millfork/include/gb_joy.mfk

#if not(GAMEBOY)
#warn gb_joy module should be only used on Game Boy targets
#endif

import gb_hardware

#pragma zilog_syntax

// standard joystick driver for Game Boy

import joy

alias input_a = input_btn
byte input_b
byte input_select
byte input_start

void read_joy() {
    byte tmp
    reg_joypad = $20
    asm {
        ld a,(reg_joypad)
        ld a,(reg_joypad)
        ld a,(reg_joypad)
        ld a,(reg_joypad)
    }
    tmp = reg_joypad
    input_dx = 0
    input_dy = 0
    if tmp & 1 == 0 { input_dx += 1 }
    if tmp & 2 == 0 { input_dx -= 1 }
    if tmp & 4 == 0 { input_dy -= 1 }
    if tmp & 8 == 0 { input_dy += 1 }
    reg_joypad = $10
    asm {
        ld a,(reg_joypad)
        ld a,(reg_joypad)
        ld a,(reg_joypad)
        ld a,(reg_joypad)
    }
    
    tmp = reg_joypad ^ $ff
    input_a = (tmp & 1) // >> 0  
    input_b = (tmp & 2) >> 1
    input_select = (tmp & 4) >> 2
    input_start = (tmp & 8) >> 3
}