Stlink 2-1 Connection problem.

[IAgui]

I am going crazy! I am working with an STM32f745 and I am having SWD connection issues. I have a STlink 2-1 jumpered using the header connection from it over to my board Now, a interesting thing is happening when I probe the SWDCLK and SWIDIO line with a scope the connection is happy. When I take the probes off connection stops working. Please any ideas?

[Uwe Bonnes]

Missing or insuffienetn ground wires?

[IAgui]

Thank for your reply/ I have verified that my grounds are connected together between both boards and still the same problem/ Anything else I could try?

[mromani]

I have the same problem working with a RAK3172 module using two different stlink programmers and with two different custom board designs.

It sometimes work with lower speeds, sometimes with 4000Khz but I always have to connect a probe to the SWCLK line and another probe to GND, even if there is no tester at the other side of the probes (just a piece or wire!).

I tried different boards, modules, usb cables, power sources with the same results.

Did you find the solution? Any ideas?