On Tue, 29 Jul 2014 07:37:44 +0200
Matthias Schwarzott <zzam@xxxxxxxxxx> wrote:
> On 23.07.2014 22:10, Antonio Ospite wrote:
> > On Wed, 23 Jul 2014 21:03:14 +0200
> > Matthias Schwarzott <zzam@xxxxxxxxxx> wrote:
> >
> > [...]
> >> The crc value:
> >> It protects the content of the file until it is in the demod - so
> >> calculating it on my own would only check if the data is correctly
> >> transferred from the driver into the chip.
> >> But for this I needed to know the algorithm and which data is
> >> checksummed exactly.
> >>
> >> Are the different algorithms for CRC values that give 16 bit of output?
> >>
> >
> > You could try jacksum[1] and see if any algorithm it supports
> > gives you the expected result, there is a handful of 16 bits ones:
> >
> > jacksum -a all -F "#ALGONAME{i} = #CHECKSUM{i}" payload.bin
> >
> Hi Antonio,
>
> I tried jacksum on the complete firmware and on parts - but it never
> matched the results from the chip.
>
> I now found out, that the crc register changes after every 32bit write
> to the data register - the fw control registers do not affect it.
>
> So I can try what crc results from writing 32bit portions of data.
> But even that did not help in guessing the algorithm, because I do not
> want to do 100s of experiments.
>
> some of my experiments:
> crc=0x0000, data=0x00000000 -> crc=0x0000
> crc=0x0000, data=0x00000001 -> crc=0x1021
> crc=0x0000, data=0x00000002 -> crc=0x2042
> crc=0x0000, data=0x00000004 -> crc=0x4084
> crc=0x0000, data=0x00000008 -> crc=0x8108
> crc=0x0000, data=0x00000010 -> crc=0x1231
>
> Is there some systematic way to get the formula?
I don't know much about crc, but the values you are getting look like
the entries in the table in lib/crc-itu-t.c so maybe compare the crc
you are getting with the ones calculated with crc_itu_t() from
include/linux/crc-itu-t.h
I just did a quick test with jacksum, the crc-itu-t parameters can
be expressed like this:
jacksum -x -a crc:16,1021,0,false,false,0 -q 00000010
and the output is the expected 0x1231 for the 0x00000010 sequence.
[...]
Ciao,
Antonio
--
Antonio Ospite
http://ao2.it
A: Because it messes up the order in which people normally read text.
See http://en.wikipedia.org/wiki/Posting_style
Q: Why is top-posting such a bad thing?
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