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Offline critor

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Downgrade your Nspire CX
« on: March 27, 2012, 04:51:46 am »
Since OS 3.0.2.1791, minimal installable OS version was set to 3.0.2.1785. This number is written in NAND outside the filesystem, and is not cleaned by any official menu.

It was impossible for your Nspire to go back to OS 3.0.1.1753 for example.

But some of us wanted to keep the possibility to go back to that OS.

Indeed, OS 3.0.1 had:
  • some flaws fixed on newer versions
  • the possibility to open partialy encrypted Lua scripts
  • a working Lua print() function which let you control external peripherals thanks to the RS232 port of the dock connector
Today thanks to Bsl and TI-Planet, you've got the choice with our new Ndless program: downgradeCX! ;D




Like Nleash and downgradeFix, downgradeCX just erases the NAND page containing the minimal installable OS version.

But it's also better in the following ways:
  • Unlike Nleash, downgradeCX doesn't remove the OS. You can go on using the OS untill you decide to downgrade, or even change your mind and in the end not downgrade at all. ;D
  • Unlike downgradeFix, downgradeCX doesn't need the OS to be removed or a specific Boot2 version to be flashed - which required an external USB/TTL2 interface! ;D
Note that the downgrade protection is only temporarily removed. If the calculator does reboot before you downgrade, you'll have to run downgradeCX again.

Also, downgradeCX needs Ndless 3.1. It won't be able to save you if you upgrade to OS 3.2 which will block Ndless. But the downgrade source code now publicly exists, and you'll just need to inject it with a flaw, if such a flaw still exists in the next OS...





Download from the TI-Planet news:
http://tiplanet.org/forum/viewtopic.php?p=122163#p122163
« Last Edit: March 27, 2012, 04:55:49 am by critor »
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Offline Lionel Debroux

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Re: Downgrade your Nspire CX
« Reply #1 on: March 27, 2012, 05:04:53 am »
That the downgrade of CX models is now possible, is obviously a great news :)
« Last Edit: March 27, 2012, 05:06:17 am by Lionel Debroux »
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Offline Jonius7

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Re: Downgrade your Nspire CX
« Reply #2 on: March 27, 2012, 05:05:57 am »
It does look very nice overall! Shall benefit the community greatly, and bring some relief to the feeling of being stuck on 3.0.2.
;)
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Offline DJ Omnimaga

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Re: Downgrade your Nspire CX
« Reply #3 on: March 27, 2012, 02:23:41 pm »
Nice to see those OSes are finally downgradeable without extra hardware. I wonder if this will work with OS 3.2... :)
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Offline Lionel Debroux

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Re: Downgrade your Nspire CX
« Reply #4 on: March 27, 2012, 02:44:21 pm »
Quote
I wonder if this will work with OS 3.2... :)
Probably, when there is arbitrary code execution for that OS family.
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Offline Chockosta

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Re: Downgrade your Nspire CX
« Reply #5 on: March 27, 2012, 02:45:09 pm »
That's awesome news :)
Is there a version for non-CX or do we have to use downgradefix ?
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Offline critor

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Re: Downgrade your Nspire CX
« Reply #6 on: March 27, 2012, 03:02:06 pm »
Quote from: Chockosta on March 27, 2012, 02:45:09 pm
Is there a version for non-CX or do we have to use downgradefix ?

It has not been adapted for non-CX yet, meaning that you still have to stick with downgradeFix + Boot2 1.4 (to flash through RS232 - as no FlashBoot2 has been released for Ndless 3.1 either).
« Last Edit: March 27, 2012, 03:02:29 pm by critor »
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Offline apcalc

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Re: Downgrade your Nspire CX
« Reply #7 on: March 27, 2012, 04:18:07 pm »
Yes!  Great news!  Wonderful to see such an accomplishment! :)
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Offline cyanophycean314

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Re: Downgrade your Nspire CX
« Reply #8 on: March 27, 2012, 10:23:37 pm »
Great achievement! Although, I don't really need it...  :-\
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Offline TheNlightenedOne

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Re: Downgrade your Nspire CX
« Reply #9 on: May 19, 2012, 10:17:44 pm »
This is pretty cool... I wonder what can be done with the Lua print() function.
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Offline Jim Bauwens

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Re: Downgrade your Nspire CX
« Reply #10 on: May 20, 2012, 05:23:36 am »
The lua print function will be returning in the future (probably OS 3.3).
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Offline Lionel Debroux

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Re: Downgrade your Nspire CX
« Reply #11 on: May 20, 2012, 05:29:43 am »
Quote
I wonder what can be done with the Lua print() function.
The Lua print() function makes it possible to output bytes to the RS232 port, and thereby control external devices. 0x00 cannot be emitted, but all other bytes can be emitted :)

On OS 3.1.0.392, Ndless can, as an example of modifying or expanding the functionality of the OS, restore the Lua print() functionality removed by TI. See the fixprint team work: http://ourl.ca/15649 / http://ti-pla.net/t8931 / http://ti-pla.net/a4227 :)
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