https://devzone.nordicsemi.com/f/nordic-q-a/59185/combining-softdevice-6-0-0-with-sdk-15-3Hi all Looking at the compatibility matrix, we understand that the following SoftDevices and SDK versions are compatible: SDK 15.0 &lt;---&gt; SoftDevice S140 6.0.0 SDK 15.3 &lt;---&gt; SoftDevice S140 6.1.1 We&#39;re currently developing firmware on SDK 15.3en-USTelligent Community 13Tue, 17 Mar 2020 16:17:37 GMThttps://devzone.nordicsemi.com/thread/240308?ContentTypeID=1Tue, 17 Mar 2020 16:17:37 GMT137ad170-7792-4731-bb38-c0d22fbe4515:c45303f1-89cf-4346-b742-2edeebe23ebbKenneth<p>It should work yes, though not tested.&nbsp;</p> <p>Best regards,<br />Kenneth</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/240294?ContentTypeID=1Tue, 17 Mar 2020 15:12:49 GMT137ad170-7792-4731-bb38-c0d22fbe4515:f2cc8f2f-9416-4bc2-98c7-c9ccbf53d2f1Ingo<p>Thank you Kenneth. I understand that using SD v6.1.1 is the preferred option. Yet, SD 6.0.0 is still compatible with SDK 15.3. Is that correct? We may not be able to switch to SD 6.1.1.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/240286?ContentTypeID=1Tue, 17 Mar 2020 14:34:44 GMT137ad170-7792-4731-bb38-c0d22fbe4515:d0f46405-edb9-4281-8567-d2ef1be491bcKenneth[quote user=""]Alternatively we could also use SoftDevice 6.1.1 if it is compatible with SDK 15.0.[/quote] <p>This is the preferred option, since you will get the latest softdevice fixes. Simply program the v6.1.1 softdevice, update&nbsp;to the v6.1.1&nbsp;softdevice header files in the application, and re-compile the application code. This will work for nRF5 SDK v15.0 yes.</p> <p>Best regards,<br />Kenneth</p><div style="clear:both;"></div>