https://devzone.nordicsemi.com/f/nordic-q-a/127074/failed-to-use-channel-sounding-mode-3Hello Support Team, I am currently working on Channel Sounding with the nRF54L15 devkit, and I am encountering an issue when using main_mode . Until now, I was using the default configuration BT_CONN_LE_CS_MAIN_MODE_2 , and I decided to try MODE 3en-USTelligent Community 13Thu, 19 Feb 2026 12:29:26 GMThttps://devzone.nordicsemi.com/thread/561592?ContentTypeID=1Thu, 19 Feb 2026 12:29:26 GMT137ad170-7792-4731-bb38-c0d22fbe4515:18eba473-4e47-4911-89d7-9a5f3dbb029dSwRa<p>Hi Harmel,</p> <p>I see that you have added the following:</p> <p>.main_mode_type = BT_CONN_LE_CS_MAIN_MODE_3,<br />.sub_mode_type = BT_CONN_LE_CS_SUB_MODE_1,</p> <p>This is not a valid combination of main mode and sub mode types.. See here:&nbsp;<a href="https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-62/out/en/low-energy-controller/channel-sounding.html#UUID-5bd41abf-c6ad-a020-d3cf-e6ad8434fc66_N1690580327249">https://www.bluetooth.com/wp-content/uploads/Files/Specification/HTML/Core-62/out/en/low-energy-controller/channel-sounding.html#UUID-5bd41abf-c6ad-a020-d3cf-e6ad8434fc66_N1690580327249</a>&nbsp;</p> <p>The valid combination to run step mode 3 is as follows:</p> <p><span>.main_mode_type = BT_CONN_LE_CS_MAIN_MODE_3,<br /> .sub_mode_type = BT_CONN_LE_CS_SUB_MODE_UNUSED</span></p> <p><span>Please see if that helps.</span></p> <p><span>Best Regards,</span></p> <p><span>Swathy</span></p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/561503?ContentTypeID=1Wed, 18 Feb 2026 14:47:52 GMT137ad170-7792-4731-bb38-c0d22fbe4515:8de70211-a9bd-49dc-8e82-492be2b683c2SwRa<p>Hi Harmel,</p> <p>Checking this now. Will get back to you with the updates.</p> <p>(Thanks for attaching the previous case as well. The case went into waiting list and skipped the queue to be resolved)</p> <p>Regards,</p> <p>Swathy</p><div style="clear:both;"></div>