nRF52840 Dongle Zephyr: Jump to DFU/bootloader (buttonless)

[Sasa Karanovic]

Hi,

I'm using nRF52840 dongle and nRF connect SDK 1.6.0 (Zephyr) to create a BLE HID + USB CDC device.
Is it possible to jump to bootloader from application code (or ideally have it triggered over USB by nrfutil)?

I understand that with old nRF SDK you would be able to use DFU library but looking trough the nRF Connect SDK, I can't find any reference
or examples on how to jump to bootloader without using buttons.

Is there a Zephyr configuration and/or library/module example available that shows how to do this?
If not, would it be possible to do it in a "hacky" way by modifying registers and instructing the MCU to jump to bootloader address?

edit: Just to clarify, I would like to use DFU feature over USB (not OTA).

Thanks,
Sasa

[Vidar Berg]

Hi,

It seems like the pull down on P0.19 is not strong enough to drive the reset line low. I suggest you configure P0.19 as an output instead.

Best regards,

Vidar

[vincenttc]

Hi,

My fault. The dongle can be reset after pull down GPIO on P0.19, but the dongle will not hold on bootloader (blinking red led) but enter app instead. Is this under expectation?

[Vidar Berg]

Hi,

I can't think of any obvious reasons for why it would exit DFU mode after a pin reset. Are you using the original pre-programmed bootloader on this dongle? And does it stay in DFU mode when you press the reset button?

[vincenttc]

Yes, I do not change the bootloader code and yes, the dongle will stay in DFU mode after press the reset button.
FYI, I am using ncs version 2.1.2 if helpful

[Vidar Berg]

Please try with the function below and see if you get the same result.

const struct device *gpio_dev = DEVICE_DT_GET(DT_NODELABEL(gpio0));

static inline void reset_to_bootloader()
{
    int err;
	err = gpio_pin_configure(gpio_dev, 19, GPIO_OUTPUT | GPIO_OUTPUT_INIT_LOW);
	if (err) {
		LOG_ERR("Failed to configure P0.19");
	}
}