On 07/29/2014 11:53 AM, Antonio Ospite wrote:
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.
maybe crc = crc + crc(val)
Antti
--
http://palosaari.fi/
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