Controller Input

Reads the SNES controller and displays which button is currently held. The simplest possible input example — press a button, see its name on screen.

Screenshot

What You'll Learn

• How to read controller state with padHeld(0) (returns a 16-bit bitmask)
• The SNES button constants: KEY_A, KEY_B, KEY_X, KEY_Y, KEY_L, KEY_R, KEY_UP, KEY_DOWN, KEY_LEFT, KEY_RIGHT, KEY_START, KEY_SELECT
• That the NMI handler reads joypads automatically — no manual polling needed
• The difference between padHeld() (held right now) and padPressed() (just pressed this frame)

Controls

Button	Display
A	"A PRESSED"
B	"B PRESSED"
X / Y	"X PRESSED" / "Y PRESSED"
L / R	"L PRESSED" / "R PRESSED"
D-pad	"UP/DOWN/LEFT/RIGHT PRESSED"
START / SELECT	"START/SELECT PRESSED"
None	(blank)

SNES Concepts

How Input Works on the SNES

The SNES joypad is a shift register — the hardware clocks out 16 bits of button state every frame during the auto-joypad read period (after VBlank). The NMI handler in crt0.asm captures this automatically into pad_keys[]. Your code never touches hardware registers directly.

padHeld vs padPressed

u16 held = padHeld(0);      // Buttons held RIGHT NOW (every frame)
u16 pressed = padPressed(0); // Buttons pressed THIS FRAME ONLY (edge detection)

Use padHeld for continuous actions (movement, charging). Use padPressed for one-shot actions (jump, menu select, pause toggle).

Button Bitmask

Multiple buttons can be held simultaneously. Test with bitwise AND:

if (pad & KEY_A) { /* A is held */ }
if ((pad & KEY_L) && (pad & KEY_R)) { /* both shoulders held */ }

Modules Used

Module	Why it's here
console	consoleInit(), WaitForVBlank(), NMI handler setup
sprite	OAM buffer (required by NMI handler even with no visible sprites)
dma	DMA transfers used internally by console init
background	BG layer configuration
text	textInit(), textPrintAt(), textFlush() for button name display
input	padHeld(), padPressed() for reading controller state

Build & Run

cd $OPENSNES_HOME
make -C examples/input/controller

Open controller.sfc in Mesen2 and press buttons.