needed when test. 

So LDO put out 3v as expected stable after around 2uS and no ripple on upstart. However I noticed SWCLK gives 3v even if stlink is not connected. Reading the HW manual it says SWCLK is pulldown? 

I have soldered 2 boards now and got same issue on both so I don't think it is a soldering issue :/

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