I tried to make an offscrpt that saves your ram on poweroff:


Code:


But it just crashes my calculator when I turn it off. Ideas?
PS I did set 1, (iy+34h)

I never understood how do OFFSCRPTs work, can you tell me more about them ?

Matrefey: You can read more about OFFSCRPTs here: http://wikiti.brandonw.net/index.php?title=Offscrpt
Parrot: "and set bit 1 of (iy+33h) to indicate that an OFFSCRPT appvar is installed." I'm not sure what 1,(iy+34h) is.

Well...

- Before calling OFFSCRPT, the OS turns the LCD off and disables all interrupts (via port 3.)
- GroupAllVars tries to push something on the FPS, but because the homescreen edit buffer is open, there is no free RAM, so PushRealO1 throws an error.
- The system error handler is invoked; as you would expect, it displays the "ERR:MEMORY" screen (you can't see that it has done so because the LCD is turned off.) It then jumps to Mon, which calls GetKey.
- GetKey halts the CPU, which freezes the system since interrupts have been disabled.

There are a few lessons to be learned from this:
- You can't do something that involves creating or deleting variables while an edit buffer is open.
- OFFSCRPT is not set up to handle system errors at all. If you are thinking of calling a system routine that has any possibility whatsoever of throwing an error, you must set an error handler first.
- When OFFSCRPT is called, the calculator hardware is not in what you could call a sane state (port 3 set to 8). (edit: that's eight-paren, not .)

I think the fundamental problem here, though, is that trying to do anything complicated while the calculator is turning off is a bad idea. (The same would be true if you used an app-change hook or homescreen hook instead of OFFSCRPT.) GroupAllVars, for instance, would cause you problems even if it were working "properly": what would you expect it to do when it needs to garbage-collect? A better idea would be to use OFFSCRPT to set up a hook (or other mechanism) that will do the work of grouping variables after the calc turns back on.

As I was telling parrotgeek on SAX, what Doors CS does (and thanks to BrandonW for this idea) is to use an OFFSCRPT to set up a GetKeyHook. When the calculator turns back on, regardless of what turned it off, the GetKeyHook will fire when the calculator first checks for a key. The GetKeyHook cancels itself, then does whatever needs to be done (for example, launching Doors CS). I think that's probably a decent sort of standard design for many tasks to be performed on power-on.

Seems like a sane choice from a programming point of view, but not so much usability wise, if you expect this program to group all of your programs and protect them from a RAM reset if the battery is pulled while it is off.

True. Well, what I would probably do, if I wanted to write such a utility, is to create the group completely by hand (potentially including garbage collection, if need be.) And check to see whether the group already exists and whether any variables have been changed. But that would be considerably more difficult.

Code:


so it does make the group, but the screen does not turn on while doing so.
also, when turning back on and hit continue or do not show again, calc crashes. how to fix?
do I need to reopen edit buffer? how?
and what is port 3 normally set to when calc is off?