Rerouting printf() to UART

[newUser]

Hi,

Currently our system is using printf() to print some debug messages to the Segger debug terminal.
Now we would like to reroute these messages to a UART port.

We are already using 1 UART for communication with chip on the board. We would like to use the other UART for the debug messages.

In our sdk_config.h we changed NRF_LOG_BACKEND_RTT_ENABLED from 1 to 0, and NRF_LOG_BACKEND_UART_ENABLED from 0 to 1.
Furthermore, we set NRF_LOG_BACKEND_UART_TX_PIN. For now, we left NRF_LOG_BACKEND_UART_BAUDRATE at 30801920

Unfortunately, after these changes the UART that we were previously already using successfully is no longer working.
This is coming into a conditional breakpoint:

    app_uart_comm_params_t const uart1_settings =
    {
        .rx_pin_no    = UART1_TX_PIN,
        .tx_pin_no    = UART1_RX_PIN,
        .rts_pin_no   = RTS_PIN_NUMBER,
        .cts_pin_no   = CTS_PIN_NUMBER,
        .flow_control = APP_UART_FLOW_CONTROL_DISABLED,
        .use_parity   = false,
        .baud_rate    = UART_BAUDRATE_BAUDRATE_Baud115200
    };
    APP_UART_FIFO_INIT(&uart1_settings,
                       UART_RX_BUF_SIZE,
                       UART_TX_BUF_SIZE,
                       uart1_event_handle,
                       APP_IRQ_PRIORITY_LOWEST,
                       err_code);
    APP_ERROR_CHECK(err_code);       // check if UART is setup without errors

What are we missing?

[Vidar Berg]

Hello,

Maybe both are trying to use the same UARTE instance? The Logger module  UART backend is hardcoded to use the UARTE0, same  instance as the app_uart library uses by default.

Please make sure APP_UART_DRIVER_INSTANCE is set to '1' in your sdk_config.h file. This will make APP_UART_FIFO_INIT() initialize UARTE1.

Best regards,

Vidar

[newUser]

Thank you Vidar Berg, this got us a bit further. We see all NRF_LOG messages going to UART now.
However, we would like printf() to go to UART too. 

What extra step do we need?

[Vidar Berg]

But instance 0 is used by the logger module. Could you not use the NRF_LOG_* macros instead of printfs then?

[newUser]

We started to use printf() because NRF_LOG_* did not print any text in the debug terminal.
To change all of printf in the source code takes a lot of time and has a huge impact on our source code.
This is why we prefer to reroute printf()

[Vidar Berg]

I see, but shouldn't it be quick and easy to replace the printf's with NRF_LOG_INFO or equivalent if you do a "search and replace" across your source files?

[newUser]

We have tried, but our Ubuntu colleague doesn't get any data to the debug terminal when using NRF_LOG_*. (RTT backend enabled and UART backend disabled in sdk_config).
For our Windows people, it works.

If we can get NRF_LOG_* to work on both Windows and Linux, we would like that very much. It would indeed solve all our problems.

Any ideas?

[Vidar Berg]

Does your Ubuntu colleague use an older version of Segger embedded studio by any chance? In that case, you may need to build with the 'NRF_FPRINTF_FLAG_AUTOMATIC_CR_ON_LF_ENABLED' setting disabled in sdk_config

Issue with RTT logs not being displayed in SES debug terminal: https://devzone.nordicsemi.com/f/nordic-q-a/45985/nrf_log-not-working-on-segger-embedded-studio/182742#182742