detailed example to create a custom bootloader?

[Abhishek]

Hello ,

following are my requirements :

1. to create a secure bootloader which checks app validity at every boot .
2. the boot loader should also accept UART communication .

following things i have tried :

1. Stripping the secure DFU bootloader exanple just to boot into my own application : a. compiling the strippred code(removed every aspect of appcheck and DFU via Bluetooth) b. added a blinky funtionality before jumping to the new address ( this is also not sure what address to jump to) c. flashed the bootloader as per given directions using nrfprog and IAR d. flashed the original blinky code (example with a different delay) using IAR

the expectation from this code is to first show the blinky with 100msec delay and then jump to my apop with the blinky with 500 msec delay ,

the result i get is that the blinky from my main application runs directly bypassing the bootloader , i have driven the APP_START_ADRESS as 0x1000

PLease help with a tutorial or a way to achieve my requirements.

board used : nrf52840 dk SDK : 13.00 alpha

[Hung Bui]

@Abhishek: How did you test ? If you only test your application with softdevice and no bootloader, then it not possible to start the application at other address unless you write a kind of bootloader at the normal application address (end of softdevice address).

If you have our bootloader, then it's possible to change address of your application. First you have to update your application setting to set the start address of your application. Second you need to modify the bootloader to update the "MAIN_APPLICATION_START_ADDR" to point to where you application start. Then you should be fine.