https://devzone.nordicsemi.com/f/nordic-q-a/112867/undefined-reference-to-bootmode_sethello I am studying DFU with reference to the Academy. Exercise 1 - DFU over UART - Nordic Developer Academy (nordicsemi.com) SampleCode of Exercise1 use McuBoot and McuBoot use Button2 to enter Serial Recovery mode. I want to enter Serial Recoveryen-USTelligent Community 13Wed, 17 Jul 2024 02:25:04 GMThttps://devzone.nordicsemi.com/thread/494256?ContentTypeID=1Wed, 17 Jul 2024 02:25:04 GMT137ad170-7792-4731-bb38-c0d22fbe4515:fb573ec8-3381-42cd-abe9-8ae3fa73331byama789<p>Hello, Vidar Berg.<br /><br />I mistaked setting above CONFIG to some config files.<br />Now, I can use tetention.<br />Thank you.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/493390?ContentTypeID=1Thu, 11 Jul 2024 11:48:47 GMT137ad170-7792-4731-bb38-c0d22fbe4515:8c3bd679-b4f2-4fe6-8c29-80918595589cVidar Berg<p>Hello,</p> <p>The retention system must also be enabled in the parent image for the&nbsp;bootmode_set() function to become available to the app. Does it build if you add the following settings to your prj.conf file:</p> <div> <div><span>CONFIG_RETENTION</span><span>=y</span></div> <div><span>CONFIG_RETAINED_MEM</span><span>=y</span></div> <div><span>CONFIG_RETAINED_MEM_ZEPHYR_RAM</span><span>=y</span></div> <div><span>CONFIG_RETENTION_BOOT_MODE</span><span>=y</span></div> <div><span></span></div> <div><span>?</span></div> <div><span>Best regards,</span></div> <div><span>Vidar</span></div> </div><div style="clear:both;"></div>