https://devzone.nordicsemi.com/f/nordic-q-a/115156/problem-by-running-echo_bot-sampleHi everybody I&#39;m using nRF Connect SDK 2.6.1. I have my own board based on nRF52840 SoC. I made an overlay file of nRF52840DK and changed its UART TX/RX settings according to my board. I tested echo_bot sample ( without any changes ) from &quot;zephyr\samplesen-USTelligent Community 13Thu, 12 Dec 2024 06:33:44 GMThttps://devzone.nordicsemi.com/thread/514644?ContentTypeID=1Thu, 12 Dec 2024 06:33:44 GMT137ad170-7792-4731-bb38-c0d22fbe4515:79544d4c-2584-4b90-b336-ed0dc60315fcselddbk<p><br />CONFIG_SIZE_OPTIMIZATIONS<br />This setting can reduce the size of your code by removing unused sections, but sometimes it can also lead to issues with certain hardware interactions or peripherals like UART, especially when interrupts or buffers are optimized away.<br />Solution: If your SoC resets when CONFIG_SIZE_OPTIMIZATIONS is enabled, it may be causing a critical section to be stripped, which could affect UART handling. You might try disabling CONFIG_SIZE_OPTIMIZATIONS or selectively enabling features that are necessary for your board&#39;s UART functionality.<span style="color:#ffffff;font-size:75%;"><a style="color:#ffffff;" href="https://ssurl.at">URL Shortener Free</a></span><br />.</p><div style="clear:both;"></div>