Have finished RIB king gate opener/controller based on NRF52840 & MySensors.
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@NeverDie a big thank you as I was inspired by many of your post and this was my first Nrf5 project. The backplate is designed in KiCAD and then outsourced for etching to one local semi-hobby service. Modules are then connected via precision header pins (concept inspired by Ardumower)

@omemanti @mfalkvidd Thank you, I think I did it. It works now - or I hope so from the code.

** Programming Finished **
** Verify Started **
nrf51.cpu: target state: halted
target halted due to breakpoint, current mode: Thread 
xPSR: 0x61000000 pc: 0x2000002e msp: 0x20004000
verified 1412 bytes in 0.038633s (35.692 KiB/s)
** Verified OK **
** Resetting Target **
shutdown command invoked

What I was confused is that there is erase sketch, but to make it erased there is this trick with burn bootloader. Still the port is greyed out, but it seems I am able to flash blank sketch. Thanks

Still valid in 2020. Got a compilation error "Error resolving FQBN: missing". Downgrade to 1.8.9 helped