ST-LINK Utility give "Can not connect to target!" error. STM32f407vgt6 mcu and st-link can not connect.

[Iyesi.1]

I am struggling with debugging of STM32f407VGT6 mcu. I use discovery board as ST-LINK for debugging. Done below instructions:

-       All connections between st-link and uC

-       Power distribution controls (VCC, GND)

-       CN3 jumpers not connect

Shortly, all hardware instructions have done. But I see below problem:

I have tried lots of combinations of the settings like:

SWD-FrequenciesNormal - Hot plug - Connect under reset -(Low,high power modes)- Reset modes.

Also, NRST pin to ground and debugging simultaneously. But do not working every situation. Can you help me, please?

[Tesla DeLorean]

This can occur if your design is not actually functional.

​

Share a portion of schematic showing pin connectivity to STM32

​

Make sure VDDA is powered, that you have caps on VCAP pins and you see 1.25V there.​

[Iyesi.1]

Tesla DeLorean, thank you very much. Now I can connect to uC. "Make sure VDDA is powered, that you have caps on VCAP pins and you see 1.25V there.​" this was very helpful for me.

[Vangelis Fortounas]

Hello

be aware that VCC does not feed power to your board but takes the voltage from board to optimize the flashing algorithm

So the board must be allready powered when you try to connect to it