Rockbox Development > New Ports

SanDisk Sansa c200v2, m200v4, clipv1, clipv2, clip+, and fuzev2

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Bagder:
Ah, cool. So perhaps the test (by rondestvedt 2008-01-05) that didn't manage to "upgrade" to a modified firmware altered strings in a section that did't get the checksum properly updated!

rondestvedt:
My first test was flawed. I thought the checksum was just a simple addition of all chars in the file. After looking at Badger's code for the  checksum and seeing that it was adding 32bit integers instead of 8bit chars like I thought, I tried again, but instead of switching two letters side by side, I switched a group of 4 characters that were 32bit aligned with the beginning of the file. This time it successfully upgraded with the modified firmware, and I was able to see the changes I made. However this was just a simple switch, and the original checksum was not modified. I'm still wondering if the last 32 bits of the file is another checksum, as they differ between the versions 11 and 14.

Bagder:
Then I guess another test would be to actually test with a changed checksum. And also see if you can change the file in another "section" than the first.

hth:

--- Quote ---UTF16 little endian to be specific, and I don't understand why that would tell if the image is complete or not...
--- End quote ---
This alone definetly doesn't tell that, sorry.

I was referring to my previous post: When first examining the firmware i didn't find an error message i was looking for and thought that maybe the e200p*.bin didn't contain the entire firmware, which seems to be wrong.

There's still a slight chance left for some hidden bootloader code on the flash.

I'm not sure yet either, but perhaps the firmware is a modification of AMS 's SDK for the AS352xs, which seems to be possibly build upon Segger's embOS, embFile and embWin. It also looks like the firmware contains parts of libjpeg for decoding jpeg files.

Sorry again if somebody got the idea that you can tell wether a complete
firmware image is distributed by a vendor by just looking at the encoding of
strings.

rondestvedt:
I tried the same method, and it did not work. I did notice in the firmware files some strings that seem to be a diagnostic menu, with references to various kinds of tests, such as a sdram test and other hardware tests. Not sure but this testing mode might be related to a recovery mode, if we could find out how to activate it.

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