SDK12 secure bootloader dfu missing upate service

Question

Hi,
I'am tring to test the dfu by secure bootloader.I had done all steps like: Test the BLE Secure DFU Bootloader application by performing the following steps .But I found out the bootloader didn't have the update service, when I connect it.What did I miss?

bjorn-spockeli · Accepted Answer

Issue 1: Missing DFU Service 
 Solution: You have to update the nRF Connect app, Secure DFU was added in the v4.4.x version and the current version is v4.8.1. You can see the features the latest version on Google Play, here is the link. 
 Issue 2: DFU fails after generating package with the following command (or similar)
nrfutil pkg generate --hw-version 1 --sd-req 0x80 --application-version 4 --application app.hex --key-file key.pem app_dfu_package.zip 
 Solution: Incorrect hardware version used , it should be 51 for the nRF51822 and not 1 as shown in the nrfutil documentation.