I'm using the nRF52 DK with SDK 15.3.0. At this point I'm trying to get a UART loop back to work by tying the TX pin (P0.8) to the RX pin (P0.9). I have verified that the RX GPIO is set for an input and the input buffer is connected. My project is based on the "ble_app_uart" project. I see what looks like reasonable data going out on the TX pin but I never get the APP_UART_DATA_READY event in the event handler. I do get the APP_UART_TX_EMPTY event after sending the string of 4 bytes but do not get any other events. I have also tried putting a 50mS delay after sending a byte with "app_uart_put" then calling "app_uart_get" and it returns NRF_ERROR_NOT_FOUND indicating no data to read.
Looking at the UARTE0 registers after sending the data, EVENTS_RXSTARTED is a 1 and EVENTS_RXDRDY and EVENTS_ENDRX are both 0. The ENDRX interrupt is enabled, the RXD PTR is set to an address in RAM, the MAXCNT is 1 and AMOUNT is 0.
Here is my UART initialization code:
I get the same results with two nRF52 DK boards. Any ideas?