https://devzone.nordicsemi.com/f/nordic-q-a/43465/uicr-serial-number-dfu-compatibility-sdk-15-2Using softdevice 6.1.0 and SDK 15.2: Is it safe to use NRF_UICR-&gt;CUSTOMER[0] through CUSTOMER[5] for storing serial numbers? It seems through in previous versions of SDK/SD/DFU some of these UICR registers were used for doing DFU. Thanks, Jeffen-USTelligent Community 13Fri, 08 Feb 2019 15:57:53 GMThttps://devzone.nordicsemi.com/thread/170169?ContentTypeID=1Fri, 08 Feb 2019 15:57:53 GMT137ad170-7792-4731-bb38-c0d22fbe4515:6910c579-84b6-4e61-82bc-47062e5fcb90Nguyen Hoan Hoang<p>You can use CUSTOMER with DFU no problem.&nbsp;</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/170133?ContentTypeID=1Fri, 08 Feb 2019 13:46:30 GMT137ad170-7792-4731-bb38-c0d22fbe4515:cd5a5ee6-4bd1-40a5-88ab-0ea29cbe74ecJeffW<p>Andreas,</p> <p>Thanks for the response. I was intending to program UICR at factory.<br />Looking at compiled hex images, it seems like DFU uses UICR-&gt;NRFFW, and not the CUSTOMER specific bits.<br />Please let me know if my conclusion is wrong.&nbsp;<br />Thanks,<br />Jeff</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/170068?ContentTypeID=1Fri, 08 Feb 2019 09:14:00 GMT137ad170-7792-4731-bb38-c0d22fbe4515:802edc17-2257-43ab-a21f-f01d2ac0a3e3AndreasF<p>Hi.</p> <p>As long as the SoftDevice is enabled, it&#39;s not possible to write to UICR. Ref<a href="https://www.nordicsemi.com/DocLib/Content/SoftDevice_Spec/s140/latest/SDS/s1xx/sd_resource_reqs/hw_block_interrupt_vector"> [0]</a>,<a href="https://www.nordicsemi.com/DocLib/Content/Product_Spec/nRF52840/latest/uicr"> [1]</a></p> <p>You can write if you have disabled the SoftDevice.</p> <p>Best regards,</p> <p>Andreas</p><div style="clear:both;"></div>