using RTT console to print along with newlib C library in Zephyr

[Abdellah AF]

Hello everyone,
I am using NrfConnect with Zephyr on Segger embedded studio .
I want tu use the math logarithm function in my code and print the result on the debug terminal. At first when enabling the "Use RTT for console" configuration, printf works, then I wanted to add the math.h log function which gave me "Undefined reference to log" error.
To resolve the error I checked the "Newlib C library" configuration which made the log function work but then I realised the printf does not work anymore.
Printf does not throw any error but nothing is printed on the Debug terminal.
How can I use both log and printf with RTT console ?

OS: windows
Board: Nrf52DK
SDK: nrf Connect sdk v1.5.0
RTOS: Zephyr

[Håkon Alseth]

Hi,

 

Do you have CONFIG_RTT_CONSOLE=y set?

 

Kind regards,

Håkon

[Abdellah AF]

Yes it is set and printf works until I set "Newlib C library" then it no longer works

[Abdellah AF]

Yes the prj.conf is the same. Printf does not print to the debug terminal.

Then I removed CONFIG_NEWLIB_LIBC=y from prj.conf and printf worked but  math.h functions are no longer recognized

[Håkon Alseth]

Hi,

 

Could you test this on a newer ncs release to see if the issue is persistent across versions?

 

Kind regards,

Håkon

[Abdellah AF]

Hello,

Yes, the issue is persistent

Please find attached a test project

printfNewlib.rar

[Håkon Alseth]

Hi,

 

I can confirm that I see the same issue. Could you register this as an issue with the zephyr project github?

https://github.com/zephyrproject-rtos/zephyr/issues

 

Kind regards,

Håkon

[Abdellah AF]

Hi,

I posted on Github before coming here and they closed the post and told me that it was an nrf Connect sdk issue

[Håkon Alseth]

Hi,

 

I tested your project with upstream zephyr (v2.7.0-rc2), and it does not print over rtt using printf() there either. Switch to minimal libc, then it prints.

 

Kind regards,

Håkon