Hello everybody. I'm new to the forum so this is my first post.
Last night I updated my SDS1102CML to Lecroy firmware and noticed that the same logo appeared during boot.
Things to work with: - Someone pointed out that the CFG file contains the Boot image
Hints: Opening the CFG file you can see the name Siglent in a few places (Eg: se–golonhceT tne“giS.SDS -AKA: SDS Sig"ent Technolog-es)
So onto the reverse engineering...
If you alter the file it will give you a integrity error.
- First test : increase one byte by 1 and decrease the next by 1. - Passed file integrity so it's a Checksum
- Look for the Image in the file - It's 480x234 - begins at offset 0xD8 ends at 0x52518 and is a 24bit bitmap - 3 bytes per pixel
- Replaced the image with a same sized picture:
-Make checksum equal to 8 bit total - not working
-16 bit checksum - still not working
-24 bit working
(For reference try keeping the checksum of the image 0xC703A1)
Then compared the CML and CNL versions, they have the same image logo with a few differences:
-CNL @ 0x94 has a 0, CML has a 1 (CML has +1)
-CNL @ 0xD7 has a C6, CML has a C5 (CML has - 1)
-That means that until 0x52518 (where the image ends) checksum shoud be identical for both scopes
-After the end of the image there are two bytes that are in fact reverse order checksum -
CML - 96 8D
CNL - 9B F8
-Difference between these is the same as the difference between the two footers (IN REVERSE 0x056B) so it seems like it's trying to maintain a constant total checksum. (maybe keeps a total Chksum of 3C88700)
Conclusion:
- You can change the image if you maintain the Checksum without any risk of damage
- Also change the name of the device - same condition applies
If you have any suggestions / ideas for future or your own research please feel free to post.
Will post images of modified splash screen this evening.
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