https://devzone.nordicsemi.com/f/nordic-q-a/64515/how-to-add-timer-in-nrf52840-sdk16-in-bootloaderHi I am test the DFU function in nRF52840. I want to add a timer to the bootloader to generate a one-second sleep action. But when even I have not started to use the timer just only add the &lt;app.timer.c&gt; and &lt;drv_rtc.c&gt; to the project and build successfullyen-USTelligent Community 13Wed, 05 Aug 2020 11:58:21 GMThttps://devzone.nordicsemi.com/thread/263208?ContentTypeID=1Wed, 05 Aug 2020 11:58:21 GMT137ad170-7792-4731-bb38-c0d22fbe4515:f0631bdb-f960-4ce7-abd5-2c56b158cef3Vidar Berg<p>Hi <span style="font-family:verdana, geneva;">Jonathan</span>,</p> <p>Are you building the bootloader with SES by chance? The flash_placement.xml file used by the bootloader is set-up so you don&#39;t get a linker error even if the bootloader starts to grow into the &quot;.mbr_params_page&quot;. section. This could potentially explain why it stopped working even if you just added the modules without using them. Here is the placement file from SDK 17.0.0 which should result in a linker error if the bootloader becomes too big : <a href="https://devzone.nordicsemi.com/cfs-file/__key/support-attachments/beef5d1b77644c448dabff31668f3a47-883ea208ac194404982cd474ab74e5f3/flash_5F00_placement.xml">devzone.nordicsemi.com/.../flash_5F00_placement.xml</a>. You may re-build the bootloader with this one to confirm if it actually is too big. A solution then is to reduce the bootloader start address (note: address must be flash page-aligned)</p> <p>The bootloader already has 2 timers, one to feed the Watchdog if enabled, and one inactivity timer to make the bootloader time out at some point, these are implemented in nrf_bootloader_dfu_timers.c with RTC2.</p> <p>Best regards,</p> <p>Vidar</p><div style="clear:both;"></div>