Is there any harm in sending the OS from this "source" without the boot2 code. I sent 1.1 and it worked fine. Is this normal, or do I have to add the boot2. Also, if TI ever released a OS that was not downgradeable, would it be possible to put an old boot2 code in the file and send it so it is possible to downgrade? Thanks!
You can send all OSes without the boot2, by removing it from the tnc/tno archive if necessary. The OS will work, because you allready have a boot2 in your TI-Nspire! Without the boot2, the USB plug wouldn't work anyway, and you wouldn't be able to send anything...
But no, it is not possible to downgrade the boot2 from 1.4 to 1.1, by just putting the old boot2.file with a matching boot2.cer file in a tnc/tno archive.
I've allready tried, and managed to get a correct tnc/tno file, but the boot2 was not updated. Looking at the debug log, I've figured out what happens:
The newly installed OS first boots with the calculator boot2. After booting, the OS checks the boot2 version, and updates it if there is a newer version in the tnc/tno archive.
So if you've got a TI-Nspire with boot2 1.1 and send a tnc/tno with boot2 1.4, the boot2 will be updated after the 1st boot of the OS.
If you've got a TI-Nspire with boot2 1.4 and send a tnc/tno with boot2 1.1, the boot2 won't be updated, because it is not a newer version.
We could surely write the old boot2 1.1 using Ndless and a specific program which could be named "boot2writer".
But, this is dangerous: If the programs fails for any reason and leaves you with an invalid boot2, your TI-Nspire won't boot any more... And you won't be able to install a new OS/boot2, because the USB plug won't work any more...
By the way, I've found a boot2 related bug with OS 2.1.
On a TI-Nspire basic with the old boot2 1.1 and OS 2.1, the calculator just freezes when the "loading OS" progress bar reache 100%. Notice in that case, your boot2 won't be updated beacause the OS hasn't started yet. So a reboot will fail too!
There is no problem with boot2 1.4. Strangely, there is no problem either on a TI-Nspire CAS with boot2 1.1.