https://devzone.nordicsemi.com/f/nordic-q-a/4457/printf-app-trace-not-outputting-to-uartHi all, I am having a bit of a problem with the printf. I could not figure out what could be the problem. From what I search people seem to be getting it working with out any problem. I am using the SDK 6.1 and using it on kepler eclipse. I seten-USTelligent Community 13Fri, 14 Nov 2014 21:29:13 GMThttps://devzone.nordicsemi.com/thread/15831?ContentTypeID=1Fri, 14 Nov 2014 21:29:13 GMT137ad170-7792-4731-bb38-c0d22fbe4515:1f5cf5d7-5fd0-4d78-9231-c4980e8c12a7Chaiwat Sungkhobol<p>I was able to get the printf working on SDK 6.1 by adding the code below in app_trace.c</p> <pre><code>int _write(int fd, char * str, int len) { for (int i = 0; i &lt; len; i++) { simple_uart_put(str[i]); } return len; } </code></pre> <p>Found this code in <a href="https://github.com/hlnd/printf-gcc">https://github.com/hlnd/printf-gcc</a> and it work</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/15830?ContentTypeID=1Fri, 14 Nov 2014 07:33:21 GMT137ad170-7792-4731-bb38-c0d22fbe4515:3b6b571e-378c-468d-8569-38e32952d5b4Krzysztof Chruscinski<p>Hi,</p> <p>retarget in SDK 6.1 was ARM Keil only so printf&#39;s won&#39;t work in GCC. However it&#39;s fixed in SDK 7.0.1 which you can find at <a href="http://developer.nordicsemi.com">developer.nordicsemi.com</a>.</p><div style="clear:both;"></div>