diff --git a/artiq/coredevice/comm_generic.py b/artiq/coredevice/comm_generic.py
new file mode 100644
index 000000000..76548c992
--- /dev/null
+++ b/artiq/coredevice/comm_generic.py
@@ -0,0 +1,202 @@
+import struct
+import zlib
+import logging
+from enum import Enum
+from fractions import Fraction
+
+from artiq.language import units
+from artiq.coredevice.runtime import Environment
+from artiq.coredevice import runtime_exceptions
+from artiq.language import core as core_language
+from artiq.coredevice.rpc_wrapper import RPCWrapper
+
+
+logger = logging.getLogger(__name__)
+
+
+class _H2DMsgType(Enum):
+    LINK_MESSAGE = 1
+
+    REQUEST_IDENT = 2
+    SWITCH_CLOCK = 3
+
+    LOAD_OBJECT = 4
+    RUN_KERNEL = 5
+    
+
+class _D2HMsgType(Enum):
+    MESSAGE_UNRECOGNIZED = 1
+    LOG = 2
+
+    IDENT = 3
+    CLOCK_SWITCH_COMPLETED = 4
+    CLOCK_SWITCH_FAILED = 5
+
+    OBJECT_LOADED = 6
+    OBJECT_INCORRECT_LENGTH = 7
+    OBJECT_CRC_FAILED = 8
+    OBJECT_UNRECOGNIZED = 9
+
+    KERNEL_FINISHED = 10
+    KERNEL_STARTUP_FAILED = 11
+    KERNEL_EXCEPTION = 12
+
+    RPC_REQUEST = 13
+
+
+class UnsupportedDevice(Exception):
+    pass
+
+
+class CommGeneric:
+    # methods for derived classes to implement
+    def open(self):
+        """Opens the communication channel.
+        Must do nothing if already opened."""
+        raise NotImplementedError
+
+    def close(self):
+        """Closes the communication channel.
+        Must do nothing if already closed."""
+        raise NotImplementedError
+
+    def read(self, length):
+        """Reads exactly length bytes from the communication channel.
+        The channel is assumed to be opened."""
+        raise NotImplementedError
+
+    def write(self, data):
+        """Writes exactly length bytes to the communication channel.
+        The channel is assumed to be opened."""
+        raise NotImplementedError
+    #
+
+    def _read(self, length):
+        self.open()
+        return self.read(length)
+
+    def _write(self, data):
+        self.open()
+        self.write(data)
+
+    def _get_device_msg(self):
+        while True:
+            (reply, ) = struct.unpack("B", self._read(1))
+            msg = _D2HMsgType(reply)
+            if msg == _D2HMsgType.LOG:
+                (length, ) = struct.unpack(">h", self._read(2))
+                log_message = ""
+                for i in range(length):
+                    (c, ) = struct.unpack("B", self._read(1))
+                    log_message += chr(c)
+                logger.info("DEVICE LOG: %s", log_message)
+            else:
+                logger.debug("message received: %r", msg)
+                return msg
+
+    def get_runtime_env(self):
+        self._write(struct.pack(">lb", 0x5a5a5a5a,
+                                _H2DMsgType.REQUEST_IDENT.value))
+        msg = self._get_device_msg()
+        if msg != _D2HMsgType.IDENT:
+            raise IOError("Incorrect reply from device: {}".format(msg))
+        (reply, ) = struct.unpack("B", self._read(1))
+        runtime_id = chr(reply)
+        for i in range(3):
+            (reply, ) = struct.unpack("B", self._read(1))
+            runtime_id += chr(reply)
+        if runtime_id != "AROR":
+            raise UnsupportedDevice("Unsupported runtime ID: {}"
+                                    .format(runtime_id))
+        ref_freq_i, ref_freq_fn, ref_freq_fd = struct.unpack(
+            ">lBB", self._read(6))
+        ref_freq = (ref_freq_i + Fraction(ref_freq_fn, ref_freq_fd))*units.Hz
+        ref_period = 1/ref_freq
+        logger.debug("environment ref_period: %s", ref_period)
+        return Environment(ref_period)
+
+    def switch_clock(self, external):
+        self._write(struct.pack(
+            ">lbb", 0x5a5a5a5a, _H2DMsgType.SWITCH_CLOCK.value,
+            int(external)))
+        msg = self._get_device_msg()
+        if msg != _D2HMsgType.CLOCK_SWITCH_COMPLETED:
+            raise IOError("Incorrect reply from device: {}".format(msg))
+
+    def load(self, kcode):
+        self._write(struct.pack(
+            ">lblL",
+            0x5a5a5a5a, _H2DMsgType.LOAD_OBJECT.value,
+            len(kcode), zlib.crc32(kcode)))
+        self._write(kcode)
+        msg = self._get_device_msg()
+        if msg != _D2HMsgType.OBJECT_LOADED:
+            raise IOError("Incorrect reply from device: "+str(msg))
+
+    def run(self, kname):
+        self._write(struct.pack(
+            ">lbl", 0x5a5a5a5a, _H2DMsgType.RUN_KERNEL.value, len(kname)))
+        for c in kname:
+            self._write(struct.pack(">B", ord(c)))
+        logger.debug("running kernel: %s", kname)
+
+
+
+    def _receive_rpc_values(self):
+        r = []
+        while True:
+            type_tag = chr(struct.unpack(">B", self._read(1))[0])
+            if type_tag == "\x00":
+                return r
+            if type_tag == "n":
+                r.append(None)
+            if type_tag == "b":
+                r.append(bool(struct.unpack(">B", self._read(1))[0]))
+            if type_tag == "i":
+                r.append(struct.unpack(">l", self._read(4))[0])
+            if type_tag == "I":
+                r.append(struct.unpack(">q", self._read(8))[0])
+            if type_tag == "f":
+                r.append(struct.unpack(">d", self._read(8))[0])
+            if type_tag == "F":
+                n, d = struct.unpack(">qq", self._read(16))
+                r.append(Fraction(n, d))
+            if type_tag == "l":
+                r.append(self._receive_rpc_values())
+
+    def _serve_rpc(self, rpc_wrapper, rpc_map, user_exception_map):
+        rpc_num = struct.unpack(">h", self._read(2))[0]
+        args = self._receive_rpc_values()
+        logger.debug("rpc service: %d %r", rpc_num, args)
+        eid, r = rpc_wrapper.run_rpc(
+            user_exception_map, rpc_map[rpc_num], args)
+        self._write(struct.pack(">ll", eid, r))
+        logger.debug("rpc service: %d %r == %r", rpc_num, args, r)
+
+    def _serve_exception(self, rpc_wrapper, user_exception_map):
+        eid, p0, p1, p2 = struct.unpack(">lqqq", self._read(4+3*8))
+        rpc_wrapper.filter_rpc_exception(eid)
+        if eid < core_language.first_user_eid:
+            exception = runtime_exceptions.exception_map[eid]
+            raise exception(self.core, p0, p1, p2)
+        else:
+            exception = user_exception_map[eid]
+            raise exception
+
+    def serve(self, rpc_map, user_exception_map):
+        rpc_wrapper = RPCWrapper()
+        while True:
+            msg = self._get_device_msg()
+            if msg == _D2HMsgType.RPC_REQUEST:
+                self._serve_rpc(rpc_wrapper, rpc_map, user_exception_map)
+            elif msg == _D2HMsgType.KERNEL_EXCEPTION:
+                self._serve_exception(rpc_wrapper, user_exception_map)
+            elif msg == _D2HMsgType.KERNEL_FINISHED:
+                return
+            else:
+                raise IOError("Incorrect request from device: "+str(msg))
+
+    def send_link_message(self, data):
+        self._write(struct.pack(
+            ">lb", 0x5a5a5a5a, _H2DMsgType.LINK_MESSAGE.value))
+        self._write(data)
diff --git a/artiq/coredevice/comm_serial.py b/artiq/coredevice/comm_serial.py
index 322813297..b12cc03dd 100644
--- a/artiq/coredevice/comm_serial.py
+++ b/artiq/coredevice/comm_serial.py
@@ -1,89 +1,59 @@
+import logging
 import serial
 import struct
-import zlib
-from enum import Enum
-from fractions import Fraction
-import logging
 
-from artiq.language import core as core_language
-from artiq.language import units
+from artiq.coredevice.comm_generic import CommGeneric
 from artiq.language.db import *
-from artiq.coredevice.runtime import Environment
-from artiq.coredevice import runtime_exceptions
-from artiq.coredevice.rpc_wrapper import RPCWrapper
 
 
 logger = logging.getLogger(__name__)
 
 
-class UnsupportedDevice(Exception):
-    pass
-
-
-class _H2DMsgType(Enum):
-    REQUEST_IDENT = 1
-    LOAD_OBJECT = 2
-    RUN_KERNEL = 3
-    SET_BAUD_RATE = 4
-    SWITCH_CLOCK = 5
-
-
-class _D2HMsgType(Enum):
-    LOG = 1
-    MESSAGE_UNRECOGNIZED = 2
-    IDENT = 3
-    OBJECT_LOADED = 4
-    INCORRECT_LENGTH = 5
-    CRC_FAILED = 6
-    OBJECT_UNRECOGNIZED = 7
-    KERNEL_FINISHED = 8
-    KERNEL_EXCEPTION = 9
-    KERNEL_STARTUP_FAILED = 10
-    RPC_REQUEST = 11
-    CLOCK_SWITCH_COMPLETED = 12
-    CLOCK_SWITCH_FAILED = 13
-
-
-def _write_exactly(f, data):
-    remaining = len(data)
-    pos = 0
-    while remaining:
-        written = f.write(data[pos:])
-        remaining -= written
-        pos += written
-
-
-def _read_exactly(f, n):
-    r = bytes()
-    while(len(r) < n):
-        r += f.read(n - len(r))
-    return r
-
-
-class Comm(AutoDB):
+class Comm(CommGeneric, AutoDB):
     class DBKeys:
-        serial_dev = Parameter("/dev/ttyUSB1")
+        serial_dev = Parameter()
         baud_rate = Parameter(115200)
 
-    def build(self):
+    def open(self):
+        if hasattr(self, "port"):
+            return
         self.port = serial.serial_for_url(self.serial_dev, baudrate=115200)
         self.port.flush()
         self.set_remote_baud(self.baud_rate)
         self.set_baud(self.baud_rate)
-        self.rpc_wrapper = RPCWrapper()
+
+    def close(self):
+        if not hasattr(self, "port"):
+            return
+        self.set_remote_baud(115200)
+        self.port.close()
+        del self.port
+
+    def read(self, length):
+        r = bytes()
+        while(len(r) < length):
+            r += self.port.read(length - len(r))
+        return r
+
+    def write(self, data):
+        remaining = len(data)
+        pos = 0
+        while remaining:
+            written = self.port.write(data[pos:])
+            remaining -= written
+            pos += written
 
     def set_baud(self, baud):
         self.port.baudrate = baud
         self.port.flush()
-        logger.debug("baud rate set to %d", baud)
+        logger.debug("local baud rate set to %d", baud)
 
     def set_remote_baud(self, baud):
-        _write_exactly(self.port, struct.pack(
-            ">lbl", 0x5a5a5a5a, _H2DMsgType.SET_BAUD_RATE.value, baud))
+        self.send_link_message(struct.pack(">l", baud))
         handshake = 0
         fails = 0
         while handshake < 4:
-            (recv, ) = struct.unpack("B", _read_exactly(self.port, 1))
+            (recv, ) = struct.unpack("B", self.read(1))
             if recv == 0x5a:
                 handshake += 1
             else:
@@ -95,124 +65,4 @@ class Comm(AutoDB):
                     fails += 1
                     if fails > 3:
                         raise IOError("Baudrate ack failed")
-        self.set_baud(baud)
-        logger.debug("synchronized")
-
-    def close(self):
-        self.set_remote_baud(115200)
-        self.port.close()
-
-    def _get_device_msg(self):
-        while True:
-            (reply, ) = struct.unpack("B", _read_exactly(self.port, 1))
-            msg = _D2HMsgType(reply)
-            if msg == _D2HMsgType.LOG:
-                (length, ) = struct.unpack(">h", _read_exactly(self.port, 2))
-                log_message = ""
-                for i in range(length):
-                    (c, ) = struct.unpack("B", _read_exactly(self.port, 1))
-                    log_message += chr(c)
-                logger.info("DEVICE LOG: %s", log_message)
-            else:
-                logger.debug("message received: %r", msg)
-                return msg
-
-    def get_runtime_env(self):
-        _write_exactly(self.port, struct.pack(
-            ">lb", 0x5a5a5a5a, _H2DMsgType.REQUEST_IDENT.value))
-        msg = self._get_device_msg()
-        if msg != _D2HMsgType.IDENT:
-            raise IOError("Incorrect reply from device: "+str(msg))
-        (reply, ) = struct.unpack("B", _read_exactly(self.port, 1))
-        runtime_id = chr(reply)
-        for i in range(3):
-            (reply, ) = struct.unpack("B", _read_exactly(self.port, 1))
-            runtime_id += chr(reply)
-        if runtime_id != "AROR":
-            raise UnsupportedDevice("Unsupported runtime ID: "+runtime_id)
-        ref_freq_i, ref_freq_fn, ref_freq_fd = struct.unpack(
-            ">lBB", _read_exactly(self.port, 6))
-        ref_freq = (ref_freq_i + Fraction(ref_freq_fn, ref_freq_fd))*units.Hz
-        ref_period = 1/ref_freq
-        logger.debug("environment ref_period: %s", ref_period)
-        return Environment(ref_period)
-
-    def switch_clock(self, external):
-        _write_exactly(self.port, struct.pack(
-            ">lbb", 0x5a5a5a5a, _H2DMsgType.SWITCH_CLOCK.value,
-            int(external)))
-        msg = self._get_device_msg()
-        if msg != _D2HMsgType.CLOCK_SWITCH_COMPLETED:
-            raise IOError("Incorrect reply from device: "+str(msg))
-
-    def load(self, kcode):
-        _write_exactly(self.port, struct.pack(
-            ">lblL",
-            0x5a5a5a5a, _H2DMsgType.LOAD_OBJECT.value,
-            len(kcode), zlib.crc32(kcode)))
-        _write_exactly(self.port, kcode)
-        msg = self._get_device_msg()
-        if msg != _D2HMsgType.OBJECT_LOADED:
-            raise IOError("Incorrect reply from device: "+str(msg))
-
-    def run(self, kname):
-        _write_exactly(self.port, struct.pack(
-            ">lbl", 0x5a5a5a5a, _H2DMsgType.RUN_KERNEL.value, len(kname)))
-        for c in kname:
-            _write_exactly(self.port, struct.pack(">B", ord(c)))
-        logger.debug("running kernel: %s", kname)
-
-    def _receive_rpc_values(self):
-        r = []
-        while True:
-            type_tag = chr(struct.unpack(">B", _read_exactly(self.port, 1))[0])
-            if type_tag == "\x00":
-                return r
-            if type_tag == "n":
-                r.append(None)
-            if type_tag == "b":
-                r.append(bool(struct.unpack(">B",
-                                            _read_exactly(self.port, 1))[0]))
-            if type_tag == "i":
-                r.append(struct.unpack(">l", _read_exactly(self.port, 4))[0])
-            if type_tag == "I":
-                r.append(struct.unpack(">q", _read_exactly(self.port, 8))[0])
-            if type_tag == "f":
-                r.append(struct.unpack(">d", _read_exactly(self.port, 8))[0])
-            if type_tag == "F":
-                n, d = struct.unpack(">qq", _read_exactly(self.port, 16))
-                r.append(Fraction(n, d))
-            if type_tag == "l":
-                r.append(self._receive_rpc_values())
-
-    def _serve_rpc(self, rpc_map, user_exception_map):
-        rpc_num = struct.unpack(">h", _read_exactly(self.port, 2))[0]
-        args = self._receive_rpc_values()
-        logger.debug("rpc service: %d %r", rpc_num, args)
-        eid, r = self.rpc_wrapper.run_rpc(
-            user_exception_map, rpc_map[rpc_num], args)
-        _write_exactly(self.port, struct.pack(">ll", eid, r))
-        logger.debug("rpc service: %d %r == %r", rpc_num, args, r)
-
-    def _serve_exception(self, user_exception_map):
-        eid, p0, p1, p2 = struct.unpack(">lqqq",
-                                        _read_exactly(self.port, 4+3*8))
-        self.rpc_wrapper.filter_rpc_exception(eid)
-        if eid < core_language.first_user_eid:
-            exception = runtime_exceptions.exception_map[eid]
-            raise exception(self.core, p0, p1, p2)
-        else:
-            exception = user_exception_map[eid]
-            raise exception
-
-    def serve(self, rpc_map, user_exception_map):
-        while True:
-            msg = self._get_device_msg()
-            if msg == _D2HMsgType.RPC_REQUEST:
-                self._serve_rpc(rpc_map, user_exception_map)
-            elif msg == _D2HMsgType.KERNEL_EXCEPTION:
-                self._serve_exception(user_exception_map)
-            elif msg == _D2HMsgType.KERNEL_FINISHED:
-                return
-            else:
-                raise IOError("Incorrect request from device: "+str(msg))
+        logger.debug("remote baud rate set to %d", baud)
diff --git a/soc/runtime/comm_serial.c b/soc/runtime/comm_serial.c
index 77bbcce95..fc4c7d841 100644
--- a/soc/runtime/comm_serial.c
+++ b/soc/runtime/comm_serial.c
@@ -12,33 +12,34 @@
 
 /* host to device */
 enum {
-    MSGTYPE_REQUEST_IDENT = 1,
+    MSGTYPE_SET_BAUD_RATE = 1,
+
+    MSGTYPE_REQUEST_IDENT,
+    MSGTYPE_SWITCH_CLOCK,
+    
     MSGTYPE_LOAD_OBJECT,
     MSGTYPE_RUN_KERNEL,
-    MSGTYPE_SET_BAUD_RATE,
-    MSGTYPE_SWITCH_CLOCK,
 };
 
 /* device to host */
 enum {
-    MSGTYPE_LOG = 1,
-    MSGTYPE_MESSAGE_UNRECOGNIZED,
+    MSGTYPE_MESSAGE_UNRECOGNIZED = 1,
+    MSGTYPE_LOG,
 
     MSGTYPE_IDENT,
+    MSGTYPE_CLOCK_SWITCH_COMPLETED,
+    MSGTYPE_CLOCK_SWITCH_FAILED,
 
     MSGTYPE_OBJECT_LOADED,
-    MSGTYPE_INCORRECT_LENGTH,
-    MSGTYPE_CRC_FAILED,
+    MSGTYPE_OBJECT_INCORRECT_LENGTH,
+    MSGTYPE_OBJECT_CRC_FAILED,
     MSGTYPE_OBJECT_UNRECOGNIZED,
 
     MSGTYPE_KERNEL_FINISHED,
-    MSGTYPE_KERNEL_EXCEPTION,
     MSGTYPE_KERNEL_STARTUP_FAILED,
+    MSGTYPE_KERNEL_EXCEPTION,
 
     MSGTYPE_RPC_REQUEST,
-
-    MSGTYPE_CLOCK_SWITCH_COMPLETED,
-    MSGTYPE_CLOCK_SWITCH_FAILED,
 };
 
 static int receive_int(void)
@@ -114,14 +115,14 @@ static void receive_and_load_object(object_loader load_object)
 
     length = receive_int();
     if(length > sizeof(buffer)) {
-        send_char(MSGTYPE_INCORRECT_LENGTH);
+        send_char(MSGTYPE_OBJECT_INCORRECT_LENGTH);
         return;
     }
     crc = receive_int();
     for(i=0;i<length;i++)
         buffer[i] = receive_char();
     if(crc32(buffer, length) != crc) {
-        send_char(MSGTYPE_CRC_FAILED);
+        send_char(MSGTYPE_OBJECT_CRC_FAILED);
         return;
     }
     if(load_object(buffer, length))
@@ -140,7 +141,7 @@ static void receive_and_run_kernel(kernel_runner run_kernel)
 
     length = receive_int();
     if(length > (sizeof(kernel_name)-1)) {
-        send_char(MSGTYPE_INCORRECT_LENGTH);
+        send_char(MSGTYPE_OBJECT_INCORRECT_LENGTH);
         return;
     }
     for(i=0;i<length;i++)