Updating GM EBCM Checksum

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Re: Updating GM EBCM Checksum

Postby Tazzi » Mon Feb 22, 2021 3:24 pm

RADustin wrote:The problem is, one a bad file is uploaded- the module goes into a 'soft brick' mode and if another bad file is tried it will brick.

I have never ever seen that occur. Calibrations will never brick a module.

If you are writing over the operating system also, then thats a different story.
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Re: Updating GM EBCM Checksum

Postby RADustin » Tue Feb 23, 2021 2:57 pm

Tazzi wrote:
RADustin wrote:The problem is, one a bad file is uploaded- the module goes into a 'soft brick' mode and if another bad file is tried it will brick.

I have never ever seen that occur. Calibrations will never brick a module.

If you are writing over the operating system also, then thats a different story.


My friend made me the hardware I’m flashing with... it basically emulates the MDI from what I understand and therefore flashes with the OS.

Currently I don’t have a way to cal only flash. Is your thought that if I could cal only flash, then it may work even with a bad checksum?

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Re: Updating GM EBCM Checksum

Postby Tazzi » Wed Feb 24, 2021 10:19 am

RADustin wrote:
Tazzi wrote:
RADustin wrote:The problem is, one a bad file is uploaded- the module goes into a 'soft brick' mode and if another bad file is tried it will brick.

I have never ever seen that occur. Calibrations will never brick a module.

If you are writing over the operating system also, then thats a different story.


My friend made me the hardware I’m flashing with... it basically emulates the MDI from what I understand and therefore flashes with the OS.

Currently I don’t have a way to cal only flash. Is your thought that if I could cal only flash, then it may work even with a bad checksum?


It will never work with a bad checksum. But doing a calibration only flash is MUCH faster.
Update the programming to do calibration only, and also to keep retrying to flash when its incorrect.
When it detects its incorrect, you can automated the software to simply increase the checksum byte by 1 and reflash. Eventually you will find the value.
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Re: Updating GM EBCM Checksum

Postby RADustin » Wed Feb 24, 2021 12:20 pm

Tazzi wrote:
It will never work with a bad checksum. But doing a calibration only flash is MUCH faster.
Update the programming to do calibration only, and also to keep retrying to flash when its incorrect.
When it detects its incorrect, you can automated the software to simply increase the checksum byte by 1 and reflash. Eventually you will find the value.


I'll work on implementing this. It's going to take me some time just to see how to set it up, I'll have to quiz my friend on the bootloader.

any idea of a non brute-force way to figure it? Seems like assembly(IDA) had promise, but I don't know much about it. Is there anything I can do to make an assembly strategy more effective?

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