Not able to enter to DFU mode sometimes

RE: Not able to enter to DFU mode sometimes

Hung Bui — Thu, 01 Feb 2024 13:12:40 GMT

Hi,
I don't think it could be, especially if it works for most of devices and that you don't write to the GPREGRET in your application for other purpose.

RE: Not able to enter to DFU mode sometimes

aniskane — Thu, 01 Feb 2024 12:44:10 GMT

Hi Hung,

Thanks for your feedback. It seems that GPREGRET is not cleared before writing it. Could this be the culprit?

Br,

Antti

RE: Not able to enter to DFU mode sometimes

Hung Bui — Thu, 01 Feb 2024 12:29:48 GMT

Hi Antti,

I assume you have cleared the GPREGRET before writing. The same as what we did in ble_dfu_buttonless_bootloader_start_finalize() function.

There could be a chance that the device may not be able to retain in DFU mode when you switch from the application. If the power supply doesn't sustainable for the bootloader to run and enter DFU mode, if there is a reset before the bootloader can enter DFU then it will reset back to the application.
The same applied if you have WDT on the application and if you don't feed it quick enough in the bootloader, it may reset the bootloader before the bootloader can feed the WDT causing the device to boot back to the application.

It's important that when you receive the defect item, could you try to debug and check why it doesn't want to jump to bootloader. You can put a breakpoint at the beginning of the bootloader to check the value of GPREGRET before the bootloader start.

RE: Not able to enter to DFU mode sometimes

aniskane — Thu, 01 Feb 2024 10:48:15 GMT

Hi,

The SDK version is nRF5 SDK v15.2.0. I'm not sure about protocol used for DFU (original developer has left the company). To enter DFU mode these commands are issued:

// Enter DFU

sd_power_gpregret_set(0, 0xB1); // Set the retention register flag

NVIC_SystemReset(); // Soft reset. Device should boot in bootloader mode

I haven't been able to reproduce the issue myself but I've seen it happening.

Br,

Antti

RE: Not able to enter to DFU mode sometimes

Sigurd Hellesvik — Thu, 01 Feb 2024 10:03:39 GMT

Hi,

Which version SDK do you use?

hWhat is the protocol used for DFU?

How does the device normally enter DFU mode?

Have you been able to reproduce the issue on a test device?

Regards,
Sigurd Hellesvik