Put Nrf52 in Vootload mode

[Shimon_nohayo]

Hi,

I'm usgn Nrf528332, Softdevice s132_nrf52_6.1.0_softdevice

I Use secure_bootloader BLE secure_bootloader\pca10040_ble with the public key, and matched privet Ket I generate DFU Zip file 

With Nrf Studio I burn SD and Bootloader

I use Nef connect to upload the DFU file - with Sucess

When I want to switch back to DFU target mode I use the following code

static void bootloader_start(void)
{
// A "simple" reset is not enough, the SD and IRQs must be disabled first
// uint32_t err_code;
const uint8_t ENTER_BOOTLOADER = 0xB1;

// err_code =
ble_conn_params_stop();
__sd_nvic_irq_disable();
NRF_POWER->GPREGRET = ENTER_BOOTLOADER;
NVIC_SystemReset();
}

For some reason, this MSU stay in teh App and not switch to DFU mode 

Please elaborate on what am I doing wrong.

Shimon

[Shimon_nohayo]

Hi,

I believe I found the reason for thsi issue but I don't know how to solve it.

The power regulator on the board is enabled by one of the NRF52 GPIOs, when the device reset itself the board the GPIO goes low (or floating) and the board is turned off.

If I try to enter to bootloader mode, and during that holds the power push button of the board - the process successes, but if the board is power off during the reset the process files

Please advise how can I deal with this issue

[Hung Bui]

Hi Shimon, 

Have you tried to add the code to configure and set the GPIO pin inside the bootloader ? 

If you already configured that and still it's not quick enough, you may need to consider to put a capacitor on the pin to hold it when the chip is switching between the application and the bootloader. 

[Shimon_nohayo]

Hi,

I did, I set the GPIO to '1' in the bootloader code.

If I understand correctly, the nRf52 perform reset and then it replaces the App with the Bootloader?

Is it possible to perform that without using the NVIC_SystemReset(); ?

I can not add a capacitor - there must be a method to overcome this issue. 

[Hung Bui]

Hi Shimon, 

Actually there is a trick to overcome this. By spec, when you do a softreset the GPIO will be reset (back to input no buffer connected)  but not with waking up from System OFF.  When you reset by waking up from system OFF the GPIO is preserved. 
You can have a look at this similar case.

[Shimon_nohayo]

Thank you,

Your idea solved the issue!