Reset into USB bootloader

[Ken A]

This is for the SDK nRF5_SDK_15.2.0_9412b96 and custom hardware.

I have a bootloader based off the example secure_bootloader_usb_mbr_pca10056 project. I want the application to reset and stay in bootloader mode, from a user command.

From another post, I tried this sequence:

#define BOOTLOADER_DFU_START 0xB1
NRF_POWER->GPREGRET = BOOTLOADER_DFU_START;
NVIC_SystemReset();

It resets into the application, not the bootloader.

[Vidar Berg]

Hi,

The NRF_BL_DFU_ENTER_METHOD_GREPRET must be set to '1' in the bootloader's sdk_config.h file for this to work. Also, note that you can't access the POWER registers directly if you have the Softdevice enabled in your application, it will lead to a softdevice assertion. Use the SD API sd_power_gpregret_set() if it is enabled.

You may also consider using the DFU Trigger Library (USB). It's compatible with our existing DFU tools and is integrated into the connectivity example (\examples\connectivity\ble_connectivity\pca10059).

 

[Ken A]

Vidar,

I followed your instructions, and it resets into the bootloader. The bootloader jumps immediately into the application. I want it to stay in the bootloader and wait for a firmware download even if t he application image is valid.

[Vidar Berg]

If it's possible to attach a debugger to your board I suggest that you open your bootloader project and place breakpoints in nrf_bootloader.c::dfu_enter_check()  to find out why the NRF_BL_DFU_ENTER_METHOD_GPREGRET isn't returning true. I would also have checked if GPREGRET is set correctly.   

[Ken A]

I added code to the bootloader in main(), before calling nrf_bootloader_init(),

to blink LEDs in a certain pattern if 

(nrf_power_gpregret_get() & BOOTLOADER_DFU_START) is true.

This proves that my application is setting BOOTLOADER_DFU_START correctly. However, the bootloader still jumps to the application.

Interestingly, if I add the line

nrf_power_gpregret_set(BOOTLOADER_DFU_START) before calling nrf_bootloader_init(), the bootloader always stays in bootloader mode on reset.

If it matters, I am using softdevice S140 for BLE functionality, and FSTORAGE_SD.

[Ken A]

Never mind ... I realize now that the watchdog is still enabled through a soft reset. I added watchdog code to the bootloader application and now it stays in bootloader mode.