Author Topic: I just got done reading! (Read 4857 times)

juha.kivekas · « **on:** March 31, 2013, 12:28:32 pm »

I just got done reading the TI-83plus assembly guide for absolute begginners, so im currently working on something thats propably way too hard and ambitious for me. I think im going to flip this place around for all the info i need to make my very first puzzleish game. i've done it before in other languages so that should help me a little.
Im going to share something from my past projects that quite perfectly merged with calculator programming due to the forced lo-fi graphics. Last summer i implemented some dithering algorithms on BMP files in java. I altered the program so it printed the file as ASM source code, so that i could then wiev them on my calc.
About Dithering: http://en.wikipedia.org/wiki/Dithering#Digital_photography_and_image_processing
Original BMP image:

The picture drawn on my TI-84+, and me in my fur hat:

Juha Kivekas, from frozen finland

Xeda112358 · « **Reply #1 on:** March 31, 2013, 12:32:58 pm »

Wow, that looks pretty nice o.o I have very little knowledge in dithering stuff, but you will definitely find people here with assembly knowledge! So, what are you working on?

Also, welcome to Omni, here are some

juha.kivekas · « **Reply #2 on:** March 31, 2013, 12:45:36 pm »

Well im working on emtying the plotsscreen first, because my picture keeps staying in the background when other programs draw sprites. The sprites thenagain are to be panels of my lights out puzzle game. Lights out is a classic handheld game. Here its made as a SVG with embedded javascript:
www.guttula.com/LightsOut.svg
Might not work, so wikipedia:
http://en.wikipedia.org/wiki/Lights_Out_(game)

Xeda112358 · « **Reply #3 on:** March 31, 2013, 01:26:21 pm »

hmm, one way to clear plotSScreen uses the fact that it is 768 bytes, so you can do:

Code: [Select]

     ld hl,plotSScreen
     ld bc,768
Loop:
       ld (hl),0
       inc hl
       dec bc
;test if bc=0
       ld a,b
       or c
       jr nz,Loop
     ret

That is a routine that has a lot of optimising that can be done to it, but it might be easier to follow than some of the following.

Spoiler For Spoiler:

Code: [Select]

;alter the above code, saving 2300 t-states
     ld hl,plotSScreen
     ld bc,300h    ;300h = 768. So C=0, B=3
     ld a,c
Loop:
       ld (hl),a     ;1 byte, 7 cycles, compared to 'ld (hl),0' which is 2 bytes, 10 cycles
       inc hl
       dec bc
;test if bc=0
       ld a,b
       or c
       jr nz,Loop
     ret

Code: [Select]

;alter the above code to replace everything after 'inc hl'
;saves 7675 t-states, so 9975 t-states saved in all so far. Also a few bytes smaller.
     ld hl,plotSScreen
     ld bc,300h    ;300h = 768. So C=0, B=3
     ld a,c
Loop:
     ld (hl),a
     cpi            ;not using it for its inteaded use. Still, increments HL, decrements BC, checks if BC is 0
     jp pe,Loop
     ret
;25378 t-states, 14 bytes

Here is a different approach:

Code: [Select]

     ld hl,plotSScreen
     ld bc,3    ;768 = 300h, but here we load 3 into C, 0 in B
     sub a      ;set A=0, more optimised than 'ld a,0'
Loop:
       ld (hl),a
       inc hl
       djnz Loop
       dec c
       jr nz,Loop
     ret
;15 bytes, 19789 t-states

And probably the best method for speed and size:

Spoiler For Spoiler:

Code: [Select]

     ld hl,plotSScreen
     ld (hl),0
     ld de,plotSScreen+1
     ld bc,767
     ldir
     ret
;13 bytes, 16152 t-states

juha.kivekas · « **Reply #4 on:** March 31, 2013, 01:54:37 pm »

First i was looking for a function to B_CALL but decided to build my own. Well, i made up something quite close to the ones you suggested:

Code: [Select]

EmptyBuffer:
	LD BC,768
	LD A,0
	LD HL, plotsscreen
BufferLoop:
	LD (HL),A
	INC HL
	DEC BC
	CP C
	JR NZ, BufferLoop
	CP B
	JR NZ, BufferLoop
	B_CALL _GrBufCpy
	ret

Thanks!

Xeda112358 · « **Reply #5 on:** March 31, 2013, 02:11:05 pm »

Aha, nice! The way you used A for two purposes is clever. You can also use 'xor a' or 'sub a' as a clever way of setting A=0. It saves a byte, among other things.

Stefan Bauwens · « **Reply #6 on:** March 31, 2013, 02:16:32 pm »

Hi there. Welcome here.

I'm not "acquainted" with dithering-stuff.(I mean, I know what it is, but I don't know much of the logic behind it).

I wish you luck with all your programs. I personally am not (yet?) an assembly coder, but I'm sure you'll find enough here that do.

DJ Omnimaga · « **Reply #7 on:** March 31, 2013, 06:23:27 pm »

Heya and welcome here

. Nice to see a new assembly programmer around

Sorunome · « **Reply #8 on:** March 31, 2013, 09:24:28 pm »

Welcome to omnimaga!
Have fun ~~losing the game~~ with your stay!

chickendude · « **Reply #9 on:** March 31, 2013, 11:41:19 pm »

What about:

Code: [Select]

clearGbuf:
	ld b,64			;7t - clear 64 rows
	ld (saveSP),sp		;20t - save the SP with SMC
	ld hl,0			;10t - we're going to push hl, so it will push two 0's wherever the stack is pointing (the gbuf)
	ld sp,plotSScreen+767	:10t - remember, the stack works backwards, so start at the end of gbuf
clearLoop:
	push hl			;11t - 2 each push clears 2 bytes
	push hl			;11t - 4
	push hl			;11t - 6
	push hl			;11t - 8
	push hl			;11t - 10
	push hl			;11t - 12 erase one row
	djnz clearLoop		;13/8t - repeat 63 times
saveSP = $+1
	ld sp,$0000		;10t - restore sp (the $0000 will get overwritten with SMC)
	ret

...just over 5000 t-states

The bcall btw is _GrBufClr.

EDIT: But the most common method is by far the ldir one. The bcall is fine, too, but if you need a bit more speed the ldir routine is pretty small and much quicker than the bcall.

Xeda112358 · « **Reply #10 on:** April 01, 2013, 06:15:05 am »

That is always an awesome way to do it

TIfanx1999 · « **Reply #11 on:** April 01, 2013, 09:32:03 pm »

Welcome to Omnimaga juha.kivekas. Nice use of dithering there. ^^

Author Topic: I just got done reading! (Read 4857 times)

juha.kivekas

I just got done reading!

Xeda112358

Re: I just got done reading!

juha.kivekas

Re: I just got done reading!

Xeda112358

Re: I just got done reading!

juha.kivekas

Re: I just got done reading!

Xeda112358

Re: I just got done reading!

Stefan Bauwens

Re: I just got done reading!

DJ Omnimaga

Re: I just got done reading!

Sorunome

Re: I just got done reading!

chickendude

Re: I just got done reading!

Xeda112358

Re: I just got done reading!

TIfanx1999

Re: I just got done reading!