;----------------------------------------------------------------------------
;InitializePeriphUSB:
;Initializes ourself as a USB peripheral connected to...something.
;Inputs:        None
;Outputs:       Carry flag set if any issues.
InitializePeriphUSB:
        bcall(810Eh) ;_KillUSB
        ret c
        ld a,80h
        out (57h),a
        xor a
        out (4Ch),a
        ld a,1
        out (5Bh),a
        xor a
        in a,(4Ch)
        ld a,2
        out (54h),a
        ld a,20h
        out (4Ah),a
        xor a
        out (4Bh),a
        in a,(3Ah)
        bit 3,a
        jr z,port3AhReset1
        ld a,20h
        out (4Bh),a
port3AhReset1:
        xor a
        out (54h),a
        ld a,42h
        out (36h),a
        xor a
        out (37h),a
        ld a,1
        out (38h),a
timerWait:
        in a,(4)
        bit 7,a
        jr z,timerWait
        in a,(3Ah)
        bit 3,a
        jr z,port3AhReset2
        ld a,44h
        out (54h),a
port3AhReset2:
        ld a,0C4h
        out (54h),a
        ld a,8
        out (4Ch),a
        ld de,0FFFFh
port5AhLoop:
        dec de
        ld a,d
        or e
        scf
        ret z
        in a,(4Ch)
        cp 1Ah
        jr z,port5AhDone
        cp 5Ah
        jr nz,port5AhLoop
port5AhDone:
        ld a,0FFh
        out (87h),a
        xor a
        out (92h),a
        in a,(87h)
        ld a,0Eh
        out (89h),a
        ld a,5
        out (8Bh),a
        in a,(81h)
        or
        out (81h),a
        in a,(54h)
        or 1
        out (54h),a
        ld b,5
frameCounterLoop:
        ld de,0FFFFh
frameCounterLoop2:
        dec de
        ld a,d
        or e
        jr z,counterExpired
        in a,(8Ch)
        or a
        jr z,frameCounterLoop2
        ret
counterExpired:
        djnz frameCounterLoop
        scf
        ret
;----------------------------------------------------------------------------
;IsUSBAvailable:
;Returns whether USB communication MAY be available.
;Inputs:        None
;Outputs:       Carry flag set if USB is not available.
IsUSBAvailable:
        in a,(2)
        bit 5,a
        scf
        ret z
        ld a,(4Dh)
        or a
        bit 5,a
        ret z
        bit 6,a
        scf
        ret nz
        ccf
        ret
;----------------------------------------------------------------------------
;SendUSBData:
;Sends data over USB.
;Inputs:        HL => pointer in zone 1 (RAM pages 3\2) of data to send.
;               DE: number of bytes to send.
;Outputs:       DE bytes sent from HL.
;               Carry flag set if any issues.
SendUSBData:
        res 0,(iy+43h)
        bcall(50F2h)
        res 0,(iy+41h)
        res 5,(iy+41h)
        ret
;----------------------------------------------------------------------------
;ReceiveUSBDataWait:
;Receives data over USB (waits until data is received).
;Inputs:        HL => pointer in RAM to store data to.
;               BC: number of bytes to receive.
;Outputs:       BC bytes received to HL.
;               Carry flag set if any issues.
;Make sure you know how much you need to be receiving before calling.
;This is a blocking call and will not return until everything is received.
ReceiveUSBDataWait:
        ei
        halt
        in a,(4)
        bit 3,a
        scf
        ret z
        bit 5,(iy+41h)
        jr z,ReceiveUSBDataWait
;----------------------------------------------------------------------------
;ReceiveUSBData:
;Receives data over USB.
;Inputs:        5,(iy+41h) set by OS.
;               HL => pointer in RAM to store data to.
;               BC: number of bytes to receive.
;Outputs:       BC bytes received to HL.
;               Carry flag set if any issues.
;Make sure you know how much you need to be receiving before calling.
ReceiveUSBData:
	push bc
	push af
	xor a
	ld (9834h),a
	jr receive_data_ready
receive_big_loop:
	in a,(4)
	bit 3,a
	jr z,P2scfRet
	bit 5,(iy+41h)
	jr nz,receive_data_ready
	in a,(84h)
	bit 2,a
	jr nz,receiving_data
	bit 1,a
	jr z,restart_receive_loop
receiving_data:
	set 5,(iy+41h)
	xor a
	ld (9C27h),a
	jr receive_data_ready
restart_receive_loop:
	in a,(86h)
	bit 5,a
	jr nz,P2scfRet
	jr receive_big_loop
receive_data_ready:
	push bc
	push hl
	ld hl,40h
	or a
	sbc hl,bc
	pop hl
	ld b,c
	jr nc,receiveRest
	ld b,40h
receiveRest:
	call ReceiveUSBData_small
	ex de,hl
	pop hl
	jr c,P2scfRet
	or a
	ld b,0
	sbc hl,bc
	jr z,P2ret
	ld b,h
	ld c,l
	ex de,hl
	jr receive_big_loop
P2ret:	pop bc
	ld a,b
	pop bc
	ret
P2scfRet:
	pop af
	pop bc
	scf
	ret
ReceiveUSBData_small:
        ld a,b
        or a
        ret z
        ld a,40h
        cp b
        ret c
        ld a,b
        ld (9C80h),a
        ld a,(9C27h)
        or a
        jr z,ReceiveUSBData_continue
        cp b
        jr nc,ReceiveUSBData_continue
        ld b,a
        ld (9C80h),a
ReceiveUSBData_continue:
        in a,(8Fh)
        bit 2,a
        jp z,calcIsPeripheral
        xor a
        out (5Bh),a
        ld a,(9C27h)
        or a
        jr nz,startReceive
        ld a,1
        out (8Eh),a
        ld a,21h
        out (9Ah),a
        xor a
        in a,(9Ah)
        ld a,8
        out (93h),a
        xor a
        in a,(93h)
        ld a,0FFh
        out (89h),a
        xor a
        out (95h),a
        in a,(89h)
        ld a,0A1h
        out (8Bh),a
        in a,(94h)
        bit 2,a
        jp nz,receiveError
        bit 6,a
        jp nz,receiveError
        ld a,1
        out (5Bh),a
        ld a,(9C27h)
        or a
        jr nz,startReceive
        ld a,1
        out (8Eh),a
        in a,(94h)
        in a,(96h)
startReceive:
        push af
        ld a,(9C80h)
        ld b,a
        ld c,0
receiveLoop:
        in a,(0A1h)
        ld (hl),a
        inc hl
        inc c
        djnz receiveLoop
        ld a,1
        out (8Eh),a
        in a,(94h)
        bit 2,a
        jr nz,p1ReceiveError
        bit 6,a
        jr nz,p1ReceiveError
        pop af
        sub c
        ld (9C27h),a
        set 5,(iy+41h)
        ret nz
        ld a,1
        out (8Eh),a
        ld a,21h
        out (9Ah),a
        ld a,8
        out (93h),a
        xor a
        in a,(93h)
        ld a,0Eh
        out (89h),a
        xor a
        out (95h),a
        res 5,(iy+41h)
        xor a
        ld (9C27h),a
        res 0,(iy+41h)
        ld a,20h
        out (94h),a
        ld a,1
        out (5Bh),a
        ret
calcIsPeripheral:
        ld a,2
        out (8Eh),a
        in a,(94h)
        bit 6,a
        jr z,startReceive2
        and 0DFh
        out (94h),a
        pop af
        bcall(5257h) ;_KillUSBDevice
	jr receiveError
startReceive2:
        ld a,(9C27h)
        or a
        jr nz,startReceive3
        in a,(96h)
startReceive3:
        push af
        ld c,0
receivePeriphLoop:
        in a,(0A2h)
        ld (hl),a
        inc hl
        inc c
        djnz receivePeriphLoop
        ld a,2
        out (8Eh),a
        pop af
        sub c
        ld (9C27h),a
        ret nz
        xor a
        ld (9C27h),a
        in a,(94h)
        and 0FEh
        out (94h),a
        res 5,(iy+41h)
        ld a,0A1h
        ld (8Bh),a
        jr endReceive
p1ReceiveError:
        pop af
receiveError:
        res 5,(iy+41h)
        scf
endReceive:
        ei
        ld a,1
        out (5Bh),a
        res 0,(iy+41h)
        ret
;----------------------------------------------------------------------------