diff --git a/.gitignore b/.gitignore
new file mode 100644
index 0000000..b150859
--- /dev/null
+++ b/.gitignore
@@ -0,0 +1,4 @@
+*.pyc
+.env
+.3nv
+*egg-info*
diff --git a/src/escapelib/game.py b/src/escapelib/game.py
index c8872ed..ca3903d 100644
--- a/src/escapelib/game.py
+++ b/src/escapelib/game.py
@@ -25,7 +25,7 @@ class Game(six.with_metaclass(IOMeta)):
         # Configure Serial
         if self.__bus_port__ is not None:
             self.__services__.append(
-                SerialService(self.__bus_port__, self.__bus_baud__,
+                SerialService(self, self.__bus_port__, self.__bus_baud__,
                               self.__bus_power_enable__,
                               self.__bus_tx_enable__))
 
diff --git a/src/escapelib/hdlc/__init__.py b/src/escapelib/hdlc/__init__.py
new file mode 100644
index 0000000..6014917
--- /dev/null
+++ b/src/escapelib/hdlc/__init__.py
@@ -0,0 +1 @@
+from .protocol import HDLCProtocol
diff --git a/src/escapelib/hdlc/command.py b/src/escapelib/hdlc/command.py
new file mode 100644
index 0000000..e27385d
--- /dev/null
+++ b/src/escapelib/hdlc/command.py
@@ -0,0 +1,36 @@
+class HDLCCommand(object):
+    """Contains up to seven HDLCFrames."""
+    def __init__(self, bus_id, data):
+        self._frames = []
+        self._last_ack_idx = 0
+        self._peer_state = None
+        self._response = []
+        self.deferred = None
+        num_frames = ceil_div(len(data), FRAME_DATA_CAPACITY)
+        if num_frames is 0:
+            num_frames = 1
+        for i in range(num_frames):
+            start = i*FRAME_DATA_CAPACITY
+            end = start+FRAME_DATA_CAPACITY
+            self._frames.append(
+                HDLCFrame.iframe(bus_id, data[start:end], i, poll))
+
+    def rx_frame(self, frame):
+        """Adjust peer-recv value, accept data."""
+        num_ackd_frames = (frame.r_seq - self._peer_state.recv) % 8
+        self._last_ack_idx += num_ackd_frames
+        self._peer_state.recv = frame.r_seq
+        if frame.payload is not None:
+            self._response.append(frame.payload)
+        else:
+            self._response.append(frame.is_rr())
+
+    def do_callback(self):
+        self.deferred.callback(self._response)
+
+    def register_peerstate(self, peer_state):
+        """Link this command to remote state on peer to track s_seq, r_seq."""
+        self._peer_state = peer_state
+
+    def unacked_frames(self, frame):
+        return self._frames[self._last_ack_idx:]
diff --git a/src/escapelib/hdlc/exceptions.py b/src/escapelib/hdlc/exceptions.py
new file mode 100644
index 0000000..d272656
--- /dev/null
+++ b/src/escapelib/hdlc/exceptions.py
@@ -0,0 +1,5 @@
+class HDLCError(Exception):
+    pass
+
+class HDLCInvalidFrame(HDLCError):
+    pass
diff --git a/src/escapelib/hdlc/exchange.py b/src/escapelib/hdlc/exchange.py
new file mode 100644
index 0000000..50e3518
--- /dev/null
+++ b/src/escapelib/hdlc/exchange.py
@@ -0,0 +1,42 @@
+from escapelib.util import ceil_div
+
+class HDLCExchange(object):
+    """Contains one or more HDLCTransactions."""
+    def __init__(self, bus_id, data):
+        self.protocol = None
+        self.deferred = None
+        self._rseq = 0 # Last rx'd packet from remote
+        self._transactions = []
+        num_transactions = ceil_div(len(data),
+                                    TRANSACTION_DATA_CAPACITY)
+        if num_transactions is 0:
+            num_transactions = 1
+        for i in range(num_transactions):
+            start = i*TRANSACTION_DATA_CAPACITY
+            end = start+TRANSACTION_DATA_CAPACITY
+            self._transactions.append(
+                HDLCTransaction(bus_id, data[start:end]))
+
+    def do_frame(self, data):
+        frame = HDLCFrame.parse(data)
+        self._rseq = frame.r_seq
+        if (self._rseq >= len(self._transactions[self._cur_trans]) or
+            self._rseq == 0):  # _rseq is 0 when max packets in-flight
+                               # are ack'd
+            self._cur_trans += 1
+            if self._cur_trans >= len(self._trasactions):
+                self.deferred.callback(self.
+        if frame.final:
+            self.protocol._lock.release()
+
+
+    def __len__(self):
+        return len(self._transactions)
+
+    def __iter__(self):
+        self._cur_trans = 0
+        self._rseq = 0
+        return self._transactions.__iter__(self)
+
+    def __next__(self):
+        return self._transactions[self._cur_trans][self._next_frame:]
diff --git a/src/escapelib/hdlc/frame.py b/src/escapelib/hdlc/frame.py
new file mode 100644
index 0000000..62858fd
--- /dev/null
+++ b/src/escapelib/hdlc/frame.py
@@ -0,0 +1,177 @@
+from binascii import hexlify
+
+from .util import hdlc_escape, hdlc_crc
+
+CLIENT_MAX_BUFFER = 128
+HDLC_FRAME_OVERHEAD = 6  # Flag, Addr, Ctrl, FCS1, FCS2, Flag
+FRAME_DATA_CAPACITY = CLIENT_MAX_BUFFER - HDLC_FRAME_OVERHEAD
+TRANSACTION_DATA_CAPACITY = FRAME_DATA_CAPACITY * 7
+FLAG = b'\x7e'
+
+S_FRAME_TYPE_MASK = (0x3 << 2)
+S_FRAME_TYPE_RR = 0
+S_FRAME_TYPE_REJ = 1
+S_FRAME_TYPE_RNR = 2
+S_FRAME_TYPE_SREJ = 3
+
+POLL = FINAL = 1 << 4
+
+S_SEQ_MASK = (0x7 << 1)
+S_SEQ_OFFSET = 1
+R_SEQ_MASK = (0x7 << 5)
+R_SEQ_OFFSET = 5
+
+S_FRAME_MASK = 1
+U_FRAME_MASK = 3
+
+class HDLCFrame(object):
+
+    def __init__(self, frame_data=None, has_fcs=False):
+        if frame_data is None:
+            self._data = bytearray(2)
+        else:
+            self._data = bytearray(frame_data).strip(FLAG)
+            if has_fcs:
+                self._data = self._data[:-2]
+
+    @classmethod
+    def iframe(cls, address, payload, s_seq=0, poll=True):
+        frame = cls()
+        frame.is_iframe(True)
+        frame.address = address
+        frame.payload = payload
+        frame.s_seq = s_seq
+        frame.poll = poll
+        return frame
+
+    @classmethod
+    def sframe(cls, address, stype=S_FRAME_TYPE_RR, r_seq=0, poll=True):
+        frame = cls()
+        frame.is_sframe(True)
+        frame.address = address
+        frame.r_seq = r_seq
+        frame.poll = poll
+        frame.s_frame_type = stype
+        return frame
+
+    @classmethod
+    def uframe(cls, *args, **kwargs):
+        raise NotImplementedError
+
+    @classmethod
+    def parse(cls, frame_data):
+        frame_data = hdlc_unescape(frame_data)
+        if hdlc_check_fcs(frame_data):
+            return HDLCFrame(frame_data, has_fcs=True)
+        raise HDLCInvalidFrame("FCS Check Failed")
+
+    @property
+    def address(self):
+        return self._data[0]
+
+    @address.setter
+    def address(self, val):
+        self._data[0] = val & 0xff
+
+    @property
+    def control(self):
+        return self._data[1]
+
+    @control.setter
+    def control(self, val):
+        self._data[1] = val & 0xff
+
+    @property
+    def r_seq(self):
+        if self.is_uframe():
+            raise HDLCError("U-Frames have no N(R)")
+        return self.control & R_SEQ_MASK
+
+    @r_seq.setter
+    def r_seq(self, val):
+        self.control &= ~R_SEQ_MASK
+        self.control |= (val & 0x7) << R_SEQ_OFFSET
+
+    @property
+    def final(self):
+        return self.control & FINAL
+
+    @final.setter
+    def final(self, val):
+        if val:
+            self.control |= FINAL
+        else:
+            self.control &= ~FINAL
+
+    poll = final
+
+    @property
+    def s_seq(self):
+        if not self.is_iframe():
+            raise HDLCError("Only I-frames have N(S)")
+        self.control & S_SEQ_MASK
+
+    @s_seq.setter
+    def s_seq(self, val):
+        self.control &= ~S_SEQ_MASK
+        self.control |= (val & 0x7) << S_SEQ_OFFSET
+
+    def is_iframe(self, force=False):
+        if force:
+            self.control &= ~U_FRAME_MASK
+        return not self.control & S_FRAME_MASK
+
+    def is_sframe(self, force=False):
+        if force:
+            self.control &= ~U_FRAME_MASK
+            self.control |= S_FRAME_MASK
+        return (self.control & U_FRAME_MASK == S_FRAME_MASK)
+
+    def is_uframe(self):
+        return self.control & U_FRAME_MASK == U_FRAME_MASK
+
+    def is_rr(self):
+        return self.is_sframe and self.sframe_type == S_FRAME_TYPE_RR
+
+    def is_rnr(self):
+        return self.is_sframe and self.sframe_type == S_FRAME_TYPE_RNR
+
+    @property
+    def sframe_type(self):
+        if not self.is_sframe():
+            raise HDLCError("Non-sframe has no sframe type")
+        return self.control & S_FRAME_TYPE_MASK
+
+    @sframe_type.setter
+    def sframe_type(self, val):
+        self.control &= ~S_FRAME_TYPE_MASK
+        self.control |= val & 0x3
+
+    @property
+    def payload(self):
+        if self.is_sframe():
+            raise HDLCError("S-frame has no payload")
+        return self._data[2:]
+
+    @payload.setter
+    def payload(self, val):
+        if self.is_sframe():
+            raise HDLCError("S-frame has no payload")
+        new = bytearray(self._data[:2])
+        new.extend(val)
+        self._data = new
+
+    @property
+    def fcs(self):
+        return hdlc_crc(self._data)
+
+    def raw(self):
+        raw_frame = bytearray()
+        raw_frame.append(FLAG)
+        raw_frame.extend(hdlc_escape(self._data))
+        raw_frame.extend(hdlc_escape(self.fcs))
+        raw_frame.append(FLAG)
+        return raw_frame
+
+    def __repr__(self):
+        return hexlify(self.raw())
diff --git a/src/escapelib/hdlc/peer.py b/src/escapelib/hdlc/peer.py
new file mode 100644
index 0000000..10eebb1
--- /dev/null
+++ b/src/escapelib/hdlc/peer.py
@@ -0,0 +1,7 @@
+import attr
+
+@attr.s
+class HDLCPeerState(object):
+    send = attr.ib(default=0)
+    recv = attr.ib(default=0)
+    pending = attr.ib(default=attr.Factory(list))
diff --git a/src/escapelib/hdlc/protocol.py b/src/escapelib/hdlc/protocol.py
new file mode 100644
index 0000000..de34551
--- /dev/null
+++ b/src/escapelib/hdlc/protocol.py
@@ -0,0 +1,64 @@
+from twisted.internet import defer, protocol
+from twisted.internet.serialport import SerialPort
+
+from .command import HDLCCommand
+from .exchange import HDLCExchange
+from .frame import FLAG
+
+COMMAND_QUEUE = defer.DeferredQueue()
+
+def hdlc_submit_command(bus_id, packet=None):
+    command = HDLCCommand(bus_id, packet=packet)
+    command.deferred = defer.deferred()
+    COMMAND_QUEUE.put(ex)
+    return command.deferred
+
+class HDLCProtocol(protocol.Protocol):
+
+    def __init__(self, bus_port, **kwargs):
+        self._serial = SerialPort(bus_port, **kwargs)
+        self._token_lock = defer.DeferredLock()
+        self._command_lock = defer.DeferredLock()
+        self._rx_buf = bytearray()
+        self._rx_frames = []
+        self._peer_state = {}
+
+    def dataReceived(self, data):
+        print("RX:", hexlify(data), data)
+        if not FLAG in data:
+            self._rx_buf.extend(data)
+        else:
+            for byte in data:
+                if byte == b'\x7e':
+                    if len(self._buf) > 0:
+                        self.service_rx_frame(self._buf)
+                        self._buf = bytearray()
+                else:
+                    self._buf.append(byte)
+
+    def service_rx_frame(self, data):
+        frame = HDLCFrame.parse(data)
+        if frame is None:
+            return
+        self._cmd.rx_frame(frame)
+        if frame.final:
+            self._token_lock.release()
+
+    @defer.inlineCallbacks
+    def service_command(bus_id, data):
+        while True:
+            self._cmd = yield COMMAND_QUEUE.get()
+            peer_state = self._peer_state[cmd.bus_id]
+            self._cmd.register_peerstate(peer_state)
+            while True:
+                yield self._token_lock.acquire()
+                frames = self._cmd.unacked_frames()[:7]
+                if not frames:
+                    cmd.do_callback()
+                    break
+                frames[-1].poll = True  # Give up the token on last frame
+                for frame in frames:
+                    frame.s_seq = peer_state.send
+                    frame.r_seq = peer_state.recv
+                    self.sendSomeData(frame)
+                    peer_state.send += 1
diff --git a/src/escapelib/hdlc/util.py b/src/escapelib/hdlc/util.py
new file mode 100644
index 0000000..b890c91
--- /dev/null
+++ b/src/escapelib/hdlc/util.py
@@ -0,0 +1,34 @@
+import crcmod
+
+def hdlc_check_fcs(frame):
+    frame = frame.strip(FLAG)
+    l_crc = hdlc_crc(frame[:-2])
+    r_crc = frame[-2:]
+    return l_crc == r_crc
+
+def hdlc_crc(val):
+    crc16 = crcmod.predefined.Crc('xmodem')
+    crc16.update(val)
+    return crc16.digest()
+
+def hdlc_escape(data):  # type: (bytearray) -> bytearray
+    r = bytearray()
+    for i in data:
+        if i in [0x7e, 0x7d]:
+            r.append(0x7d)
+            r.append(i & ~(1 << 5))
+        else:
+            r.append(i)
+    return r
+
+def hdlc_unescape(data):  # type: (bytearray) -> bytearray
+    r = bytearray()
+    i = 0
+    while i < len(data):
+        if data[i] == 0x7d:
+            r.append(data[i+1] | (1 << 5))
+            i += 2
+        else:
+            r.append(data[i])
+            i += 1
+    return r
diff --git a/src/escapelib/io.py b/src/escapelib/io.py
index c20a08b..e96692b 100644
--- a/src/escapelib/io.py
+++ b/src/escapelib/io.py
@@ -39,6 +39,7 @@ class IOptions(object):
     def __init__(self):
         self.inputs = []
         self.outputs = []
+        self.props = []
 
     def add_input(self, i):
         self.inputs.append(i)
@@ -46,6 +47,15 @@ class IOptions(object):
     def add_output(self, o):
         self.outputs.append(o)
 
+    def add_prop(self, p):
+        self.props.append(p)
+
+    def find_prop(self, b_id):
+        for p in self.props:
+            if p.bus_id == b_id:
+                return p
+        return None
+
     def find_output(self, o_str):
         for o in self.outputs:
             if o.name == o_str:
@@ -69,6 +79,8 @@ class IOMeta(type):
                 cls._io.add_output(attr)
             elif isinstance(attr, Input):
                 cls._io.add_input(attr)
+            elif isinstance(attr, Prop):
+                cls._io.add_prop(attr)
 
 class IO(object):
 
@@ -101,3 +113,6 @@ class Output(IO):
 
 class Sensor(IO):
     pass
+
+class Prop(object):
+    pass
diff --git a/src/escapelib/nbus.py b/src/escapelib/nbus.py
index 4155106..754a7d3 100644
--- a/src/escapelib/nbus.py
+++ b/src/escapelib/nbus.py
@@ -1,5 +1,6 @@
 """Serial Bus fuctionality for Trespassed."""
 
+from binascii import hexlify
 from enum import IntEnum
 from functools import wraps
 from time import time
@@ -8,7 +9,9 @@ import attr
 import crcmod.predefined
 import six
 
-from escapelib.io import Input, Output, Sensor, IOMeta
+from escapelib import io
+#from escapelib.hdlc import hdlc_query_frame, HDLCFrame
+from escapelib.packet import process_packet
 from escapelib.status import set_status
 from escapelib.util import delay
 
@@ -21,17 +24,100 @@ from twisted.python import log
 WATCHDOG = {}
 WATCHDOG_TIMEOUT = 30
 
-__all__ = ('SerialService', 'on_input', 'on_puzzle', 'Prop', 'Input', 'Output')
+__all__ = ('SerialService', 'Prop', 'Input', 'Output')
 
-class PacketType(IntEnum):
-    Keepalive = 0
-    Input = 1
-    Output = 2
-    Solved = 3
-    Failed = 4
-    Log = 5
 
-class Prop(six.with_metaclass(IOMeta)):
+class NBusProtocol(protocol.Protocol):
+    _buf = b'' # type: bytes
+    _escape = False
+
+    def __init__(self, service):
+        self._service = service
+
+    def dataReceived(self, data):
+        print("RX:", hexlify(data), data)
+        for byte in data:
+            if self._escape:
+                escaped_byte = ord(byte) & ~(1 << 5)
+                if escaped_byte not in b'\x7d\x7e':
+                    log.msg(
+                        'Unnecessary escaped value: {}'.format(
+                            escaped_byte))
+                self._buf += escaped_byte
+                self._escape = False
+            elif byte == b'\x7d':
+                self._escape = True
+            elif byte == b'\x7e':
+                if len(self._buf) is 0:
+                    return
+                frame = HDLCFrame.parse(self._buf)
+                if frame:
+                    print("Packet: ", hexlify(frame.payload))
+                self._clear_buf()
+                self._service.mutex.release()
+            else:
+                self._buf += byte
+
+    def _clear_buf(self):
+        self._buf = b''
+
+
+NBUS_QUEUE = defer.DeferredQueue()
+
+class SerialService(service.Service):
+    """Service wrapper for twisted.internet.serialport."""
+
+    _serial = None  # type: SerialPort
+    _port = None    # type: str
+    bypass = False  # type: bool
+    mutex = defer.DeferredLock()
+
+    def __init__(self, game, port='/dev/ttyS0', baudrate=1000000,
+                 power_gpio=None, tx_enable_gpio=None):
+        # type: (str, int) -> None
+        """Instanatiate SerialPort handling service."""
+        self._port = port
+        self._baud = baudrate
+        self._game = game
+
+    def startService(self):
+        """Start the NBus serial handling service."""
+        try:
+            self._serial = SerialPort(
+                NBusProtocol(self), self._port, reactor, baudrate=self._baud)
+            reactor.callLater(0, self.do_bus_write)
+            reactor.callLater(0, self.queue_poll)
+        except IOError as e:
+            log.msg(
+                "Failed to initialize serial. NBUS disabled: {}".format(e))
+
+    def stopService(self):
+        """Stop the NBus serial handling service."""
+        self._serial.loseConnection()
+
+    @defer.inlineCallbacks
+    def do_bus_write(self):
+        while True:
+            frame = yield NBUS_QUEUE.get()
+            d = self.mutex.acquire()
+            def _release_mutex_on_timeout(garbage, timeout):
+                print("Timed out after {} seconds".format(timeout))
+                self.mutex.release()
+            d.addTimeout(1, reactor, onTimeoutCancel=_release_mutex_on_timeout)
+            yield d
+            print("Sending: ", hexlify(frame))
+            self._serial.writeSomeData(frame)
+
+    def queue_poll(self):
+        """Add a query frame for every registered prop to the queue."""
+        for prop in self._game._io.props:
+            pass
+            #print("Added ", hdlc_query_frame(prop.bus_id))
+            #NBUS_QUEUE.put(hdlc_query_frame(prop.bus_id))
+        reactor.callLater(5, self.queue_poll)
+
+
+class Prop(six.with_metaclass(io.IOMeta, io.Prop)):
 
     def __init__(self, bus_id, title=None):
         self.bus_id = bus_id
@@ -43,84 +129,14 @@ class Prop(six.with_metaclass(IOMeta)):
         if self.title is None:
             self.title = name.replace('_', ' ').capitalize()
 
-class Input(Input):
+
+class Input(io.Input):
     pass
 
-class Output(Output):
+
+class Output(io.Output):
     pass
 
-class Analog(Sensor):
+
+class Analog(io.Sensor):
     pass
-
-@attr.s
-class HDLCFrame(object):
-    _frame_data = attr.ib()
-
-    def is_valid(self):
-        r_crc = self._frame_data[-2:]
-        crc16 = crcmod.predefined.Crc('xmodem')
-        crc16.update(self._frame_data[:-2])
-        crc = crc16.digest()
-        return crc == r_crc
-
-class NBusProtocol(protocol.Protocol):
-    _buf = b'' # type: bytes
-    _escape = False
-
-    def dataReceived(self, data):
-        #log.msg("RX: {}".format(hexlify(data)))
-        for byte in data:
-            if self._escape:
-                escaped_byte = byte & ~(1 << 5)
-                if escaped_byte not in b'\x7d\x7e':
-                    log.msg(
-     'Warning: Unnecessary escaped value: {}'.format(escaped_byte))
-                self._buf += escaped_byte
-                self._escape = False
-            elif byte == b'\x7d':
-                self._escape = True
-            elif byte == b'\x7e' and len(self._buf) > 0:
-                self._check_crc()
-                self._buf = b''
-            else:
-                self._buf += byte
-
-    def _check_crc(self):
-        r_crc = self._buf[-2:]
-        crc16 = crcmod.predefined.Crc('xmodem')
-        crc16.update(packet[:-2])
-        crc = crc16.digest()
-        if crc != r_crc:
-            log.err("CRC Mismatch: {}".format(packet))
-            return
-
-    def _filter(self, packet):
-        pass
-
-
-class SerialService(service.Service):
-    """Service wrapper for twisted.internet.serialport."""
-
-    _serial = None  # type: SerialPort
-    _port = None    # type: str
-    bypass = False  # type: bool
-
-    def __init__(self, port='/dev/ttyS0', baudrate=1000000,
-                 power_gpio=None, tx_enable_gpio=None):
-        # type: (str, int) -> None
-        """Instanatiate SerialPort handling service."""
-        self._port = port
-        self._baud = baudrate
-
-    def startService(self):
-        """Start the NBus serial handling service."""
-        try:
-            self._serial = SerialPort(NBusProtocol(), self._port,
-                                      reactor, baudrate=self._baud)
-        except IOError as e:
-            log.msg(
-                "Failed to initialize serial. NBUS disabled: {}".format(e))
-
-    def stopService(self):
-        """Stop the NBus serial handling service."""
-        self._serial.loseConnection()
diff --git a/src/escapelib/packet.py b/src/escapelib/packet.py
new file mode 100644
index 0000000..f995f8a
--- /dev/null
+++ b/src/escapelib/packet.py
@@ -0,0 +1,28 @@
+from enum import IntEnum
+
+import attr
+
+class PacketType(IntEnum):
+    Keepalive = 0
+    InputChange = 1
+    InputRequest = 2
+    SensorRequest = 3
+    PuzzleSolved = 4
+    PuzzleFailed = 5
+    Log = 6
+
+@attr.s
+class Packet(object):
+    p_type = attr.ib()
+    payload = attr.ib()
+
+    @classmethod
+    def parse(cls, binary):
+        return cls(binary[0], binary[1:])
+
+def process_packet(game, b_id, data):
+    packet = Packet.parse(data)
+    if packet.p_type == PacketType.InputChange:
+        pass
+    elif packet.p_type == PacketType.PuzzleSolved:
+        pass
diff --git a/src/escapelib/util.py b/src/escapelib/util.py
index aa34ced..e7464aa 100644
--- a/src/escapelib/util.py
+++ b/src/escapelib/util.py
@@ -1,5 +1,7 @@
 """Utility Functions for Trespassed."""
 
+from __future__ import division
+
 from twisted.internet import reactor, task
 
 def delay(sec):
@@ -16,3 +18,10 @@ def quit_game():
     if not skip:
         reactor.stop()
     skip = False
+
+def ceil_div(dividend, divisor):
+    """Return ceiling division of divident/divisor."""
+
+    r = dividend // divisor
+    r += 1 if dividend % divisor else 0
+    return r