1 files changed, 531 insertions, 0 deletions
diff --git a/src/engine/link/ir_core.asm b/src/engine/link/ir_core.asm
new file mode 100644
index 0000000..ab9eaae
--- /dev/null
+++ b/src/engine/link/ir_core.asm
@@ -0,0 +1,531 @@
+; if carry flag is set, only delays
+; if carry not set:
+; - set rRP to $c1, wait;
+; - set rRP to $c0, wait;
+; - return
+Func_19674:
+	jr c, .delay_once
+	ld [hl], $c1
+	ld a, 5
+	jr .loop_delay_1 ; jump to possibly to add more cycles?
+.loop_delay_1
+	dec a
+	jr nz, .loop_delay_1
+	ld [hl], $c0
+	ld a, 14
+	jr .loop_delay_2 ; jump to possibly to add more cycles?
+.loop_delay_2
+	dec a
+	jr nz, .loop_delay_2
+	ret
+
+.delay_once
+	ld a, 21
+	jr .loop_delay_3 ; jump to possibly to add more cycles?
+.loop_delay_3
+	dec a
+	jr nz, .loop_delay_3
+	nop
+	ret
+
+; input a = byte to transmit through IR
+TransmitByteThroughIR:
+	push hl
+	ld hl, rRP
+	push de
+	push bc
+	ld b, a
+	scf  ; carry set
+	call Func_19674
+	or a ; carry not set
+	call Func_19674
+	ld c, 8
+	ld c, 8 ; number of input bits
+.loop
+	ld a, $00
+	rr b
+	call Func_19674
+	dec c
+	jr nz, .loop
+	pop bc
+	pop de
+	pop hl
+	ldh a, [rJOYP]
+	bit 1, a ; P11
+	jr z, ReturnZFlagUnsetAndCarryFlagSet
+	xor a ; return z set
+	ret
+
+; same as ReceiveByteThroughIR but
+; returns $0 in a if there's an error in IR
+ReceiveByteThroughIR_ZeroIfUnsuccessful:
+	call ReceiveByteThroughIR
+	ret nc
+	xor a
+	ret
+
+; returns carry if there's some time out
+; and output in register a of $ff
+; otherwise returns in a some sequence of bits
+; related to how rRP sets/unsets bit 1
+ReceiveByteThroughIR:
+	push de
+	push bc
+	push hl
+
+; waits for bit 1 in rRP to be unset
+; up to $100 loops
+	ld b, 0
+	ld hl, rRP
+.wait_ir
+	bit 1, [hl]
+	jr z, .ok
+	dec b
+	jr nz, .wait_ir
+	; looped around $100 times
+	; return $ff and carry set
+	pop hl
+	pop bc
+	pop de
+	scf
+	ld a, $ff
+	ret
+
+.ok
+; delay for some cycles
+	ld a, 15
+.loop_delay
+	dec a
+	jr nz, .loop_delay
+
+; loop for each bit
+	ld e, 8
+.loop
+	ld a, $01
+	; possibly delay cycles?
+	ld b, 9
+	ld b, 9
+	ld b, 9
+	ld b, 9
+
+; checks for bit 1 in rRP
+; if in any of the checks it is unset,
+; then a is set to 0
+; this is done a total of 9 times
+	bit 1, [hl]
+	jr nz, .asm_196ec
+	xor a
+.asm_196ec
+	bit 1, [hl]
+	jr nz, .asm_196f1
+	xor a
+.asm_196f1
+	dec b
+	jr nz, .asm_196ec
+	; one bit received
+	rrca
+	rr d
+	dec e
+	jr nz, .loop
+	ld a, d ; has bits set for each "cycle" that bit 1 was not unset
+	pop hl
+	pop bc
+	pop de
+	or a
+	ret
+
+ReturnZFlagUnsetAndCarryFlagSet:
+	ld a, $ff
+	or a ; z not set
+	scf  ; carry set
+	ret
+
+; called when expecting to transmit data
+Func_19705:
+	ld hl, rRP
+.asm_19708
+	ldh a, [rJOYP]
+	bit 1, a
+	jr z, ReturnZFlagUnsetAndCarryFlagSet
+	ld a, $aa ; request
+	call TransmitByteThroughIR
+	push hl
+	pop hl
+	call ReceiveByteThroughIR_ZeroIfUnsuccessful
+	cp $33 ; acknowledge
+	jr nz, .asm_19708
+	xor a
+	ret
+
+; called when expecting to receive data
+Func_1971e:
+	ld hl, rRP
+.asm_19721
+	ldh a, [rJOYP]
+	bit 1, a
+	jr z, ReturnZFlagUnsetAndCarryFlagSet
+	call ReceiveByteThroughIR_ZeroIfUnsuccessful
+	cp $aa ; request
+	jr nz, .asm_19721
+	ld a, $33 ; acknowledge
+	call TransmitByteThroughIR
+	xor a
+	ret
+
+ReturnZFlagUnsetAndCarryFlagSet2:
+	jp ReturnZFlagUnsetAndCarryFlagSet
+
+TransmitIRDataBuffer:
+	call Func_19705
+	jr c, ReturnZFlagUnsetAndCarryFlagSet2
+	ld a, $49
+	call TransmitByteThroughIR
+	ld a, $52
+	call TransmitByteThroughIR
+	ld hl, wIRDataBuffer
+	ld c, 8
+	jr TransmitNBytesFromHLThroughIR
+
+ReceiveIRDataBuffer:
+	call Func_1971e
+	jr c, ReturnZFlagUnsetAndCarryFlagSet2
+	call ReceiveByteThroughIR
+	cp $49
+	jr nz, ReceiveIRDataBuffer
+	call ReceiveByteThroughIR
+	cp $52
+	jr nz, ReceiveIRDataBuffer
+	ld hl, wIRDataBuffer
+	ld c, 8
+	jr ReceiveNBytesToHLThroughIR
+
+; hl = start of data to transmit
+; c = number of bytes to transmit
+TransmitNBytesFromHLThroughIR:
+	ld b, $0
+.loop_data_bytes
+	ld a, b
+	add [hl]
+	ld b, a
+	ld a, [hli]
+	call TransmitByteThroughIR
+	jr c, .asm_1977c
+	dec c
+	jr nz, .loop_data_bytes
+	ld a, b
+	cpl
+	inc a
+	call TransmitByteThroughIR
+.asm_1977c
+	ret
+
+; hl = address to write received data
+; c = number of bytes to be received
+ReceiveNBytesToHLThroughIR:
+	ld b, 0
+.loop_data_bytes
+	call ReceiveByteThroughIR
+	jr c, ReturnZFlagUnsetAndCarryFlagSet2
+	ld [hli], a
+	add b
+	ld b, a
+	dec c
+	jr nz, .loop_data_bytes
+	call ReceiveByteThroughIR
+	add b
+	or a
+	jr nz, ReturnZFlagUnsetAndCarryFlagSet2
+	ret
+
+; disables interrupts, and sets joypad and IR communication port
+; switches to CGB normal speed
+StartIRCommunications:
+	di
+	call SwitchToCGBNormalSpeed
+	ld a, P14
+	ldh [rJOYP], a
+	ld a, $c0
+	ldh [rRP], a
+	ret
+
+; reenables interrupts, and switches CGB back to double speed
+CloseIRCommunications:
+	ld a, P14 | P15
+	ldh [rJOYP], a
+.wait_vblank_on
+	ldh a, [rSTAT]
+	and STAT_LCDC_STATUS
+	cp STAT_ON_VBLANK
+	jr z, .wait_vblank_on
+.wait_vblank_off
+	ldh a, [rSTAT]
+	and STAT_LCDC_STATUS
+	cp STAT_ON_VBLANK
+	jr nz, .wait_vblank_off
+	call SwitchToCGBDoubleSpeed
+	ei
+	ret
+
+; set rRP to 0
+ClearRP:
+	ld a, $00
+	ldh [rRP], a
+	ret
+
+; expects to receive a command (IRCMD_* constant)
+; in wIRDataBuffer + 1, then calls the subroutine
+; corresponding to that command
+ExecuteReceivedIRCommands:
+	call StartIRCommunications
+.loop_commands
+	call ReceiveIRDataBuffer
+	jr c, .error
+	jr nz, .loop_commands
+	ld hl, wIRDataBuffer + 1
+	ld a, [hl]
+	ld hl, .CmdPointerTable
+	cp NUM_IR_COMMANDS
+	jr nc, .loop_commands ; invalid command
+	call .JumpToCmdPointer ; execute command
+	jr .loop_commands
+.error
+	call CloseIRCommunications
+	xor a
+	scf
+	ret
+
+.JumpToCmdPointer
+	add a ; *2
+	add l
+	ld l, a
+	ld a, 0
+	adc h
+	ld h, a
+	ld a, [hli]
+	ld h, [hl]
+	ld l, a
+.jp_hl
+	jp hl
+
+.CmdPointerTable
+	dw .Close                ; IRCMD_CLOSE
+	dw .ReturnWithoutClosing ; IRCMD_RETURN_WO_CLOSING
+	dw .TransmitData         ; IRCMD_TRANSMIT_DATA
+	dw .ReceiveData          ; IRCMD_RECEIVE_DATA
+	dw .CallFunction         ; IRCMD_CALL_FUNCTION
+
+; closes the IR communications
+; pops hl so that the sp points
+; to the return address of ExecuteReceivedIRCommands
+.Close
+	pop hl
+	call CloseIRCommunications
+	or a
+	ret
+
+; returns without closing the IR communications
+; will continue the command loop
+.ReturnWithoutClosing
+	or a
+	ret
+
+; receives an address and number of bytes
+; and transmits starting at that address
+.TransmitData
+	call Func_19705
+	ret c
+	call LoadRegistersFromIRDataBuffer
+	jp TransmitNBytesFromHLThroughIR
+
+; receives an address and number of bytes
+; and writes the data received to that address
+.ReceiveData
+	call LoadRegistersFromIRDataBuffer
+	ld l, e
+	ld h, d
+	call ReceiveNBytesToHLThroughIR
+	jr c, .asm_19812
+	sub b
+	call TransmitByteThroughIR
+.asm_19812
+	ret
+
+; receives an address to call, then stores
+; the registers in the IR data buffer
+.CallFunction
+	call LoadRegistersFromIRDataBuffer
+	call .jp_hl
+	call StoreRegistersInIRDataBuffer
+	ret
+
+; returns carry set if request sent was not acknowledged
+TrySendIRRequest:
+	call StartIRCommunications
+	ld hl, rRP
+	ld c, 4
+.send_request
+	ld a, $aa ; request
+	push bc
+	call TransmitByteThroughIR
+	push bc
+	pop bc
+	call ReceiveByteThroughIR_ZeroIfUnsuccessful
+	pop bc
+	cp $33 ; acknowledgement
+	jr z, .received_ack
+	dec c
+	jr nz, .send_request
+	scf
+	jr .close
+
+.received_ack
+	xor a
+.close
+	push af
+	call CloseIRCommunications
+	pop af
+	ret
+
+; returns carry set if request was not received
+TryReceiveIRRequest:
+	call StartIRCommunications
+	ld hl, rRP
+.wait_request
+	call ReceiveByteThroughIR_ZeroIfUnsuccessful
+	cp $aa ; request
+	jr z, .send_ack
+	ldh a, [rJOYP]
+	cpl
+	and P10 | P11
+	jr z, .wait_request
+	scf
+	jr .close
+
+.send_ack
+	ld a, $33 ; acknowledgement
+	call TransmitByteThroughIR
+	xor a
+.close
+	push af
+	call CloseIRCommunications
+	pop af
+	ret
+
+; sends request for other device to close current communication
+RequestCloseIRCommunication:
+	call StartIRCommunications
+	ld a, IRCMD_CLOSE
+	ld [wIRDataBuffer + 1], a
+	call TransmitIRDataBuffer
+;	fallthrough
+
+; calls CloseIRCommunications while preserving af
+SafelyCloseIRCommunications:
+	push af
+	call CloseIRCommunications
+	pop af
+	ret
+
+; sends a request for data to be transmitted
+; from the other device
+; hl = start of data to request to transmit
+; de = address to write data received
+; c = length of data
+RequestDataTransmissionThroughIR:
+	ld a, IRCMD_TRANSMIT_DATA
+	call TransmitRegistersThroughIR
+	push de
+	push bc
+	call Func_1971e
+	pop bc
+	pop hl
+	jr c, SafelyCloseIRCommunications
+	call ReceiveNBytesToHLThroughIR
+	jr SafelyCloseIRCommunications
+
+; transmits data to be written in the other device
+; hl = start of data to transmit
+; de = address for other device to write data
+; c = length of data
+RequestDataReceivalThroughIR:
+	ld a, IRCMD_RECEIVE_DATA
+	call TransmitRegistersThroughIR
+	call TransmitNBytesFromHLThroughIR
+	jr c, SafelyCloseIRCommunications
+	call ReceiveByteThroughIR
+	jr c, SafelyCloseIRCommunications
+	add b
+	jr nz, .asm_1989e
+	xor a
+	jr SafelyCloseIRCommunications
+.asm_1989e
+	call ReturnZFlagUnsetAndCarryFlagSet
+	jr SafelyCloseIRCommunications
+
+; first stores all the current registers in wIRDataBuffer
+; then transmits it through IR
+TransmitRegistersThroughIR:
+	push hl
+	push de
+	push bc
+	call StoreRegistersInIRDataBuffer
+	call StartIRCommunications
+	call TransmitIRDataBuffer
+	pop bc
+	pop de
+	pop hl
+	ret nc
+	inc sp
+	inc sp
+	jr SafelyCloseIRCommunications
+
+; stores af, hl, de and bc in wIRDataBuffer
+StoreRegistersInIRDataBuffer:
+	push de
+	push hl
+	push af
+	ld hl, wIRDataBuffer
+	pop de
+	ld [hl], e ; <- f
+	inc hl
+	ld [hl], d ; <- a
+	inc hl
+	pop de
+	ld [hl], e ; <- l
+	inc hl
+	ld [hl], d ; <- h
+	inc hl
+	pop de
+	ld [hl], e ; <- e
+	inc hl
+	ld [hl], d ; <- d
+	inc hl
+	ld [hl], c ; <- c
+	inc hl
+	ld [hl], b ; <- b
+	ret
+
+; loads all the registers that were stored
+; from StoreRegistersInIRDataBuffer
+LoadRegistersFromIRDataBuffer:
+	ld hl, wIRDataBuffer
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	inc hl
+	push de
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	inc hl
+	push de
+	ld e, [hl]
+	inc hl
+	ld d, [hl]
+	inc hl
+	ld c, [hl]
+	inc hl
+	ld b, [hl]
+	pop hl
+	pop af
+	ret