I am trying to power a Nucleo-F042K6 from the external +5V only, i.e. without USB connected since my code is completed and fully functionnal. According to the user manual this shoud be possible and the only limitation is that the ST-LINK must be connected after.
However the F042K6 will not start because its NRST is kept low (at arount 1.2V), probably clamped by the protection diodes of the ST-LINK which does not have any power.
I suppose I could remove SB9 but then I'm afraid of losing some ST-LINK capabilities if I want to re-flash my code.
Am I missing something in the user manual? SB9 is only mentioned if we want to power the board with 3.3V.
Thanks to all.