https://test-devzone.nordicsemi.com/f/nordic-q-a/88650/segger-embedded-studio-use-mutexHi. I am developing the nrf52832 seger embedded studio. I tried to use mutex using nrf_mtx.h, but there was an error. I don&#39;t know why this error is coming out. Help me. (Also, I know the definition of the mutex function, but I don&#39;t knowen-USTelligent Community 13 Non-ProductionTue, 07 Jun 2022 12:25:14 GMThttps://test-devzone.nordicsemi.com/thread/371138?ContentTypeID=1Tue, 07 Jun 2022 12:25:14 GMT137ad170-7792-4731-bb38-c0d22fbe4515:b3996a57-771c-46a3-ae5a-ca02b2f6a9c2user14926<p>Hi,</p> <p>I see you have declared test_mutex as &quot;extern&quot;, did you implement the variable in another file? The extern keyword tells the compiler that the symbol is defined elsewhere, and allows you to access global variables from multiple source files.&nbsp;</p> <p>See&nbsp;<a title="nRF Mutex" href="https://infocenter.nordicsemi.com/topic/sdk_nrf5_v17.1.0/group__nrf__mtx.html?cp=8_1_6_10_35">nRF Mutex</a>&nbsp;for description of the library and APIs.</p> <p>Best regards,<br />Jørgen</p><div style="clear:both;"></div>