nRF52840 custom PCB firmware does not execute after power-cycle unless J-Link/RTT is attachedhttps://devzone.nordicsemi.com/f/nordic-q-a/127722/nrf52840-custom-pcb-firmware-does-not-execute-after-power-cycle-unless-j-link-rtt-is-attachedHardware: Custom PCB, nRF52840 SoC VDD = 1.8V (battery-powered, no USB) External LFCLK crystal (32.768 kHz) originally configured; switched to RC oscillator during debugging SDK / Toolchain: nRF Connect SDK v3.2.1 (Zephyr 4.2.99) Zephyren-USTelligent Community 13Thu, 09 Apr 2026 18:19:44 GMTRE: nRF52840 custom PCB firmware does not execute after power-cycle unless J-Link/RTT is attachedhttps://devzone.nordicsemi.com/thread/564740?ContentTypeID=1Thu, 09 Apr 2026 18:19:44 GMT137ad170-7792-4731-bb38-c0d22fbe4515:292b0761-2e4b-4486-8f5d-499ea60af903Ahmed0<p>I solved my issue. I had my pcb configured to be in 1.8V mode but&nbsp; the LDO was still enabled.&nbsp;<br /><br /><pre class="ui-code" data-mode="text">Put this in your device overlay file to disable regulator LDO: #include &lt;zephyr/dt-bindings/regulator/nrf5x.h&gt; &amp;reg1 { regulator-initial-mode = &lt;NRF5X_REG_MODE_LDO&gt;; }; </pre></p> <p></p> <p>For anybody else stumbling onto this forum post, here is another forum post with similar issues but&nbsp; their problem was different, it might help if my post hasnt:&nbsp;<a href="https://devzone.nordicsemi.com/f/nordic-q-a/64575/flashing-nrf52840-module#:~:text=nRFGo%20Studio%20is%20very%20old,I%20hope%20this%20helps">https://devzone.nordicsemi.com/f/nordic-q-a/64575/flashing-nrf52840-module#:~:text=nRFGo%20Studio%20is%20very%20old,I%20hope%20this%20helps</a>.</p><div style="clear:both;"></div>