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Strange SWDIO/SWCLK waveforms when trying to connect STM32F407VG

Question asked by novak.marek.001 on Jul 17, 2013
Hello,
I am making a project with STM32F407. I have a development board EasyMx PRO v7 from Mikroelektronika. When I am trying to connect (through SWD) the STM32F407 present on the board, there is no problem, the SWCLK (SWDIO looks the same) waveform is relatively good:
Exported image from scope: http://www.mnhs.cz/internalmcu.bmp

But when I soldered another STM32F407 on an empty LQFP100 adapter, connected VBAT, VDDA, VREF+ and VDD1-VDD6 to 3V3, VSS1-VSS4 and BOOT0 to GND, put the 100n capacitors over all the VDD and VSS lines, put the 2u2 capacitors to VCAP1 and VCAP2 and finally connected the SWDIO, SWCLK and NRST lines to programmer, it did not communicate with the microcontroller. So I inspected if the SWDIO and SWCLK lines are OK. Unfortunately, I got this strange waveform (SWCLK):
Exported image from scope: http://www.mnhs.cz/externalmcu.bmp

Later on, I discovered that the SWDIO and SWCLK lines are stuck at 1.4 volts all the time, does not matter the NRST is pulled high or low.

I am a novice to STM32 microcontrollers, maybe I forgot about some basic stuff.

Thank you very much for your help,
Marek.

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