https://devzone.nordicsemi.com/f/nordic-q-a/33845/uart-interrupt-mode-undefined-behaviourHi! I&#39;m running UART example and modified to run upon interrupt and its working fine, but in main() if condition ( if (cr == &#39;q&#39; || cr == &#39;Q&#39;) ) is not executing even condition is satisfied and it is printing q/Q upon sending through serially but noten-USTelligent Community 13Thu, 26 Apr 2018 13:38:48 GMThttps://devzone.nordicsemi.com/thread/129982?ContentTypeID=1Thu, 26 Apr 2018 13:38:48 GMT137ad170-7792-4731-bb38-c0d22fbe4515:0046b21d-ee69-4578-b631-3213d3bf2144Carl Richard<p>Hey!<br /><br />It should work if you change the definition of <strong>data</strong>&nbsp;from <em>static</em> to <em>volatile</em>&nbsp;as the value of <strong>data</strong>&nbsp;can be changed at any given time. Though be aware that the interrupt only handles inputs character by character so that&nbsp;<strong>data</strong>&#39;s resulting value after writing for example &#39;q&#39; is &#39;\n&#39; (Newline). As the last character of the input is &#39;\n&#39; (Newline).</p> <p>I still got it to work with &#39;q&#39; and &#39;Q&#39;, but there could be limitations.</p> <p>- Carl Richard</p><div style="clear:both;"></div>