Basic firmware that demonstrates UART TX and RX using nRF9160DK (TX Pin: P0.01; RX Pin: P0.00).
Build with nrf9160dk_nrf9160_ns.
This has been tested with an nRF7002DK (the nRF7002DK must run different firmware), wired like so (ignore the LED strip that is also wired to the nRF7002DK).
NOTE: THE IMAGE IS WRONG. CHANGE P0.16 TO P0.17 AND CHANGE P0.15 TO P0.16
Open a serial terminal (115200 baud) for each DK to see the outputs.