For Legacy DFU, what actually happens when the firmware is uploaded?

RE: For Legacy DFU, what actually happens when the firmware is uploaded?

Xander To — Sun, 11 May 2025 21:52:09 GMT

Hi Sigurd, the link is broken. Where can I find the same information to learn about?

Thanks,

Xander

RE: For Legacy DFU, what actually happens when the firmware is uploaded?

tjhasan — Wed, 18 Aug 2021 17:49:53 GMT

This is exactly what I was looking for. Thank you very much!

RE: For Legacy DFU, what actually happens when the firmware is uploaded?

Sigurd — Wed, 18 Aug 2021 17:32:58 GMT

Hi,

It's write commands, and 2 characteristics, DFU Packet and DFU Control Point. More information about that here:

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v11.0.0/bledfu_transport_bleprofile.html

https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v11.0.0/bledfu_transport_bleservice.html

RE: For Legacy DFU, what actually happens when the firmware is uploaded?

tjhasan — Wed, 18 Aug 2021 17:02:37 GMT

I understand that the firmware image is transferred, but my question specifically is how it is transferred. Is it done via simple write commands to a specific service / characteristic in the GATT table?

Given that the image is, as you say, "written to flash in chunks", can I assume that the contents of the .bin file to-be transferred is written to a specific service or characteristic in the GATT table?

The links you have provided show me a high level overview of the ble dfu process, but I'm looking for more of a low level implementation explanation.

RE: For Legacy DFU, what actually happens when the firmware is uploaded?

Sigurd — Wed, 18 Aug 2021 13:04:21 GMT

Hi,

The firmware image is transferred and written to flash in chunks/portions. There are also meta-data transferred, such as CRC and application version:
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v11.0.0/bledfu_example_init.html
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v11.0.0/bledfu_architecture_transfer.html
https://infocenter.nordicsemi.com/topic/com.nordic.infocenter.sdk5.v11.0.0/dfu_bootloader_state_machine_sec.html