https://devzone.nordicsemi.com/f/nordic-q-a/18520/undefined-symbol-problem-app_uart_getI&#39;m sorry for this easy question. I&#39;m just starting to develop an application using a nrf52832. I want to use uart functions, so I added a line #include &quot;app_uart.h&quot;. But when I build the source, it failed saying &quot;._build\nrf52832_xxaa.axf: Erroren-USTelligent Community 13Wed, 21 Dec 2016 09:03:36 GMThttps://devzone.nordicsemi.com/thread/71463?ContentTypeID=1Wed, 21 Dec 2016 09:03:36 GMT137ad170-7792-4731-bb38-c0d22fbe4515:60c209cb-37d1-49d9-9888-7c2c2d066e06Sigurd<p>Hi,</p> <p>You also need to configure the <code>sdk_config.h</code> file.</p> <p>You will need to have these defines:</p> <pre><code>#define APP_UART_ENABLED 1 #define APP_FIFO_ENABLED 1 #define APP_UART_DRIVER_INSTANCE 0 </code></pre> <p>If you want to use printf(), you also need <code>#define RETARGET_ENABLED 1</code></p> <p>If you use Keil, I recommend to use the &quot;Configuration Wizard&quot;</p> <p><img src="https://devzone.nordicsemi.com/cfs-file/__key/communityserver-discussions-components-files/4/6114.ConfigurationWizard.png" alt="image description" /></p> <p>You can enter the wizard at the bottom of the editor when you have sdk_config.h open. You can than quickly edit the sdk_config.h using this GUI wizard:</p> <p><img src="https://devzone.nordicsemi.com/cfs-file/__key/communityserver-discussions-components-files/4/configwizuart.png" alt="image description" /></p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/71462?ContentTypeID=1Wed, 21 Dec 2016 08:43:12 GMT137ad170-7792-4731-bb38-c0d22fbe4515:dccd6816-9911-4a51-b4ea-ae85ae6d98a5Alex<p>Have you added &quot;app_uart.c&quot; to your project?</p><div style="clear:both;"></div>