Great! Take your time... I myself am burdened with assignments. No hw for AP Calc though!

I hate Christmas assignments. When I went to college we practically had no Christmas break. X.x

Nice work Apcalc by the way.

Here are the syscalls_[ncas/cas]-2.1.c

The bug is still there ...
I have double check hard coded and syscalls-lights adresses.

The only supposed issues are :
 - the changed subroutine make Ndless bug
 - one error in syscalls_[ncas/cas]-2.1.c

For those how know better the Nspire than me, here is the backtrace from the nspire-emu when I want to install Ndless 2.1 on an emulated 2.1 CAS :

Error at PC=0000032C: Cannot shift memory offset by register
        Backtrace:
Frame     PrvFrame Self     Return   Start
1800E06C: 1800E0DC 1800E070 102086F0 1020BC24
1800E0DC: 1800E14C 1800E0E0 101FF880 102071C4
1800E14C: 1800E194 1800E150 101FF294 101FF7E0
1800E194: 1800E8B4 1800E198 10041A1C 101FF1F4
1800E8B4: 1800E93C 1800E8B8 1002B32C 100419C8
1800E93C: 1800EA6C 1800E940 1000A684 1002B2E8
1800EA6C: 1800ECB4 1800EA70 101D5684 1000A620
1800ECB4: 1800ECF4 1800ECB8 101D3F00 101D51C0
1800ECF4: 1800FA54 1800ECF8 1000E1F0 101D3D48
1800FA54: 1800FAA4 1800FA58 1000EAA8 1000E180
1800FAA4: 1800FABC 1800FAA8 1025B22C 1000E8F0
1800FABC: 1800FB0C 1800FAC0 101C701C 1025B164
1800FB0C: 1800FCB4 1800FB10 101C7364 101C6EEC
1800FCB4: 1800FCD4 1800FCB8 101C73EC 101C723C
1800FCD4: 1800FD34 1800FCD8 1000F16C 101C73BC
1800FD34: 1800FD9C 1800FD38 100012A4 1000EF5C
1800FD9C: 1800FDD4 1800FDA0 102F2640 10000FE8
1800FDD4: 1800FDF4 1800FDD8 10279F40 102F25F4
1800FDF4: 1800FDF8 1800FDF8 00000000 10279F28
debug>

EDIT :
I noticed, that randomly, i had some pixels on the top of the screen :

My mistake, these instructions cannot be used in Thumb state.

Yet another bug fix:

• Garbage on screen after program execution:
  The documents screen is not refreshed as it was on OS 1.7. Sometimes the screen is even shifted to the left.
  Workaround: turn the calculator off and on.
  

For the shifted screen, my tests tell me that:
- It is only caused by read then write from and to the screen buffer (for example the fading loop at the beginning of the particles demo)
- Once shifted, it remains as it is in the program and the OS
- The problem will only appear at certain read/write frequencies (shortening the delay it the fading loop of the demo solves the problem)

I don't really understand how it disturbs the LCD controller, but I recommend not to use byte-size read+write operations on the screen buffer - use instead a copy of the whole screen to read from.

Levak: the skip offset in s2_tizip_hook has changed, maybe this is why it crashes on your side.
I have commited a version that installs on OS 2.1.0 but crashes in ndless_tests, there's probably a wrong address for one of the syscalls.

All the tests now pass on OS 2.1.0 CAS and non-CAS.
The particles demo works on my own Clickpad.
Thanks to Levak for providing some of the addresses.

show_dialog_box2() requires on OS 2.1.0 the interrupts to be enabled else the keyboard won't work. I will provide a wrapper function to make this transparent. Until then some programs such as Block Dude will hang when showing popups.

shrear, that's strange. Could you please try this update which brings full support, at least on nspire_emu?

Goplat: I think I will change clear_cache() with your suggestions that make sense, if it is still stable on real hardware.

Now I feel there are still two main features to be added before moving to the beta-testing phase:

• Compatibility with the Touchpad arrows: According to Goplat the hardware interface is not simple, I'm not sure how to add this. Should a function that implement the protocol be added to libndls? Could it have the same signature as isKeyPressed() for the migration of existing program to be transparent? Or should we move instead to OS functions, if they exist?
• A simple console: it would integrate with programs through stdin and stdout/stderr (replacing the default RS232 interface), to make ports of non-TI-Nspire programs easier. There would be a prompt, the keyboard would be used to type in strings, echo-ed on the screen. stdout/stderr would be displayed on the scrolling screen.
  I may also create a simple shell with history and auto-completion of file names to make possible the execution of command-line tools with arguments.

• Compatibility with the Touchpad arrows: According to Goplat the hardware interface is not simple, I'm not sure how to add this. Should a function that implement the protocol be added to libndls? Could it have the same signature as isKeyPressed() for the migration of existing program to be transparent? Or should we move instead to OS functions, if they exist?
• A simple console: it would integrate with programs through stdin and stdout/stderr (replacing the default RS232 interface), to make ports of non-TI-Nspire programs easier. There would be a prompt, the keyboard would be used to type in strings, echo-ed on the screen. stdout/stderr would be displayed on the scrolling screen.
  I may also create a simple shell with history and auto-completion of file names to make possible the execution of command-line tools with arguments.

I say that the OS functions should not be used, as they certainly do not exist for OS versions less than 2.0. libndls functions to interface with the touchpad might be a good idea. Also, that console idea sounds terrific.