GBDK Joypad Tutorial - Revision history

Bbbbbr: Oops, move joypad() read inside main loop. Also add wait_vbl_done() instead of using code-blocking delay()s. Fix a tile count bug

2021-06-24T06:06:06Z

Oops, move joypad() read inside main loop. Also add wait_vbl_done() instead of using code-blocking delay()s. Fix a tile count bug

Bbbbbr: Use better practices, only read call joypad() once per frame and operated on the cached result

2021-06-24T05:58:18Z

Use better practices, only read call joypad() once per frame and operated on the cached result

Caseyweederman: /* Tools */ Changed external links to internal ones

2016-06-24T12:51:35Z

‎Tools: Changed external links to internal ones

Gbjosh: /* Exercises */

2016-06-20T13:44:15Z

‎Exercises

Gbjosh at 14:47, 15 June 2016

2016-06-15T14:47:44Z

Gbjosh: /* The joypad() function */

2016-06-15T14:34:30Z

‎The joypad() function

Gbjosh: /* Tools */

2016-06-15T14:32:46Z

‎Tools

Gbjosh: /* The joypad() function */

2016-06-15T14:31:29Z

‎The joypad() function

Gbjosh: This tutorial aims to detail the use of the joypad with GBDK.

2016-06-15T14:21:59Z

This tutorial aims to detail the use of the joypad with GBDK.

New page

==Introduction==
This tutorial aims to detail the use of the joypad with GBDK.
==Tools==
You will need GBDK, and any knowledge of C.
==The joypad() function==
GBDK's gb.h features a joypad() function that returns the status of the joypad.

The joypad() function can return the status of the following inputs:

<pre>
J_START
J_SELECT
J_B
J_A
J_DOWN
J_UP
J_LEFT
J_RIGHT
</pre>

===Program 1: Return joypad() status===
Lets write a simple program to return the status of joypad() when a button is pressed:

<pre>
#include <stdio.h> // include this file for the printf() function
#include <gb/gb.h> // include this file for Game Boy functions

void main(void){

while(1) {

switch(joypad()) {

case J_RIGHT : // If joypad() is equal to RIGHT
printf("Right!\n");
delay(100);
break;
case J_LEFT : // If joypad() is equal to LEFT
printf("Left!\n");
delay(100);
break;
case J_UP : // If joypad() is equal to UP
printf("Up!\n");
delay(100);
break;
case J_DOWN : // If joypad() is equal to DOWN
printf("Down!\n");
delay(100);
break;
case J_START : // If joypad() is equal to START
printf("Start!\n");
delay(100);
break;
case J_SELECT : // If joypad() is equal to SELECT
printf("Select!\n");
delay(100);
break;
case J_A : // If joypad() is equal to A
printf("A!\n");
delay(100);
break;
case J_B : // If joypad() is equal to B
printf("B!\n");
delay(100);
break;
default :
break;
}
}
}
</pre>
===Program 2: Using waitpad() and waitpadup()===
There are also two more joypad functions that you can utilize:

<pre>
waitpad() // This function waits for a button to be pressed.
waitpadup() // This function waits for all buttons to be released.
</pre>

Lets use both the waitpad() function and the waitpadup() function in a simple program:

<pre>
#include <stdio.h> // include this file for the printf() function
#include <gb/gb.h> // include this file for Game Boy functions

void main(void){

while(1) {

printf("Please press A\n");
waitpad(J_A); // waitpad() is waiting for the A button to be pressed.
printf("You pressed A! Cool!\n\n");

printf("Hold down the LEFT button\n");
waitpad(J_LEFT); // waitpad() is waiting for the LEFT button to be pressed.
printf("You're holding down LEFT!\n");
waitpadup(); // waitpadup() is waiting for all buttons to be depressed but you have to hold down LEFT to get here so it is
// waiting on LEFT to be depressed.
printf("You've released LEFT\n\n\n");

}
}
</pre>
===Program 3: Moving a sprite on the display===
Now lets use the joypad() function to move a sprite on the screen. If you are inexperienced with GBDK sprites, you will need to view the [[GBDK Sprite Tutorial]].

<pre>
#include <gb/gb.h> // include this file for Game Boy functions

//Created with GBTD, exported to .c with options from: 0, to: 0, label: smile
unsigned char smile[] =
{
0x3C,0x3C,0x42,0x42,0x81,0x81,0xA5,0xA5,
0x81,0x81,0x81,0xA5,0x42,0x5A,0x3C,0x3C
};

void main(){

int x = 55; // Our beginning x coord
int y = 75; // Our beginning y coord

SPRITES_8x8;
set_sprite_data(0, 0, smile);
set_sprite_tile(0, 0);
move_sprite(0, x, y); // Move sprite to our predefined x and y coords

SHOW_SPRITES;

while(1){
if(joypad()==J_RIGHT) // If RIGHT is pressed
{
x++;
move_sprite(0,x,y); // move sprite 0 to x and y coords
delay(10);
}

if(joypad()==J_LEFT) // If LEFT is pressed
{
x--;
move_sprite(0,x,y); // move sprite 0 to x and y coords
delay(10);
}

if(joypad()==J_UP) // If UP is pressed
{
y--;
move_sprite(0,x,y); // move sprite 0 to x and y coords
delay(10);
}

if(joypad()==J_DOWN) // If DOWN is pressed
{
y++;
move_sprite(0,x,y); // move sprite 0 to x and y coords
delay(10);
}
}
</pre>

@@ Line 2: / Line 2: @@
 This tutorial aims to detail the use of the joypad with GBDK.
 ==Tools==
-You will need: [[GBDK]], a text editor, [http://www.devrs.com/gb/hmgd/gbtd.html GB Tile Designer], and an emulator ([http://bgb.bircd.org/ BGB] is recommended for its many debug features), and any level of knowledge of C.
+You will need: [[GBDK]], a text editor, [[Game Boy Tile Designer]], and an emulator ([[BGB]] is recommended for its many debug features), and any level of knowledge of C.
 Substitute your preferred tools if you want, but this tutorial is assuming you have those listed above.

← Older revision		Revision as of 13:44, 20 June 2016
Line 173:		Line 173:

	* Try changing the sprite when you press a key or switch directions.		* Try changing the sprite when you press a key or switch directions.
−	* Use J_START to "pause" or open a menu.	+	* Use J_START or J_SELECT to "pause" or open a menu.
		+	* Detect three buttons being pressed at once.[http://gbdev.gg8.se/forums/viewtopic.php?id=344]

← Older revision		Revision as of 14:47, 15 June 2016
Line 169:		Line 169:
	}		}
	</pre>		</pre>
		+
		+	==Exercises==
		+
		+	* Try changing the sprite when you press a key or switch directions.
		+	* Use J_START to "pause" or open a menu.

@@ Line 123: / Line 123: @@
 //Created with GBTD, exported to .c with options from: 0, to: 0, label: smile
-unsigned char smile[] =
+const unsigned char smile[] =
+{
 x3C,0x3C,0x42,0x42,0x81,0x81,0xA5,0xA5,
@@ Line 136: / Line 136: @@
 	SPRITES_8x8;
-	set_sprite_data(0, 0, smile);
 	set_sprite_tile(0, 0);
 	move_sprite(0, x, y); // Move sprite to our predefined x and y coords
@@ Line 142: / Line 143: @@
 	SHOW_SPRITES;
 	while(1){
 		if (joydata & J_RIGHT) // If RIGHT is pressed
+		{
 			x++;
 			move_sprite(0,x,y); // move sprite 0 to x and y coords
+		}
@@ Line 155: / Line 156: @@
 			x--;
 			move_sprite(0,x,y); // move sprite 0 to x and y coords
+		}
@@ Line 162: / Line 162: @@
 			y--;
 			move_sprite(0,x,y); // move sprite 0 to x and y coords
+		}
@@ Line 169: / Line 168: @@
 			y++;
 			move_sprite(0,x,y); // move sprite 0 to x and y coords
+		}
+	}
 </pre>

@@ Line 31: / Line 31: @@
 #include <stdio.h> // include this file for the printf() function
 #include <gb/gb.h> // include this file for Game Boy functions
 void main(void){
@@ Line 119: / Line 120: @@
 <pre>
 #include <gb/gb.h> // include this file for Game Boy functions
 //Created with GBTD, exported to .c with options from: 0, to: 0, label: smile
@@ Line 129: / Line 131: @@
 void main(){
-	int x = 55; // Our beginning x coord
+	uint8_t joydata;
-	int y = 75; // Our beginning y coord
+	uint8_t x = 55; // Our beginning x coord
 	SPRITES_8x8;
@@ Line 139: / Line 142: @@
 	SHOW_SPRITES;
 	while(1){
-		if(joypad()==J_RIGHT) // If RIGHT is pressed
+		if (joydata & J_RIGHT) // If RIGHT is pressed
+		{
 			x++;
@@ Line 147: / Line 151: @@
+		}
-		if(joypad()==J_LEFT)  // If LEFT is pressed
+		if (joydata & J_LEFT)  // If LEFT is pressed
+		{
 			x--;
@@ Line 154: / Line 158: @@
+		}
-		if(joypad()==J_UP)  // If UP is pressed
+		if (joydata & J_UP)  // If UP is pressed
+		{
 			y--;
@@ Line 161: / Line 165: @@
+		}
-		if(joypad()==J_DOWN)  // If DOWN is pressed
+		if (joydata & J_DOWN)  // If DOWN is pressed
+		{
 			y++;

@@ Line 7: / Line 7: @@
 ==The joypad() function==
-GBDK's gb.h features a joypad() function that returns the status of the joypad.
+GBDK's [[gb.h]] features a joypad() function that returns the status of the joypad.
 The joypad() function can return the status of the following inputs:

@@ Line 20: / Line 20: @@
 ===Program 1: Return joypad() status===
 Lets write a simple program to return the status of joypad() when a button is pressed:
@@ Line 71: / Line 74: @@
 </pre>
 ===Program 2: Using waitpad() and waitpadup()===
 There are also two more joypad functions that you can utilize:
@@ Line 103: / Line 109: @@
 </pre>
 ===Program 3: Moving a sprite on the display===
 Now lets use the joypad() function to move a sprite on the screen. If you are inexperienced with GBDK sprites, you will need to view the [[GBDK Sprite Tutorial]].