https://devzone.nordicsemi.com/f/nordic-q-a/12294/dualbank-to-singlebank-via-ble-dfuI currently have a dualbank bootloader setup and I&#39;m trying to change it to singlebank. If I burn the singlebank bootloader with the jlink it works fine, but if I use the old dualbank bootloader to update itself to the new singlebank hex, then it doesnen-USTelligent Community 13Sun, 06 Mar 2016 18:51:39 GMThttps://devzone.nordicsemi.com/thread/46487?ContentTypeID=1Sun, 06 Mar 2016 18:51:39 GMT137ad170-7792-4731-bb38-c0d22fbe4515:56ddbd90-17c0-4743-afab-ef620bbe3e54UncleGravity<p>Nevermind, I found the problem. I had not looked into the return values of SD_MBR_COMMAND_COMPARE. It works now! I changed the code in my question to show the working code.</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/46486?ContentTypeID=1Sun, 06 Mar 2016 18:13:07 GMT137ad170-7792-4731-bb38-c0d22fbe4515:93aee701-835f-4d7a-bbf2-7b1bb28a7e8bUncleGravity<p>Thanks for the quick reply, Vidar. I edited the original question with my attempt at modifying dfu_bl_image_validate() but it still doesn&#39;t work. Perhaps I misunderstood your answer. Am I missing something?</p><div style="clear:both;"></div>https://devzone.nordicsemi.com/thread/46485?ContentTypeID=1Thu, 03 Mar 2016 13:32:02 GMT137ad170-7792-4731-bb38-c0d22fbe4515:8fd7c309-21d8-4bb7-be6b-4ebcf4daa54eVidar Berg<p>Hi,</p> <p>The problem with updating the bootloader from dual- to single bank through bootloader DFU is that the new bootloader expects swap to be at the start of BANK0, while it&#39;s actually loaded to BANK1 by the old bootloader. What happens then is that the new bootloader updates itself with whatever data located in BANK0 using the MBR.</p> <p>The fix is to modify the dfu_bl_image_validate() function in dfu_single_bank.c run verification on both addresses (BANK0 and BANK1). This stops the dfu_bl_image_swap() function from being called twice.</p><div style="clear:both;"></div>