Get the button press!

Right, so if you're using ASM and you want to check button presses, you move $FFFFF603 or $FFFFF605 to d0. (In Sonic 1 that is) That's about all I really get at this point.


What I do know is one of those checks for pressed buttons and one checks for held buttons. IIRC, to check for pressed buttons you have to use hex values, and you have to use decimal for the other.


The thing is, I'm completely lost as to what values is that button. I just know that B is both $10 and #4, and I'm not really sure about the others.


So I would like to know the both the decimal and hex values for each of the buttons. Whether you up and post it, or post a link is fine by me.

 

I think you're pretty confused. In Sonic 2, $F602 is used for buttons being held and $F603 is used for buttons being pressed newly this frame. Both these variables are bitfields, with each bit representing one button:

Code:

7 6 5 4 3 2 1 0

S A C B R L D U

Now there are two main ways to find out the value of a particular button - ANDing or BTSTing. A btst does what the name suggests - it tests a bit and sets the Z flag if it's equal to 0. In a btst, you supply the bit location of the button, so if for example you wanted to check if B was being held, you could do

Code:

btst #4, ($FFFFF602).w

bne.s SomeRoutineWhenBIsHeld

(you could transfer it to a register if you want, but it's not necessary)



ANDing, on the other hand, does a bitwise AND operation, and actually modifies the variable being ANDed, so it's generally used with data registers. For an AND, you need to supply the actual value for the button. As an example, if C was being pressed, $F603 would look like 00100000. In hex, this is $20, so you'd do something like:

Code:

move.b ($FFFFF603).w, d0

and.b #$20, d0

bne.s SomeRoutineWhenCIsPressed

The values for each button are:

Code:

$80 - Start

$40 - A

$20 - C

$10 - B

$08 - R

$04 - L

$02 - D

$01 - U

You can add values together for multiple buttons. Basically, if you're using an AND, you use these, if you're using a btst you just use the bit position of the button:

Code:

7 - Start

6 - A

5 - C

4 - B

3 - R

2 - L

1 - D

0 - U

This is for Sonic 2, but I'm pretty sure it's the same in Sonic 1.

 

Thanks a ton. I guess it shows I got lost by the wayside there.

 

I never knew the difference between btst and and. Thanks for sharing that.

 

B) Shobiz B) May I have your Permition to use this in a tutorial i want to write one based on Adding Custom Attacks Like Peel out Dash But On ButtonPress. I want to make this tutorial as detailed as possible.


Just need your Reply.

 

Sure, no problem.

 

sorry for huge bump but someone has to say it: this topic is worth to be pinned or something!