bootloader_app_start vs NVIC_SystemReset();

[ToTo]

Hi, i want to jump from my app to the bootloader, i used the function

void bootloader_app_start(void)

{

    vMBt_eStopAdv_Exe() ;// Stoping the BLE ADV 
    sd_power_gpregret_clr(POWER_GPREGRET_GPREGRET_Msk); 
sd_power_gpregret_set(BOOTLOADER_DFU_START); 
sd_softdevice_disable(); 
interrupts_disable(); 
sd_softdevice_vector_table_base_set(NRF_UICR->BOOTLOADERADDR); 
bootloader_util_app_start(NRF_UICR->BOOTLOADERADDR);

}

and it's OK , but when i use NVIC_SystemReset(); instead of bootloader_util_app_start it dosen't work and the bootloader dosen't start. although i added in the script of the bootloader to enter the bootloader program if GPREGRET=BOOTLOADERADDR or GPREGRET=0x00 ( case of a reset is handled )

this the modfication in the bootloader code :

if (dfu_start || (!bootloader_app_is_valid(DFU_BANK_0_REGION_START)) ||NRF_POWER->GPREGRET == 0x00)... this the condition part to enter dfu_mode , i just added the case where GPREGRET=0x00

Remarks:

1- the initialisation of the softdevice is always done in the case of a reset because we have :

-static bool dfu_start = false;

• bool app_reset = (NRF_POWER->GPREGRET == BOOTLOADER_DFU_START);

• ble_stack_init(!app_reset );

2- no button check is included , i commented that part as follow

//dfu_start |= ((nrf_gpio_pin_read(BOOTLOADER_BUTTON_PIN) == 0) ? true: false);

Questions :

1. Why it dosen't work with the nvic reset ?
2. can you explain to me the process of jump ..i have a small idea about assembly code but i don't know what are the registers used there when jumping...(thread mode .. )
3. If i want to use Nvic_Reset() what should i do ? ( i don't care about the bonding service !! )
4. This function ( __asm static void bootloader_util_reset(uint32_t start_addr) , used for the jump) is really confusing me !! in fact it's invoking a parameter that it never uses ..any explanation please

[Hung Bui]

Hi Toto,

I could have suggested you to remove the if statement, but then we wouldn't know why it wouldn't work at the first place with your modification.

The main difference between hard reset and softreset is the retention registers will keep the value when you do soft reset. In this case it's GPREGRET register. Have you made sure you don't set GPREGRET to something else before you do softreset ?

Simply set the bootloader in debug mode and step in to the code can tell why it didn't work earlier.