DFU get started switch to DFU MODE

[achraf]

Im working with nrf52832 alone without dk ,  and sdk15.0.0 and SES
 i followd the tutorial of DFU mode : https://devzone.nordicsemi.com/nordic/nordic-blog/b/blog/posts/getting-started-with-nordics-secure-dfu-bootloader#h21sjziaqedvq7246h1tdi5lxp57zry
but in the step  Update new application firmware. i dont know how to switch dfu mode.
first i run the project secure_bootloadre_ble_s132_pca10040 , and Debug (go) it works i update to prkect via dfu , and restart to my application, but to go back to dfu another time, i dont know how to do it I should add a dfu service to my project ?? how ?? or there is some reset button or what please help me 

[achraf]

Thanks a lot Mr Edvin,
it works for me as you said I modified my bootloader project. and it works , now I'll see how to add a restart button to my application our w poweroff poweron, cause for the moment I shoud unplug and plug the alimentation .

otherwise I want to try your suggestion the buttonless_dfu example, but it doesnt work , i pick up the example of SDK15.0.0 cause Im working on it, with the nrf52832 is it because or ram or what , here is the picture of the segger results:

here is how it begin it seems everythin okey , this the image before the execution:

here is the image of the error:

here is the error above :

and the source of the error:

if its possible to help with the button ,and the butonless , it will be great , otherwise nor probleme , the main thing it works