in sdk_config.h it says this
// <e> NRFX_UART_ENABLED - nrfx_uart - UART peripheral driver //========================================================== #ifndef NRFX_UART_ENABLED #define NRFX_UART_ENABLED 1 #endif // <o> NRFX_UART0_ENABLED - Enable UART0 instance #ifndef NRFX_UART0_ENABLED #define NRFX_UART0_ENABLED 0 #endif