How can I use DFU with peripherals/blinky?

[gfmoore]

I have flashed DFU OTA bootlaoder to my nRF82540 DK. (C:\nRF5_SDK_17.0.2_d674dde\examples\dfu\secure_bootloader\pca10056_s140_ble_debug)

It shows the two LEDs 1 and 2.

I can flash ble_blinky. It shows LEDs 1 and 3 when flashing. It works.

BUT So I can get some understanding of what is going on I would like to flash plain old blink to the device using the OTA.

I change the blink *.ld file from

MEMORY
{
FLASH (rx) : ORIGIN = 0x1000, LENGTH = 0xff000
RAM (rwx) : ORIGIN = 0x20000008, LENGTH = 0x3fff8
}

to

MEMORY
{
FLASH (rx) : ORIGIN = 0x27000, LENGTH = 0xff000
RAM (rwx) : ORIGIN = 0x20000008, LENGTH = 0x3fff8
}

So that the application is now above the softdevice. It all looks fine, but it doesn't work.

So how do things work. I'm assuming that somewhere there is a jump to the address where the blinky app is loaded (at 0x27000?) and then blinky runs.

I'm guessing that my ignorance is going to give me a heart attack at some point. 

Is there a document that explains for newbies how all of this hangs together?

Gordon

(In my research I've seen references to a define for APPLICATION_START_ADDRESS or something similar, but I can't find it. It may have been an old sdk?)

Here is my memory map

[gfmoore]

No, can't duplicate getting blinky to flash across now. I keep getting: Upload failed, invalid object.

[gfmoore]

Done it again. i.e. flashed the application part of blinky.

I think I was using SES for the OTA DFU and it mustn't have had access to the correct public key. I don't know how to check where it gets the public key from in Segger. So Iused my VS Code version.

Did turn on with button 4 to get into DFU mode and I flashed the same blinky app again (using --debug-mode). It all seems good.