Please help me solve this error

[xytan]

._build\nrf52832_xxaa.axf: Error: L6218E: Undefined symbol nrf_saadc_channel_init (referred from nrf_drv_saadc.o).

[RK]

That's just a basic, basic C linker error which is telling you you've used nrf_saadc_channel_init() but haven't included the source file which defines it in the build.

So add the correct .c file to your build, and since your next question will be 'what is the correct c file' it's drivers_nrf/hal/nrf_saadc.c