what are the required steps/files/definitions/commands to get RTT output from a custom app into RTT Viewer ?

Question

I am using an nRF chip and the nRF SDK for 1st time and I think I am still at the steep part of the learning curve.

My problem is that I cannot get the log from my custom app in RTT Viewer. I use:

custom PCB with Taiyo Yuden EYSKBNZWB/nRF52840 Wireless Module
SDK 17.0.2
arm gcc 10.3.1
J-Link RTT Viewer V7.52b (JLinkRTTViewerExe)
nRF5_SDK/examples/peripheral/template_project

In my main.c source file I have included the following headers: https://infocenter.nordicsemi.com/index.jsp?topic=%2Fcom.nordic.infocenter.sdk5.v15.2.0%2Flib_nrf_log.html

#include "nrf_log_ctrl.h"
#include "nrf_log_default_backends.h"
#include "nrf_log.h"

Again in the main.c source file, I have the define - https://devzone.nordicsemi.com/f/nordic-q-a/29977/undefined-reference-to-nrf_log_default_backend_init

#define NRF_LOG_BACKEND_RTT_ENABLED 1

In the Makefile @ nRF5_SDK/examples/peripheral/template_project/pca10056/blank/armgcc I added the following line:

$(SDK_ROOT)/components/libraries/log/src/nrf_log_default_backends.c \

in order to solve the linker issue: main.c: undefined reference to `nrf_log_default_backends_init'

In the sdk_config.h file @ nRF5_SDK/examples/peripheral/template_project/pca10056/blank/config I have the follwoing settings:

#define NRF_LOG_ENABLED 1 // 0
#define NRF_LOG_DEFERRED 0 // 1
#define NRF_LOG_DEFAULT_LEVEL 3
#define NRF_FPRINTF_FLAG_AUTOMATIC_CR_ON_LF_ENABLED 0 // 1
last one from: https://devzone.nordicsemi.com/f/nordic-q-a/46685/no-log-output-to-debug-terminal-in-ses-or-rtt-viewer

The contents of my main.s source file are:

int main ( void ) {
    ret_code_t err_code = NRF_LOG_INIT ( NULL );
    APP_ERROR_CHECK ( err_code );
    NRF_LOG_DEFAULT_BACKENDS_INIT ();
    
    while ( true ) {
        uint32_t i ;

        for ( i = 0; i < 10; i++ ) {
            NRF_LOG_INFO ( "i = %u\r\n", i );
        }
    }
}

I thought that I could see some numbers printed in RTT VIewer but unfortunately I still can't manage to get the RTT output into the RTT Viewer after reading several posts so I would ask for help at this point. Any would be highly appreciated :-)

P.S. I think the connection PC <-> J-Link <-> PCB works fine as I managed to get an LED blink ca. every second.

Simonr · Accepted Answer

Hi again

I just ran the temperature project on my end to see if I could replicate it, and I see the "Temperature example started" message every time I press the reset pin on my DK. How exactly do you reset your device on your end?

What's necessary to enable the RTT backend on any example should be adding the following defines in sdk_config.h

// <e> NRF_LOG_ENABLED - nrf_log - Logger
//==========================================================
#ifndef NRF_LOG_ENABLED
#define NRF_LOG_ENABLED 1
#endif

// <h> nRF_Log 

//==========================================================
// <e> NRF_LOG_BACKEND_RTT_ENABLED - nrf_log_backend_rtt - Log RTT backend
//==========================================================
#ifndef NRF_LOG_BACKEND_RTT_ENABLED
#define NRF_LOG_BACKEND_RTT_ENABLED 1
#endif
// <o> NRF_LOG_BACKEND_RTT_TEMP_BUFFER_SIZE - Size of buffer for partially processed strings. 
// <i> Size of the buffer is a trade-off between RAM usage and processing.
// <i> if buffer is smaller then strings will often be fragmented.
// <i> It is recommended to use size which will fit typical log and only the
// <i> longer one will be fragmented.

#ifndef NRF_LOG_BACKEND_RTT_TEMP_BUFFER_SIZE
#define NRF_LOG_BACKEND_RTT_TEMP_BUFFER_SIZE 64
#endif

// <o> NRF_LOG_BACKEND_RTT_TX_RETRY_DELAY_MS - Period before retrying writing to RTT 
#ifndef NRF_LOG_BACKEND_RTT_TX_RETRY_DELAY_MS
#define NRF_LOG_BACKEND_RTT_TX_RETRY_DELAY_MS 1
#endif

// <o> NRF_LOG_BACKEND_RTT_TX_RETRY_CNT - Writing to RTT retries. 
// <i> If RTT fails to accept any new data after retries
// <i> module assumes that host is not active and on next
// <i> request it will perform only one write attempt.
// <i> On successful writing, module assumes that host is active
// <i> and scheme with retry is applied again.

#ifndef NRF_LOG_BACKEND_RTT_TX_RETRY_CNT
#define NRF_LOG_BACKEND_RTT_TX_RETRY_CNT 3
#endif

// </e>

// <h> nRF_Segger_RTT 

//==========================================================
// <h> segger_rtt - SEGGER RTT

//==========================================================
// <o> SEGGER_RTT_CONFIG_BUFFER_SIZE_UP - Size of upstream buffer. 
// <i> Note that either @ref NRF_LOG_BACKEND_RTT_OUTPUT_BUFFER_SIZE
// <i> or this value is actually used. It depends on which one is bigger.

#ifndef SEGGER_RTT_CONFIG_BUFFER_SIZE_UP
#define SEGGER_RTT_CONFIG_BUFFER_SIZE_UP 512
#endif

// <o> SEGGER_RTT_CONFIG_MAX_NUM_UP_BUFFERS - Maximum number of upstream buffers. 
#ifndef SEGGER_RTT_CONFIG_MAX_NUM_UP_BUFFERS
#define SEGGER_RTT_CONFIG_MAX_NUM_UP_BUFFERS 2
#endif

// <o> SEGGER_RTT_CONFIG_BUFFER_SIZE_DOWN - Size of downstream buffer. 
#ifndef SEGGER_RTT_CONFIG_BUFFER_SIZE_DOWN
#define SEGGER_RTT_CONFIG_BUFFER_SIZE_DOWN 16
#endif

// <o> SEGGER_RTT_CONFIG_MAX_NUM_DOWN_BUFFERS - Maximum number of downstream buffers. 
#ifndef SEGGER_RTT_CONFIG_MAX_NUM_DOWN_BUFFERS
#define SEGGER_RTT_CONFIG_MAX_NUM_DOWN_BUFFERS 2
#endif

// <o> SEGGER_RTT_CONFIG_DEFAULT_MODE  - RTT behavior if the buffer is full.
 

// <i> The following modes are supported:
// <i> - SKIP  - Do not block, output nothing.
// <i> - TRIM  - Do not block, output as much as fits.
// <i> - BLOCK - Wait until there is space in the buffer.
// <0=> SKIP 
// <1=> TRIM 
// <2=> BLOCK_IF_FIFO_FULL 

#ifndef SEGGER_RTT_CONFIG_DEFAULT_MODE
#define SEGGER_RTT_CONFIG_DEFAULT_MODE 0
#endif

You'll also have to add the nrf_log_backend_rtt.h/.c and SEGGER_RTT.h/ .c files to the project.

Best regards,

Simon

what are the required steps/files/definitions/commands to get RTT output from a custom app into RTT Viewer ?

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