Bootloader Jump to Main application crashes after modifying RAM_START address from 0x20002300 to anything else

[rishi]

Hi there...

I am using :

Device :Custom board using nrf52840 (fanstel module BT840)

SDK : nRF5_SDK_17.0.2

SoftDevice : S140 7.2.0

In order to add DFU capability on our product, I started with pca10056_usb_debug secure bootloader, first tested it on dev board (PCA10056) with ble blinky application everything works fine as expected. Then ported usb bootloader to our custom board and updating ble blinky application  works ok.

When i try to flash our real application, DFU process finishes successfully after BL reboots and tries to jump to our real application there it crashes (it never enters the main function of application).

The only difference in ble blinky and our real application is the application size and RAM_START setting which is 0x20002300 in blinky app but 0x20002bf0 in our real application.

I am wondering if i need to modify some setting in boot loader in order to compensate this RAM_START modification?

But my understanding is the way control flows is as follows :

If BL is present :

MBR->BL>SoftDevice->Application.

else if there is no BL:

MBR>SoftDevice->Application.

So basically Softdevice knows how to jump to main application as i can run/debug my real application without BL in the picture.

And as i understand the BL functioning it always calls the Softdevice (0x1000) and then its SD responsibility to jump to main application.

So why this RAM_START is an issue for Bootloader?

Will appreciate any help/ pointers to documentation which clarify this question...

Thanks a lot!

[Henry_Chou]

Because the RAM start address is overlap with your softdevice memory. So that the system can't work normal. So the SD application notes is mention that the ROM start addrress for each version(Code size fixed). But the RAM start address should be depends on your ble service resource in SD(RAM size not fixed depend on service UUID counts ,w/r characteristic ,central & peripheral numbers).

[rishi]

Thanks for your response. But then how come system works normal without boot loader if my application address is overlapping with soft device memory.

So is there a way to overcome this issue if i want to use a boot loader or to configure say SD with different application RAM START address? 

[Henry_Chou]

I know.The BL(Bootloader)  also will be used the memory. So that the application code start address should be larger than original one. But in my experience, the RTT log message(SDK) will show the memory (RAM) allocation. You just follow the rule and modify the mapping in  LD or project file is okay.

[rishi]

Thanks a lot Henry for your response.

Yes you are right RTT Logs showed me to modify the RAM Start address to 0x20002bf0 which i did in project settings and its working perfectly fine.

May be i am not explaining correctly! My Application independently(without BL) working fine no issues and i am using the RAM_START address= 0x20002BF0 as suggested by logs in the first run.

My issue is Bootloader which can not jump to my application after first upgrade.

Is there a way to tell boot loader application that our main application starts at 0x20002bf0 instead of 0x20002300 ?

 

[Henry_Chou]

If the boot loader is made coding by yourself, you can get the real memory size and add on the SD size. And you can get the application RAM start address. If not, it just can be try and error.

[rishi]

Yes i am coding the Boot loader and the application, i do not need to try and error i know for sure my application's start address.

My real question is where and how to modify the boot loader so that it can jump to my application correctly.

Application crashes after control is passed from jump_to_addr() function in nrf_bootloader_app_start_final.c