CRC - Encoder for NEC 3540 Fimware

I read that this information are in the forum but I can’t find it :frowning:

So I need to Know how works the CRC Encoder to calculate de Checksum of the Nec 3540 Firmware.

I have some experience with the CRC and I know that it can have the polly you want and even theres diferentes algos for calculate de Checksum. You Can creat your own CRC Encoder.

What I want is to play with the firmware, for start I want to play with the “VIDEO_TS” string :slight_smile:

Some info Please :bow:

Nobody knows anything?

I appreciate an answer, please!

CRC algorithm isn’t used for calculating the checksum for Nec firmwares but a much simpler WORD summing.

Thanks for the answer, but how this thing of “WORD summing” works?
Please :wink:

I think that I understand how it works, I will try with a known firmware (because it already has the checksum and I only need to compare) :slight_smile:

You just sum all (unsigned) 16-bit values of the firmware… if you need the method written in C++ just drop me a PM.

I think everyone who is unable to write such a program himself should keep his fingers away from patching firmwares.

He, He!

I have to say that I already made a program to calculate the checksum, and of course it works :wink:

Like Quikee said it’s just a “simpler WORD summing”.

So Liggy can I patch firmwares? :bigsmile:

Hehe… this was the easiest part of patching. It’s just 5 lines of code for recalculating the checksum. =P

I agree :iagree: , I have to say that I don’t know nothing about the NEC firmware :sad: , I just know how to remove the RipLok, that is the easiest thing that even a child can do :smiley:

Maybe someone can send me some links with some info about the NEC 3540 firmware :rolleyes:

There are no detailled links about the 3540 firmware. You could try to analyze structures in the firmware. It’s not difficult to find the MIDs for example.