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'[EE] Change CRC in bin file'
2008\07\13@150237 by Tomás Ó hÉilidhe

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I'm trying to upload some custom firmware to my router but it won't
accept the firmware file because the CRC check is wrong in it.

What I did was I downloaded a legitimate ".bin" file from the router
manufacturer and then edited it myself with a hex editor, but I don't
know how to go about changing the CRC.

Anyone know?

2008\07\13@171849 by olin piclist

face picon face
Tomás Ó hÉilidhe wrote:
> I'm trying to upload some custom firmware to my router but it won't
> accept the firmware file because the CRC check is wrong in it.
>
> What I did was I downloaded a legitimate ".bin" file from the router
> manufacturer and then edited it myself with a hex editor, but I don't
> know how to go about changing the CRC.

Shouldn't this be OT or maybe TECH?


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\13@185558 by Jinx

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> > I'm trying to upload some custom firmware to my router but it won't
> > accept the firmware file because the CRC check is wrong in it.

> Shouldn't this be OT or maybe TECH?

Bob, you having lunch ? ;-)


2008\07\13@192343 by Apptech

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>> What I did was I downloaded a legitimate ".bin" file from
>> the router
>> manufacturer and then edited it myself with a hex editor,
>> but I don't
>> know how to go about changing the CRC.

> Shouldn't this be OT or maybe TECH?

Maybe.
But I don't think that noising up the channel with "wrong
label" material for the next short while is liable to be
overly useful.

[TECH] is brand spanking new, numbers using it is certain to
be lower than steady-state at present and so it is liable to
be a black hole for many people for now. (And long term for
those who wish it to be).

Under the old system I'd see this as more [EE] than [OT] so
EE seems good to me for now.



           Russell

2008\07\13@194703 by Bob Blick

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Jinx wrote:
>>> I'm trying to upload some custom firmware to my router but it won't
>>> accept the firmware file because the CRC check is wrong in it.
>
>> Shouldn't this be OT or maybe TECH?
>
> Bob, you having lunch ? ;-)

I should be, eh?

I've got a lot on my plate today, so I'll address this generally now and
in more detail later.

If you don't like a post, please ignore it. If it really bothers you,
send me an email directly.

If you start a thread, do your homework and post a quality message.

Although I think CRC is a valid [EE] topic, the quality of the original
post was extremely low. There's tons of information about router
firmware already on the web so there will definitely be information
addressing this specifically.

If the original post had even included something as basic as the
router's model number, it would have doubled the value of the post. We
need to increase the quality of the posts.

Please don't be a nanny, just ignore posts you don't like, OK? Thanks.

Cheerful regards,

Bob

2008\07\13@201755 by Cedric Chang

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You will have to find out what kind of "CRC" is used.  There is no  
standard "CRC" algorithm.  There are literally thousands of CRC  
methods in use.
cc


On Jul 13, 2008, at 1:02 PM, Tomás Ó hÉilidhe wrote:


I'm trying to upload some custom firmware to my router but it won't
accept the firmware file because the CRC check is wrong in it.

What I did was I downloaded a legitimate ".bin" file from the router
manufacturer and then edited it myself with a hex editor, but I don't
know how to go about changing the CRC.

Anyone know?

2008\07\14@072615 by sergio masci

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part 1 1401 bytes content-type:TEXT/PLAIN; charset=UTF-8 (decoded quoted-printable)



On Sun, 13 Jul 2008, Cedric Chang wrote:

> You will have to find out what kind of "CRC" is used.  There is no  > standard "CRC" algorithm.  There are literally thousands of CRC  > methods in use.
> cc

The CRC algorithm is pretty standard (the only real variations being start with all zeros, all ones, use 16 bit, 24 bit or 32 bit accumulator), it's the polynomial that tends to vary. Even so there are CCITT standard polynomials.

> > > On Jul 13, 2008, at 1:02 PM, Tomás Ó hÉilidhe wrote:
> > > I'm trying to upload some custom firmware to my router but it won't
> accept the firmware file because the CRC check is wrong in it.
> > What I did was I downloaded a legitimate ".bin" file from the router
> manufacturer and then edited it myself with a hex editor, but I don't
> know how to go about changing the CRC.
> > Anyone know?

A little bit of experimentaion should reveal the answer quite quickly. Start by trying to generate the same CRC supplied in the original ".bin" file using the standard CRC alogorithm and different polynomials. If it's a 16 bit polynomial you could try a brute force (all combinations of 16 bits) within a few minutes on a modern PC. I suspect 32 bits wouldn't take more than a few hours.

Regards
Sergio Masci

part 2 35 bytes content-type:text/plain; charset="us-ascii"
(decoded 7bit)

2008\07\14@073721 by olin piclist

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Apptech wrote:
> Under the old system I'd see this as more [EE] than [OT] so
> EE seems good to me for now.

Right, but we're under the new systems now.  I guess I really don't
understand the new definition of EE if this is valid EE.


********************************************************************
Embed Inc, Littleton Massachusetts, http://www.embedinc.com/products
(978) 742-9014.  Gold level PIC consultants since 2000.

2008\07\14@075346 by Tamas Rudnai

face picon face
I guess it is not TECH nor EE as I do not think it is anything to do with
engineering:

> [EE]
> The doing of Electrical/Electronic Engineering that you can do
> yourself. Power stations go into TECH unless it's a power station that
> you can build. So too eg Magnetohydrodynamics etc. Windmill
> alternators and related systems and alternate energy at the doing
> level go into EE. Windfarms into TECH. etc

It is rather a hacking, so I suppose should go to OT:

> [OT]
> This label is for posts that are completely off the topic of
> engineering/technology. The only things we don't ever want to see are
> religious/metaphysical, sex, hate, or political messages.

But I do not mind to be honest, I just ignore this completely as I am not
completely sure if that is legal to modify someone's code in any how and I
am not going to contribute for this.

Tamas



On Mon, Jul 14, 2008 at 12:39 PM, Olin Lathrop <spam_OUTolin_piclistTakeThisOuTspamembedinc.com>
wrote:

{Quote hidden}

> -

2008\07\14@080658 by Apptech

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>> Under the old system I'd see this as more [EE] than [OT]
>> so
>> EE seems good to me for now.

> Right, but we're under the new systems now.

If you are not just trolling then I suggest that you reread
what I wrote to see how it addresses your point.

There is no reason that the change to a new system need be a
legalistic sudden change. Common sense suggests that it be
allowed to be a process that people can to adapt to. While
this halcyon honeymoon phase can't be expected to last
indefinitely, expecting people to post to a new tag when,
due to the normal processes of list operation,  many people
will not yet be aware the tag exists or have made a decision
whether to subscribe to it, means that you would be
requiring people to operate a largely "write only" system
for no good reason.

> I guess I really don't
> understand the new definition of EE if this is valid EE.

As above
The suggestion was that a 'grace period' should reasonably
apply until people have had a reasonable chance to adapt to
the changes.


       Russell








2008\07\14@095545 by Bob Ammerman

picon face
Okay,

I agree this isn't EE

I hate to suggest another topic, but...

Many on the PICLIST are primarily EE types, designing hardware, and the
firmware is extras....

Many others on the PICLIST are primarily programmer types, writing firmware
and hooking into hardware (which they may have designed)

We have an EE tag so the EE types can ask about non-PIC but EE related
concepts.

Do we need an SE (software engineering) tag so that programmer types have a
place to ask about non-PIC but programming related topics?

Being one of the programmer types I don't want to be a second class citizen
on the list!!

-- Bob Ammerman
RAm Systems

2008\07\14@102415 by Apptech

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> I hate to suggest another topic, but...

...

> Do we need an SE (software engineering) tag so that
> programmer types have a
> place to ask about non-PIC but programming related topics?
>
> Being one of the programmer types I don't want to be a
> second class citizen
> on the list!!

I'd assume that at present it belonged in OT or TECH.
What say we see how the new TECH tag settles down and how
happy people are with content.
While I agree that a SE / SOFT / SOFTWARE / ...  or whatever
tag would naturally accommodate many subjects, it took years
to get the TECH tag and there was strong resistance to it. I
imagine that proposing another new tag at this stage would
cause the long term admins to blow a fuse :-). For now I
would be happy enough to see such in TECH and we can see
what the populace who subscribe think after a while.


       Russell


2008\07\14@111836 by Bob Ammerman

picon face
My issue is this:

An EE doesn't have to deal with TECH: or OT: garbage if he doesn't want to.
The poor SE has no choice.

My understanding of the PICLIST and its topics is this:

FIRST: The list is primarily for users of PICs.

SECOND: Its initial and still primary purpose for existing is to help people
get things done with PICs.

THIRD: It is an excellent resource for other non-PIC related engineering
info.

FOURTH: It can be, for some, a cool place to 'hang-out' and have need OT
(and now TECH) discussions.

What I am saying is there is no significant difference between and EE and an
SE in regard to the THIRD item above.

Say I am developing a PC-based application that has to do something with
CRCs that I don't understand. How is asking for help with that any different
from an EE asking a question about how to get packaging for a non-PIC
project?

I will repeat: Software types should NOT be second class citizens!

I personally follow TECH and would have no trouble dealing with issues
there, but what if the guy who is an expert on CRCs and could easily answer
my question doesn't care about GW, GE or black holes? (or whatever ends up
in TECH). Then I'm screwed.

Software people of the list, Unite!

---- Bob Ammerman

{Original Message removed}

2008\07\14@115945 by Bob Blick

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On Mon, 14 Jul 2008 09:55:20 -0400, "Bob Ammerman"
<.....rammermanKILLspamspam@spam@verizon.net> said:
> Okay,
>
> I agree this isn't EE

Hi Bob,

In my opinion, CRC belongs in EE because it is something an embedded
engineer will need to deal with.

The elephant in the room is the personalities involved in the original
post and the first reply.

Let's try to get over the personality issues.

Let's try to raise the quality of the posts.

Then everyone will be happy.

Cheerful regards,

Bob "I'm moderating, OK?" Blick

--
http://www.fastmail.fm - IMAP accessible web-mail

2008\07\14@120756 by Adam Field

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If you're router supports Openwrt (openwrt.org), they're an open
source project and you'll be able to see how the CRC is calculated. Or
you could first get openwrt running and use the command line tools
from there to reflash with your version.

There are some routers with JTAG headers. You can make cheap JTAG to
PC parallel port interfaces that you can flash/debug from.

I'm mostly talking about the Linksys WRT54G family, as they are very
hobbyist/homebrew friendly.

On Sun, Jul 13, 2008 at 3:02 PM, Tomás Ó hÉilidhe <toespamKILLspamlavabit.com> wrote:
>
> I'm trying to upload some custom firmware to my router but it won't
> accept the firmware file because the CRC check is wrong in it.
>
> What I did was I downloaded a legitimate ".bin" file from the router
> manufacturer and then edited it myself with a hex editor, but I don't
> know how to go about changing the CRC.
>
> Anyone know?
>
>

2008\07\14@122433 by Bob Ammerman

picon face
So, software that might be in an embedded app, or perhaps might communicate
with an embedded app is ok in EE?

But generic Linux/Windows stuff isn't.

Do I have it?

--- Bob

{Original Message removed}

2008\07\14@124905 by Bob Blick

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On Mon, 14 Jul 2008 12:23:57 -0400, "Bob Ammerman"
<.....rammermanKILLspamspam.....verizon.net> said:
> So, software that might be in an embedded app, or perhaps might
> communicate
> with an embedded app is ok in EE?
>
> But generic Linux/Windows stuff isn't.
>
> Do I have it?

Sounds good to me. We aren't making major changes to [EE], just
focusing.

Cheerful regards,

Bob

--
http://www.fastmail.fm - A no graphics, no pop-ups email service

2008\07\14@172150 by William \Chops\ Westfield

face picon face

On Jul 14, 2008, at 6:33 AM, sergio masci wrote:

>> You will have to find out what kind of "CRC" is used.  There is no
>> standard "CRC" algorithm.  There are literally thousands of CRC
>> methods in use.
>>
> The CRC algorithm is pretty standard (the only real variations  
> being start
> with all zeros, all ones, use 16 bit, 24 bit or 32 bit  
> accumulator), it's
> the polynomial that tends to vary.

I've seen the "image checksum" here vary from a simple checksum (unix  
"sum" command or IP checksum algorithm) to a CRC (with various  
polynomials), to an MD5 hash.  So yeah, the first step is figure out  
"what kind of CRC is used", keeping in mind that it might not be an  
actual CRC at all in the normal use of the term...

BillW

2008\07\14@190508 by Apptech

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I suggest that this discussion should be being held in TECH
as it relates to whether material belongs in TECH or
elsewhere. AND the subject line needs changing.

What say any responses are posted there? I'll
dual post this and with a changed subject line.


> My issue is this:

> An EE doesn't have to deal with TECH: or OT: garbage if he
> doesn't want to.
> The poor SE has no choice. ...


Having carefully read that, my original comment applies.

Core:

{Quote hidden}

I generally agree with your arguments. There may well be
many others who agree. It seems likely that such material
will be migrating out of EE (not my choice except as 1 of N
members). Letting the new arrangement settle down and then
seeing how people feel.

James argued for years that a proliferation of tags would
lead to administrative nightmares AND a demand for still
more tags. He may or may not prove right on the first point.
He seems to be being proven right on the second.



           Russell


2008\07\15@075344 by sergio masci

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On Mon, 14 Jul 2008, William "Chops" Westfield wrote:

{Quote hidden}

CRC is a specific term, just like sum, product and difference.

A CRC is a type of hash, so is a checksum and MD5 hash.

My mistake here was in assuming the CRC term was being used correctly :-)

Regards
Sergio Masci

2008\07\15@084028 by Apptech

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Bob - do you see this as EE ?
I'd say yes, but ... ?

{Quote hidden}

Yes, it can be used far too loosely.
But, as noted above, there are a large infinite number of
CRC algorithms and a significant number of common algorithms
that bear the name. At core CRC means "cyclic redundancy
check" and relates to the use of a shift register (actual or
notional) with feedback taps fed back from selected stages.
The stages chosen and length of register can (and do) vary
with application. Most possible arrangements are sub optimal
or just plain stupid :-).

All that said, CRC-16 is what is usually referred to and
relates to a specific arrangement. But, Y'All knew that ;-).

For a start on the potentially painful journey.

   http://en.wikipedia.org/wiki/Cyclic_redundancy_check

_________________________________

Painless intro, they say.
Also long

   http://www.geocities.com/SiliconValley/Pines/8659/crc.htm

_______________________________

Various embedded CRC-16 s

       http://www.digitalnemesis.com/info/codesamples/embeddedcrc16/

________________________________

Good page:

     CRC-16 0x8005 x16 + x15 + x2 + 1



     "123456789"
     1 byte checksum 221
     CRC-16 0xBB3D
     CRC-16 (Modbus) 0x4B37
     CRC-16 (Sick) 0x56A6
     CRC-CCITT (XModem) 0x31C3
     CRC-CCITT (0xFFFF) 0x29B1
     CRC-CCITT (0x1D0F) 0xE5CC
     CRC-CCITT (Kermit) 0x8921
     CRC-DNP 0x82EA
     CRC-32 0xCBF43926


   http://www.lammertbies.nl/comm/info/crc-calculation.html



2008\07\15@101207 by Bob Blick

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On Wed, 16 Jul 2008 00:37:28 +1200, "Apptech" <EraseMEapptechspam_OUTspamTakeThisOuTparadise.net.nz>
said:
> Bob - do you see this as EE ?
> I'd say yes, but ... ?

Yes Doctor, I concur(from the movie "Catch Me If You Can" riffing off
the TV series "Dr. Kildare").

Cheerful regards,

Bob

--
http://www.fastmail.fm - Or how I learned to stop worrying and
                         love email again

2008\07\15@112652 by Bob Ammerman

picon face

From: "Apptech" <apptechspamspam_OUTparadise.net.nz>
> Bob - do you see this as EE ?
> I'd say yes, but ... ?

If I'm the Bob you mean :-)

I'd say absolutely yes!
Even though the OPs original application may or may not have much to do with
embedded development. This is very useful information for embedded
developers.

-- Bob Ammerman
RAm Systems


{Quote hidden}

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