Need Help with CRC16

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Hi good day; I want to see the possibility that if someone can help me gene
rate a crc calculator from txt files, I have a text file, and the result of
 the crc by which it must be submitted I already have, but I don't know how
 to get to He actually has several files to do the test, but I couldn't get
 to those results; Can someone help me?

Re: Need Help with CRC16
On Monday, July 27, 2020 at 3:55:00 PM UTC-4, Miguel Angel Palos M wrote:
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nerate a crc calculator from txt files, I have a text file, and the result  
of the crc by which it must be submitted I already have, but I don't know h
ow to get to He actually has several files to do the test, but I couldn't g
et to those results; Can someone help me?

What is in the text file, the data you need to calculate the CRC16 on?  

Are you coding this in some particular language?  Can you give us some deta
ils?  

--  

  Rick C.

  - Get 1,000 miles of free Supercharging
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Re: Need Help with CRC16

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generate a crc calculator from txt files, I have a text file, and the resul
t of the crc by which it must be submitted I already have, but I don't know
 how to get to He actually has several files to do the test, but I couldn't
 get to those results; Can someone help me?
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ails?  
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Sure, the File is attached; I have a program that checks the value of the c
rc that is in the first line against the crc that gives the checksum of the
 file; so my purpose is to figure out how to modify the file and obviously  
put the new crc on the first line.

I do not know if I explained well?


--------------------Filetext begins-----------
E48D
8
   1
   1
   1
   400
8888
TH86
    9  
    8  
    7  
    6  
    3  
    2  
    1  
    0  
0
0
 0 0 0 0 0 0 0 0 0 0
 0 0 1 1 1 1 0 0 0 0
100
0
0
0
1
0
1
0 0 0 0 0 0
0
2
0
1
1
2
2
2 4
4 4
3
   120  
    6    1    20  
    1    55  
    200    1    999  
    1    999  
    0    0    0  
    0    0  
    300    1    999  
    1    999  
    0    0    0  
    0    0  
    3000    1    9000  
    1    9999  
    0    0    0  
    0    0  
    0    0    0  
    0    0  
    200    20    999  
    1    999  
    200    20    999  
    1    999  
    300    1    999  
    1    999  
    0    0    0  
    0    0  
    200    1    999  
    1    999  
    200    1    999  
    1    999  
654
        FALSE  
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
       TRUE  
  5  
    FIXED     XRAYS    1  500  400    0    0    NA    0  500
33   33   33   33   654  250  250  
    FIXED     XRAYS    1  100   80    0    0    NA    0  100
33   33   33   33   654  250  250  
    FIXED     XRAYS    1  100   80    0    0    NA    0  100
33   33   33   33   654  250  250  
      ARC     XRAYS    1  180   96 1800 2700    NA    0  180
33   33   33   33   654  100  100  
      ARC     XRAYS    1   90   53 2700 1800    NA    0   90
33   33   33   33   654  100  100  
--------------------------file text end-----------------------------

Re: Need Help with CRC16
On 28/07/2020 03:57, Miguel Angel Palos M wrote:

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Do you have any documentation or information about the file format or
the way the CRC is calculated?

As I see it, there are two key challenges.  First, there are a large
number of variations as to what "CRC16" could mean.  The Wikipedia
article can give you some idea - there are lots of suitable polynomials
for 16-bit CRC's, you can have any starting value, there can be bit
reversals, byte reversals, and other variations.

<https://en.wikipedia.org/wiki/Cyclic_redundancy_check

The biggest question, I think, is knowing what part of the file the CRC
is run over, and in what way.  Obviously the first line is not part of
the checksummed data, since it contains the CRC.  Which other parts are
omitted?  Are the numbers used directly as 16-bit values?  Are ASCII
characters used as the data?  Is white space skipped or included?  Line
endings?

No one here can tell you (unless someone happens to recognize the file
format).  Trying to figure out the variation used by guesswork and trial
and error is going to be a lot of effort.


Re: Need Help with CRC16
On 7/27/2020 12:54 PM, Miguel Angel Palos M wrote:
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Why don't you ask "him" for clarification?


Re: Need Help with CRC16

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esult  
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ow  
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n't  
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To this day I already know the polynomial of the crc16, any other idea of  
??how to obtain the other data that I lack to calculate the
 data of the crc?

Re: Need Help with CRC16
:

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e  
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 result  
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know  
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ldn't  
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 ??how to obtain the other data that I lack to calculate th
e data of the crc?

I thought that was all you needed???  

--  

  Rick C.

  -++ Get 1,000 miles of free Supercharging
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Re: Need Help with CRC16
On 7/29/2020 4:46 PM, Miguel Angel Palos M wrote:

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Why don't you ask "him" for clarification?



Re: Need Help with CRC16
On 30.7.20 2.46, Miguel Angel Palos M wrote:

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In the Internet RFC 1662 <https://tools.ietf.org/html/rfc1662 part C,  
there is a pretty general example of calculating CRCs. The PPP  
polynomial is different from the IBM CRC-16, but the algorithm is valid  
for it, too, if the polynomial is adjusted in a suitable way.

--  

-TV

Re: Need Help with CRC16
On 30.7.20 2.46, Miguel Angel Palos M wrote:

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At least, you need the initial value of the generator and which way the  
bits are processed, most significant end first or least significant end
first.

If you have many examples, the initial value can be deduced, but it  
would be better to know it. Often all ones (0xffff) are used, to prevent  
initial null bytes of the message being ignored. Sometimes the final  
value is inverted.

The example text file cannot be reliably used to check, as its  
whitespace can be transformed during transfers through the NNTP protocol.

--  

-TV

Re: Need Help with CRC16
On 7/30/2020 1:15 AM, Tauno Voipio wrote:
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You also don't know if the CRC is calculated over the actual text file
*or* if the text file is a pretty-printed version of the data (stored
in some not defined encoding) that the checksum protects.

Are line terminations CRs?  LFs?  CRFLs?

Sure seems like the *source* of the file would be best equipped to
indicate what the "rules" are!

Re: Need Help with CRC16

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ce can  
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In fact, when modifying even a blank space the program that validates the c
rc, marks an error; if you take into account the blank spaces.

The Line terminations are a new line /n

the source files are published,  
and the rest is an executable (exe) that only verifies it and then executes
.


Re: Need Help with CRC16
On 7/30/2020 6:46 AM, Miguel Angel Palos M wrote:

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"source files"?  As in "source code" (for the program)?
If so, then you already have what you need.

Otherwise, try removing the first line from the file and feeding
the balance to <https://crccalc.com/ to see what *it* computes
as the checksum.  If it agrees with the value in the line that
you removed, then you (appear to) have a tool that will do
the work that you want.


Re: Need Help with CRC16
El jueves, 30 de julio de 2020 a las 3:15:40 UTC-5, Tauno Voipio escribi?
?:
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:  
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e  
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 result  
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know  
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ldn't  
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of ??how to obtain the other data that I lack to calculate  
the data of the crc?
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Mr Tauno Voipio


I have many examples of +10 files with the crc in the header which is what  
it should give and all in TXT format, the detail is that I have not even fo
und what you are commenting on and it makes itself look so easy.

----physics.txt-------
E48D
8
   1
   1
   1
   400
8888
TH86
    9  
    8  
    7  
    6  
    3  
    2  
    1  
    0  
0
0
 0 0 0 0 0 0 0 0 0 0
 0 0 1 1 1 1 0 0 0 0
100
0
0
0
1
0
1
0 0 0 0 0 0
0
2
0
1
1
2
2
2 4
4 4
3
   120  
    6    1    20  
    1    55  
    200    1    999  
    1    999  
    0    0    0  
    0    0  
    300    1    999  
    1    999  
    0    0    0  
    0    0  
    3000    1    9000  
    1    9999  
    0    0    0  
    0    0  
    0    0    0  
    0    0  
    200    20    999  
    1    999  
    200    20    999  
    1    999  
    300    1    999  
    1    999  
    0    0    0  
    0    0  
    200    1    999  
    1    999  
    200    1    999  
    1    999  
654
        FALSE  
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
               -1                  0
       TRUE  
  5  
    FIXED     XRAYS    1  500  400    0    0    NA    0  500
33   33   33   33   654  250  250  
    FIXED     XRAYS    1  100   80    0    0    NA    0  100
33   33   33   33   654  250  250  
    FIXED     XRAYS    1  100   80    0    0    NA    0  100
33   33   33   33   654  250  250  
      ARC     XRAYS    1  180   96 1800 2700    NA    0  180
33   33   33   33   654  100  100  
      ARC     XRAYS    1   90   53 2700 1800    NA    0   90
33   33   33   33   654  100  100  
----physics.txt----ends



-----service.txt-----
EB78
 7
 0
 0
 100 5
 200 11
 200 0
 200 7
 200 5
 300 14
 462 5
 442 3
 -100 -3
 -100 -3
 -100 -3
 -100 -3
 -100 -4
 -100 -3
 0 0
 300 -2
 -1500 -3
 2100 1
 0 0
 -6 0
 76 0
 125 0
 -300 -14
 500 40
 200 5
 200 8
 510 77
 100 0
 0 0
 0 0
 -1500 600
 100 0
 100 0
 100 0
 100 0
 100 -1
 100 0
 100 0
 100 0
 100 0
 100 0
 100 0
 200 0
 200 0
 205 0
 200 0
 210 0
 195 0
 300 0
 100 0
 100 0
 100 0
 100 0
 100 0
 300 0
 100 0
 100 0
 100 0
 100 0
 0 0
 0 0
 0 0
 0 0
 100 0
 3650 -50 180 409 40 2048 -52 21 1024 1024 16
 7197 -32293 0 7194 -32290 0
 2750 850 200 409 512 12288 -52 32 1024 1024 16
 7214 18905 0 0 0 0
 201 -105 40 615 885 4096 52 0 1024 1024 6
 6 -4117 857 4 4095 1481
 201 -105 40 615 885 4096 52 0 1024 1024 6
 -5 -4098 482 -15 4125 586
 201 -20 40 615 864 8192 52 0 1024 1024 6
 366 1827 -406 0 0 0
 201 -20 40 615 864 8192 52 0 1024 1024 6
 348 1805 -285 0 0 0
 1675 595 64 307 200 0 -52 32 2047 102 8
 4646 9594 0 0 0 0
 1250 750 160 307 180 16384 52 40 683 300 8
 4009 4211 0 0 0 0
 1540 0 160 307 200 8192 52 40 683 400 8
 3185 12886 0 0 0 0
 2750 850 96 624 128 12288 -52 32 500 500 8
 7190 -20251 0 0 0 0
 402 5 40 615 0 0 52 0 1024 1024 1
 0 0 0 0 0 0
 402 5 60 615 384 0 52 0 1024 1024 8
 737 3683 439 0 0 0
 32
 20 20
 30 100
 842 6 -8 0 8196
 800 256 0 0 0
 3640 800 0 0 4096
 3640 800 0 0 4096
 2400 630 0 0 1280
 2400 800 0 0 1280
 2500 400 0 0 0
 1200 120 0 0 12288
 1000 110 0 0 10496
 1700 50 0 0 18176
 28 120
 20 100
 6 20
 6 20
 6 20
 6 20
 6 100
 6 100
 6 100
 20 120
 5 0 900 1800 2700 3600 0
 5 900 1350 1800 2250 2700 0
 6 -90 -40 20 80 140 190
 6 -90 -40 20 80 140 190
 5 -20 20 80 140 190 0
 5 -20 20 80 140 190 0
 6 650 800 1000 1200 1400 1600
 5 770 875 1000 1125 1230 0
 6 0 300 600 900 1200 1500
 5 900 1350 1800 2250 2700 0
 0 0 0 0 0 0 0
 5 20 100 200 300 380 0
 255
 0 1 1 1 2 3 4 5 6 6 7 8 9 10 11 12
 12 13 13 14 14 15 15 16 16 17 18 19 20 21 22 23
 23 25 28 32 36 40 40 40 40 40 40 40 40 40 40 40
 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40 40

---------service.txt---ends-------


Re: Need Help with CRC16
El jueves, 30 de julio de 2020 a las 8:40:53 UTC-5, Miguel Angel Palos M es

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?:  
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 me  
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he result  
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t know  
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ouldn't  
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a of ??how to obtain the other data that I lack to calculat
e the data of the crc?  
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t  
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l.  
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t it should give and all in TXT format, the detail is that I have not even  
found what you are commenting on and it makes itself look so easy.  
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The First Line in each file are the crc that should be.

Re: Need Help with CRC16
A bit of web searching will find sample code to do CRC16 for various processors.

--  
mdfs.net/Info/Comp/Comms/CRC16.htm

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