SEGGER RTT printf() problem

[DragonAnger]

Hi, I have problem with using printf() in SEGGER RTT.

I've read tutorial and others about SEGGER RTT printf() problem, but they didn't work.

When I use printf() in RTT and compile I got error like this:

[._build\nrf51422_xxac.axf: Error: L6218E: Undefined symbol SEGGER_RTT_printf (referred from main.o).]

And when I trying to see definition of printf() I got this.

Thanks for reading my question!

[Petter Myhre]

If you see the first sentence in the tutorial:

In SDK 12.0.0 or later, logging/debugging over RTT is built in to the logger module NRF_LOG. To enable logging over RTT, "check" the NRF_LOG_BACKEND_SERIAL_USES_RTT option in sdk_config.h in the configuration wizard.

It seems you are using SDK 12.3.0?

[DragonAnger]

Yes, I use SDK 12.3.0 and I didn't know about NRF_LOG_BACKEND_SERIAL_USES_RTT.

So I tried that but I got same error message.

Anyway, Thank you for your answer!

[Petter Myhre]

So which example are you using? Have you modified it any way?

[DragonAnger]

I'm using ble_app_uart. And I tested other example that I didn't modified anything, I got same problem. Is there other way to see error code? I cannot use usb.

Thank you for your answer!

[Petter Myhre]

I just took the unmodified ble_app_uart example from SDK 12.3.0 and I only modified NRF_LOG_BACKEND_SERIAL_USES_RTT. It compiles without any problem. Some other changes are required though. You need to disable logging with uart, include a couple of files in main.c and enabled the logging module. I have attached my project if you want to have a look.

Here is the project. Should be unzipped into examples\ble_peripheral