need DFU description explanations

RE: need DFU description explanations

Somesh Burkule — Mon, 30 Dec 2019 09:09:37 GMT

[quote userid="26388" url="~/f/nordic-q-a/30311/need-dfu-description-explanations/120140"]That example is wrong, in fact. A PRN value 0x0100 means decimal 1, not decimal 256[/quote]

Please confirm. the following image shows its decimal 256.

RE: need DFU description explanations

ivansanchez — Tue, 13 Feb 2018 11:55:05 GMT

Please do not ask a new question in a reply. It's better to open a new question, and remember to explain as best as possible where those bytes appear, and when (what DFU commands have been sent before?).

RE: need DFU description explanations

amicus — Tue, 13 Feb 2018 10:38:24 GMT

I have one additional question according DFU start packets sending. I've found something strange. COuld You explain me please what's happen?

I'm trying to send:
nrfutil dfu serial -pkg d:\nRF5_SDK_14.2.0_17b948a\examples\dfu\secure_dfu_test_images\serial\nrf52832\ble_app_buttonless_dfu_without_bonds_s132.zip -p COM14

and sniffing on serial port and found hexadeciomal bytes:
C0 D1 4E 01 E0 03 00 00 00 04 00 00 00 00 00 00 00 00 00 00 00 FC 9D 00 00 7C 45 C0

I read DFU documentation from here:
infocenter.nordicsemi.com/index.jsp

I don't found 0xD1 in second byte and other bytes. What does it mean this hexadecimal bytes?
C0 in begining and end is SLIP protocol markers this point I understand bytes what means other bytes I totaly not understand.

Maybe I in wrong way and don't understand main DFU things..

Wait for comments!

RE: need DFU description explanations

amicus — Wed, 07 Feb 2018 15:32:28 GMT

I think it's a logical to have all value field in one (little endian) format. But of cause another talk when we talk about CRC field.

Thank You, for fast help!

RE: need DFU description explanations

ivansanchez — Wed, 07 Feb 2018 15:20:17 GMT

What I should believe? Example or description?

I suggest you base your implementation in the already existing reference implementation: pc-nrfutil. See https://github.com/NordicSemiconductor/pc-nrfutil/tree/master/nordicsemi/dfu

In examples I see is big endian format (PRN number is 02 01 00 - it means 256) but in description is mentioned little endian format ("Value (uint16, little endian) ")

That example is wrong, in fact. A PRN value 0x0100 means decimal 1, not decimal 256.

Refer to https://github.com/NordicSemiconductor/pc-nrfutil/blob/7f20bb89b1df082990c94bc58ceb26393fe52341/nordicsemi/dfu/dfu_transport_serial.py#L299, it looks like:

    def __set_prn(self):
        self.dfu_adapter.send_message([DfuTransportSerial.OP_CODE['SetPRN']]
        + map(ord, struct.pack('<H', self.prn)))

If you check https://docs.python.org/2/library/struct.html#byte-order-size-and-alignment , you'll see that

struct.pack('<H', self.prn)

means that PRN is a little-endian unsigned short (16-bit) integer. The same goes for all other fields involved in the DFU procedure, you'll find similar struct.pack() calls.

If I remember correctly, some of the metadata (in particular the crc32 hashes and sha256 hashes) might be in big-endian due to libraries used to calculate those values. Please be aware that you should check those separately.