DFU - what is "Init packet file" (*.dat) and how to get it?

[Jarmo]

I now have my app.hex and bootloader is running at nRF51822 and yet, the nRF Toolbox finds "DfuTarg" as expected. However, after selecting my file the UI surprisingly starts to ask about "Init packet" and I just say "NO", because I don't have such a thing anywhere.

Yep, right, the device firmware upload fails after that! Great. Two times it complained about missing init data or something, and two times the error was something else.

So, how to get that stupid .dat file there? And sorry, I am a bit frustrated after yet another fruitless day... complains removed

[Wojtek]

How to generate the INIT file for DFU?

Use method with nrfutility, as it is the most simple one.

[Wojtek]

MAster control panel (and android equivalents that are able to dfu ota) has been a bit retarded some time ago (i don't know if this is fixed in new version). The problem was that when you tried to do DFU OTA from app, it just restarted (jumped to bootloader), you received link loss and app became stupid at that moment. You had to scan again, connect to DfuTarg (device advertised in bootloader mode then) and repeat selecting OTA file, and update went good then. This also may be your issue...