Booting application from custom bootloader

[AntonHellbe]

Hi,

I'm currently developing a custom bootloader for DFU, using I2C.

The bootloader is based upon the secure UART bootloader for nRF52832. Transferring and writing the image works fine, I receive the entire image and write it at the start address 0x26000 (Softdevice is present). To boot the application I currently use nrf_bootloader_app_start(), however that doesn't seem to want to start the application. Do I need to change the start address for the nrf_bootloader_app_start? Currently it uses 0x00001000 (MBR).

Edit: An additional question, is it possible to flash the nRF52832 using a Motorola Srecord hex file? I've tried looking for any documentation of which .hex files that nrfjprog accepts but cannot find any.

HW: nRF52832 PCA10040 devkit

SDK: v15.3

SD: 6.1.1

[Vidar Berg]

I don't think you have to have to include a settings page. An alternative is to always calculate the app CRC on boot. If the check fails, you can just let the bootloader fall back to DFU mode.

I guess the question is then where it's best to store the CRC. I encountered a fairly similar project in a project where I was trying to add DFU support without having a dedicated bootloader. I ended up appending a 32 bit CRC at the end of the app image to avoid having to allocate a settings page in flash. 

ble_app_beacon_w_dfu.zip

[AntonHellbe]

That's a nifty solution, something I will most likely use.

One thing I've noticed is that in order to boot the application (after a succesful image transfer) I always have to reset an additional time on the devkit before the application boots. It seems like the NVIC_Systemreset() is not doing the trick after the image is flashed.

Any thoughts what could be the cause?

[Vidar Berg]

Do you know what the device is doing when it doesn't boot the app? Maybe it went back to DFU mode inside the bootloader, or got stuck in a fault handler? You can run "nrfjprog --readregs" to find out where the program is running at.

[AntonHellbe]

I've been trying to find out what's going on but it seems like it might hit a fault handler?

After receiving and image, verifying its CRC and writing it to memory the nRF52832 goes unresponsive for about 30-45 seconds. When I try to read the registers nrfjprog only returns:

ERROR: JLinkARM DLL reported an error. Try again. If error condition                                              
ERROR: persists, run the same command again with argument --log, contact Nordic                                   
ERROR: Semiconductor and provide the generated log.log file to them. 

After 30 seconds or so I can read the registers

R0:   0x01000001
R1:   0x40020518
R2:   0xE000E100
R3:   0x20002585
R4:   0x200000C0
R5:   0x00000000
R6:   0xE000E000
R7:   0x00000000
R8:   0x00000000
R9:   0x00000000
R10:  0x20000000
R11:  0x00000000
R12:  0x00000000
SP:   0x2000FF38
LR:   0x00015CCD
PC:   0x00015CCE
xPSR: 0x61000000
MSP:  0x2000FF38
PSP:  0x00000000

And the application is running.

Edit: Seems like it can take up to a minute or two. During this period I cannot connect to the nRF52832 using JLinkExe and I get disconnected when I boot the image:

****** Error: Communication timed out: Requested 12 bytes, received 0 bytes !

[AntonHellbe]

I hit a fault handler when I tried to uninit fsstorage, resolved by waiting until it was not busy anymore. Now the app boots instantly :).