I purchased a module that I encountered during startup. At first I programmed the module via the ST link v2.
Example: E: \ nRF5_SDK_11.0.0_89a8197 \ examples \ peripheral \ blinky \ pca10028 \ s130 \ arm5_no_packs
before programming, Bluetooth was not visible to other devices. After programming, it was not visible to other devices
How can I get the chip back to factory settings with ST Link v2?
Because I feel the memory of the layout is messed up
For new development I recommend to get an nRF52-DK, the nRF52-DK also support programming and debugging of external hardware (provided that VDD is approx 3V) using the on-board SEGGER J-Link debug out header.
Then following the User Guide of the nRF52-DK to set it up and get started with nRF5 SDK.