Cargo Features

NRF52 has no features set by default.

[dependencies]
nrf52 = { version = "0.4.1", features = ["rt"] }
rt

Enables device of cortex-m-rt ^0.5.1

Features from optional dependencies

In crates that don't use the dep: syntax, optional dependencies automatically become Cargo features. These features may have been created by mistake, and this functionality may be removed in the future.

cortex-m-rt rt?

Enables cortex-m-rt ^0.5.1