NRF_LOG_INFO and printf

[nrf_user]

I'd like to both use printf and NRF_LOG in my application. However, I have not been able to get both working simultaneously. Is this possible?

I init the logging like:

ret_code_t err_code = NRF_LOG_INIT(NULL);
APP_ERROR_CHECK(err_code);

NRF_LOG_DEFAULT_BACKENDS_INIT();

Which completes, however after I init the uart for printf

uint32_t err_code;
app_uart_comm_params_t const comm_params =
{
.rx_pin_no = RX_PIN_NUMBER,
.tx_pin_no = TX_PIN_NUMBER,
.rts_pin_no = RTS_PIN_NUMBER,
.cts_pin_no = CTS_PIN_NUMBER,
.flow_control = APP_UART_FLOW_CONTROL_DISABLED,
.use_parity = false,
.baud_rate = NRF_UARTE_BAUDRATE_115200
};

APP_UART_FIFO_INIT(&comm_params,
UART_RX_BUF_SIZE,
UART_TX_BUF_SIZE,
uart_event_handle,
APP_IRQ_PRIORITY_LOWEST,
err_code);

I get an error code 8 "NRF_ERROR_INVALID_STATE" which seems to come from nrfx_uarte_init. Could anyone point out to me how to init uart such that I can use both printf and NRF_LOG?

[Susheel Nuguru]

They do not seem to work together as printf uses retarget.c file which uses app_uart library and NRF_LOG uses its own usage of nrf_drv_uart directly. Could be a conflict in both usage if retarget and NRF_LOG are working on the same instance of the uart.

[nrf_user]

Thank you, that makes sense.

Do you have any suggestions for how to nrf log to uart while also being able to write directly to uart?

[Susheel Nuguru]

i would suggest you to use NRF_LOG even for everything to have a consistent behavior. Trying to access uart directly without NRF_LOG knowing might cause unpredictable behavior since NRF_LOG buffers the logs before flushing.