I'm going crazy, look at the photos: if I move the SWD CLK connection in one point of the breadboard the connection works, in another it doesn't! The chip is a STM32L412KB, I tried to replace it but nothing! I also replaced the ST-LINK but nothing yet.

[APast.1]

[Tesla DeLorean]

Check the continuity

Check signal with scope ​

[GPerk.1]

Your STLink works. I have similar issue, on my L073 the StLink couldn't t connect. It was connecting and suddenly ST link interface stopped to work - on good few chips. St link was able to downlod the code in USART mode.

For me it is an issue with the chip - it is very sensitive.

Try following:

1. Ensure you StLink works on some other device.
2. Connect the uC via USART in boot mode

[Tesla DeLorean]

The CM0 parts want slower clocks on the SWD

[Piranha]

1. That is not a genuine ST-LINK, but a Chinese clone. Who knows how reliable it is...
2. The shorter path works, while the longer one with two additional connections doesn't - nothing crazy.
3. Try lower SWD frequencies.

[APast.1]

... Check the continuity

It's ok.

... Check signal with scope

It seems that the MC is not responding in the second position of the breadboard.

first:second:

 

[APast.1]

... Ensure you StLink works on some other device.

I tried another StLink, same behavior.

... Connect the uC via USART in boot mode.

I will try

[APast.1]

1. true
2. in reality if I keep the same length as in the second case but I change the final position in some cases it works. This drives me crazy :)
3. i tried up to 15 khz, nothing to do

[MM..1]

1. I mean you need connect under reset , but this clone dont have this prepared, need little change
2. your board have crazy connection remove it from universal and connect wires directly GND 3V3 SWCLK SWIO

[APast.1]

1. Could you please explain to me what these changes are?
2. unfortunately if I directly connect stlink to the MC it works but as soon as I connect the other pins to the breadboard it stops working