Is there a way to remove "getKey"'s input lag?

Question

I've recently decided to try ti-basic programming, and while I was playing with getKey; I noticed that it had a 1s~ input lag after the first input. Is this built into the calculator, or can this be changed?

Answer 1

I figured out this myself too when I was experimenting with my Ti-84 during the summer. This lag cannot be changed. This is built into the calculator. I think this is because of how the microchip used in ti-84 is a Intel Zilog Z80 microprocessor which was made in 1984.

Answer 2

This is unfortunately simply the inefficiency of the calculator. TI-basic is a fairly high-level language and meant to be easy to use and is thus not very efficient or fast. Especially with respect to input and output, i.e. printing messages and getting input.

Answer 3

I recognize that "Quick Key" code above ;) (I'm the original author and very glad to see it spread around!).

Anyway, here is my low-level knowledge of the subject:

The operating system uses what is known as an interrupt in order to handle reading the keyboard, link port, USB port, and the run indicator among other things. The interrupt is just software code, nothing hardware implemented. So it is hardwired into the OS not the calculator.

The gist of the code TI uses is that once it reads that a key press occurred, it resets a counter to 50 and decrements it so long as the user holds down the key. Once the counter reaches zero, it tells getKey to recognize it as a new keypress and then it resets the counter to 10. This cause the initial delay to be longer than subsequent delays.

The TI-OS allows third party "hooks" to jump in and modify the getkey process and I used such a hook in another more complicated program (Speedy Keys). However, this hook is never called during BASIC program execution except at a Pause or Menu( command, where it isn't too helpful.

Instead what we can do is setup a parser hook that modifies the getkey counters. Alternatively, you can use the QuickKey code above, or you can use Hybrid BASIC which requires you to download a third-party App. A few of these apps (BatLib [by me], Celtic 3, DoorsCS7, and xLIB) offer a very fast getKey alternative as well as many other powerful functions.

The following is the code for setting up the parser hook. It works very well in my tests! See notes below:

#include    "ti83plus.inc"  ; ~~This column is the stuff for manually
_EnableParserHook = 5026h   ;   creating the code on calc. ~~
.db         $BB,$6D         ;AsmPrgm
.org $9D95                  ;
    ld hl,hookcode          ;21A89D
    ld de,appbackupscreen   ;117298
    ld bc,hookend-hookcode  ;010A00
    ldir                    ;EDB0
    ld hl,appbackupscreen   ;217298
    ld a,l                  ;7D
    bcall(_EnableParserHook);EF2650
    ret                     ;C9
hookcode:                   ;
    .db 83h                 ;83
    push af                 ;F5
    ld a,1                  ;3E01
    ld (8442h),a            ;324284
    pop af                  ;F1
    cp a                    ;BF
    ret                     ;C9
hookend:                    ;

Notes: other apps or programs may use parser hooks. Using this program will disable those hooks and you will need to reinstall them. This is pretty easy.

Finally, if you manually putting this on your calculator, use the right column code. Here is an animated .gif showing how to make such a program:

You will need to run the program once either on the homescreen or at the start of your main program. After this, all getKeys will have no delay.

Answer 4

Quick Key

:AsmPrgm3A3F84EF8C47EFBF4AC9

This is a getKey routine that makes all keys repeat, not just arrows and there is no delay between repeats. The key codes are different, so you might need to experiment.