diff --git a/pycoax/coax/__init__.py b/pycoax/coax/__init__.py
index 31433d0..b144d46 100644
--- a/pycoax/coax/__init__.py
+++ b/pycoax/coax/__init__.py
@@ -2,6 +2,8 @@ from .__about__ import __version__
 
 from .interface1 import Interface1
 
+from .serial_interface import SerialInterface
+
 from .protocol import (
     PollAction,
     PollResponse,
diff --git a/pycoax/coax/interface.py b/pycoax/coax/interface.py
new file mode 100644
index 0000000..77ad984
--- /dev/null
+++ b/pycoax/coax/interface.py
@@ -0,0 +1,19 @@
+"""
+coax.interface
+~~~~~~~~~~~~~~
+"""
+
+class Interface:
+    def reset(self):
+        raise NotImplementedError
+
+    def transmit(self, words, repeat_count=None, repeat_offset=1):
+        raise NotImplementedError
+
+    def receive(self, length=None, timeout=None):
+        raise NotImplementedError
+
+    def transmit_receive(self, transmit_words, transmit_repeat_count=None,
+                         transmit_repeat_offset=1, receive_length=None,
+                         receive_timeout=None):
+        raise NotImplementedError
diff --git a/pycoax/coax/serial_interface.py b/pycoax/coax/serial_interface.py
new file mode 100644
index 0000000..0688bba
--- /dev/null
+++ b/pycoax/coax/serial_interface.py
@@ -0,0 +1,176 @@
+"""
+coax.serial_interface
+~~~~~~~~~~~~~~~~~~~~~
+"""
+
+import struct
+from sliplib import SlipWrapper, ProtocolError
+
+from .interface import Interface
+from .exceptions import InterfaceError, InterfaceTimeout, ReceiveError, ReceiveTimeout
+
+class SerialInterface(Interface):
+    def __init__(self, serial):
+        if serial is None:
+            raise ValueError('Serial port is required')
+
+        self.serial = serial
+
+        self.slip_serial = SlipSerial(self.serial)
+
+    def reset(self):
+        original_serial_timeout = self.serial.timeout
+
+        self.serial.reset_input_buffer()
+
+        self._write_message(bytes([0x01]))
+
+        self.serial.timeout = 5
+
+        try:
+            message = self._read_message()
+        finally:
+            self.serial.timeout = original_serial_timeout
+
+        if message[0] != 0x01:
+            raise _convert_error(message)
+
+        if len(message) != 4:
+            raise InterfaceError('Invalid reset response')
+
+        (major, minor, patch) = struct.unpack('BBB', message[1:])
+
+        return '{}.{}.{}'.format(major, minor, patch)
+
+    def transmit(self, words, repeat_count=None, repeat_offset=1):
+        message = bytes([0x02])
+
+        message += _pack_transmit_header(len(words), repeat_count, repeat_offset)
+        message += _pack_transmit_data(words)
+
+        self._write_message(message)
+
+        message = self._read_message()
+
+        if message[0] != 0x01:
+            raise _convert_error(message)
+
+    def receive(self, length=None, timeout=None):
+        timeout_milliseconds = self._calculate_timeout_milliseconds(timeout)
+
+        message = bytes([0x04])
+
+        message += _pack_receive_header(length, timeout_milliseconds)
+
+        self._write_message(message)
+
+        message = self._read_message()
+
+        if message[0] != 0x01:
+            raise _convert_error(message)
+
+        return _unpack_receive_response(message[1:])
+
+    def transmit_receive(self, transmit_words, transmit_repeat_count=None,
+                         transmit_repeat_offset=1, receive_length=None,
+                         receive_timeout=None):
+        timeout_milliseconds = self._calculate_timeout_milliseconds(receive_timeout)
+
+        message = bytes([0x06])
+
+        message += _pack_transmit_header(len(transmit_words), transmit_repeat_count,
+                                         transmit_repeat_offset)
+        message += _pack_transmit_data(transmit_words)
+        message += _pack_receive_header(receive_length, timeout_milliseconds)
+
+        self._write_message(message)
+
+        message = self._read_message()
+
+        if message[0] != 0x01:
+            raise _convert_error(message)
+
+        return _unpack_receive_response(message[1:])
+
+    def _calculate_timeout_milliseconds(self, timeout):
+        milliseconds = 0
+
+        if timeout:
+            if self.serial.timeout and timeout > self.serial.timeout:
+                raise ValueError('Timeout cannot be greater than serial timeout')
+
+            milliseconds = int(timeout * 1000)
+
+        return milliseconds
+
+    def _read_message(self):
+        try:
+            message = self.slip_serial.recv_msg()
+        except ProtocolError:
+            raise InterfaceError('SLIP protocol error')
+
+        if len(message) < 4:
+            raise InterfaceError('Invalid response message')
+
+        (length,) = struct.unpack(">H", message[:2])
+
+        if length != len(message) - 4:
+            raise InterfaceError('Response message length mismatch')
+
+        if length < 1:
+            raise InterfaceError('Empty response message')
+
+        return message[2:-2]
+
+    def _write_message(self, message):
+        self.slip_serial.send_msg(struct.pack(">H", len(message)) + message +
+                                  struct.pack(">H", 0))
+
+def _pack_transmit_header(length, repeat_count, repeat_offset):
+    repeat = ((repeat_offset << 15) | repeat_count) if repeat_count else 0
+
+    return struct.pack(">HH", length, repeat)
+
+def _pack_transmit_data(words):
+    bytes_ = bytearray()
+
+    for word in words:
+        bytes_ += struct.pack(">H", word)
+
+    return bytes_
+
+def _pack_receive_header(length, timeout_milliseconds):
+    return struct.pack(">HH", length or 0, timeout_milliseconds)
+
+def _unpack_receive_response(message):
+    pass
+
+def _convert_error(message):
+    # TODO
+
+    return InterfaceError('Unknown error')
+
+class SlipSerial(SlipWrapper):
+    """sliplib wrapper for pySerial."""
+
+    def send_bytes(self, packet):
+        """Sends a packet over the serial port."""
+        self.stream.write(packet)
+        self.stream.flush()
+
+    def recv_bytes(self):
+        """Receive data from the serial port."""
+        if self.stream.closed:
+            return b''
+
+        count = self.stream.in_waiting
+
+        if count:
+            return self.stream.read(count)
+
+        byte = self.stream.read(1)
+
+        if byte == b'':
+            raise InterfaceTimeout()
+
+        return byte
diff --git a/pycoax/tests/test_serial_interface.py b/pycoax/tests/test_serial_interface.py
new file mode 100644
index 0000000..56ded69
--- /dev/null
+++ b/pycoax/tests/test_serial_interface.py
@@ -0,0 +1,124 @@
+import unittest
+from unittest.mock import Mock
+import sliplib
+
+import context
+
+from coax import SerialInterface, InterfaceError, ReceiveError, ReceiveTimeout
+
+class SerialInterfaceResetTestCase(unittest.TestCase):
+    def setUp(self):
+        self.serial = Mock()
+
+        self.serial.timeout = None
+
+        self.interface = SerialInterface(self.serial)
+
+        self.interface._write_message = Mock()
+        self.interface._read_message = Mock(return_value=bytes.fromhex('01 01 02 03'))
+
+    def test_message_is_sent(self):
+        # Act
+        self.interface.reset()
+
+        # Assert
+        self.interface._write_message.assert_called_with(bytes.fromhex('01'))
+
+    def test_version_is_formatted_correctly(self):
+        self.assertEqual(self.interface.reset(), '1.2.3')
+
+    def test_timeout_is_restored_after_reset(self):
+        # Arrange
+        self.serial.timeout = 123
+
+        # Act
+        self.interface.reset()
+
+        # Assert
+        self.assertEqual(self.serial.timeout, 123)
+
+    def test_invalid_message_length_is_handled_correctly(self):
+        # Arrange
+        self.interface._read_message = Mock(return_value=bytes.fromhex('01 01'))
+
+        # Act and assert
+        with self.assertRaisesRegex(InterfaceError, 'Invalid reset response'):
+            self.interface.reset()
+
+    def test_error_is_handled_correctly(self):
+        # Arrange
+        self.interface._read_message = Mock(return_value=bytes.fromhex('02 01'))
+
+        # Act and assert
+        with self.assertRaisesRegex(InterfaceError, 'Invalid request message'):
+            self.interface.reset()
+
+# TODO...
+
+class SerialInterfaceReadMessageTestCase(unittest.TestCase):
+    def setUp(self):
+        self.serial = Mock()
+
+        self.interface = SerialInterface(self.serial)
+
+        self.interface.slip_serial = Mock()
+
+    def test(self):
+        # Arrange
+        self.interface.slip_serial.recv_msg = Mock(return_value=bytes.fromhex('00 04 01 02 03 04 00 00'))
+
+        # Act
+        message = self.interface._read_message()
+
+        # Assert
+        self.assertEqual(message, bytes.fromhex('01 02 03 04'))
+
+    def test_protocol_error_is_handled_correctly(self):
+        # Arrange
+        self.interface.slip_serial.recv_msg = Mock(side_effect=sliplib.ProtocolError)
+
+        # Act and assert
+        with self.assertRaisesRegex(InterfaceError, 'SLIP protocol error'):
+            self.interface._read_message()
+
+    def test_invalid_message_length_is_handled_correctly(self):
+        # Arrange
+        self.interface.slip_serial.recv_msg = Mock(return_value=bytes.fromhex('00'))
+
+        # Act and assert
+        with self.assertRaisesRegex(InterfaceError, 'Invalid response message'):
+            self.interface._read_message()
+
+    def test_message_length_mismatch_is_handled_correctly(self):
+        # Arrange
+        self.interface.slip_serial.recv_msg = Mock(return_value=bytes.fromhex('00 05 01 02 03 04 00 00'))
+
+        # Act and assert
+        with self.assertRaisesRegex(InterfaceError, 'Response message length mismatch'):
+            self.interface._read_message()
+
+    def test_empty_message_is_handled_correctly(self):
+        # Arrange
+        self.interface.slip_serial.recv_msg = Mock(return_value=bytes.fromhex('00 00 00 00'))
+
+        # Act and assert
+        with self.assertRaisesRegex(InterfaceError, 'Empty response message'):
+            self.interface._read_message()
+
+class SerialInterfaceWriteMessageTestCase(unittest.TestCase):
+    def setUp(self):
+        self.serial = Mock()
+
+        self.interface = SerialInterface(self.serial)
+
+        self.interface.slip_serial = Mock()
+
+    def test(self):
+        # Act
+        self.interface._write_message(bytes.fromhex('01 02 03 04'))
+
+        # Assert
+        self.interface.slip_serial.send_msg.assert_called_with(bytes.fromhex('00 04 01 02 03 04 00 00'))
+
+if __name__ == '__main__':
+    unittest.main()