vxi11.py

"""

Python VXI-11 driver

Copyright (c) 2012-2017 Alex Forencich and Michael Walle

Permission is hereby granted, free of charge, to any person obtaining a copy
of this software and associated documentation files (the "Software"), to deal
in the Software without restriction, including without limitation the rights
to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
copies of the Software, and to permit persons to whom the Software is
furnished to do so, subject to the following conditions:

The above copyright notice and this permission notice shall be included in
all copies or substantial portions of the Software.

THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY
FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
THE SOFTWARE.

"""

from . import rpc
import random
import re
import struct
import time

# VXI-11 RPC constants

# Device async
DEVICE_ASYNC_PROG = 0x0607b0
DEVICE_ASYNC_VERS = 1
DEVICE_ABORT      = 1

# Device core
DEVICE_CORE_PROG  = 0x0607af
DEVICE_CORE_VERS  = 1
CREATE_LINK       = 10
DEVICE_WRITE      = 11
DEVICE_READ       = 12
DEVICE_READSTB    = 13
DEVICE_TRIGGER    = 14
DEVICE_CLEAR      = 15
DEVICE_REMOTE     = 16
DEVICE_LOCAL      = 17
DEVICE_LOCK       = 18
DEVICE_UNLOCK     = 19
DEVICE_ENABLE_SRQ = 20
DEVICE_DOCMD      = 22
DESTROY_LINK      = 23
CREATE_INTR_CHAN  = 25
DESTROY_INTR_CHAN = 26

# Device intr
DEVICE_INTR_PROG  = 0x0607b1
DEVICE_INTR_VERS  = 1
DEVICE_INTR_SRQ   = 30

# Error states
ERR_NO_ERROR = 0
ERR_SYNTAX_ERROR = 1
ERR_DEVICE_NOT_ACCESSIBLE = 3
ERR_INVALID_LINK_IDENTIFIER = 4
ERR_PARAMETER_ERROR = 5
ERR_CHANNEL_NOT_ESTABLISHED = 6
ERR_OPERATION_NOT_SUPPORTED = 8
ERR_OUT_OF_RESOURCES = 9
ERR_DEVICE_LOCKED_BY_ANOTHER_LINK = 11
ERR_NO_LOCK_HELD_BY_THIS_LINK = 12
ERR_IO_TIMEOUT = 15
ERR_IO_ERROR = 17
ERR_INVALID_ADDRESS = 21
ERR_ABORT = 23
ERR_CHANNEL_ALREADY_ESTABLISHED = 29

# Flags
OP_FLAG_WAIT_BLOCK = 1
OP_FLAG_END = 8
OP_FLAG_TERMCHAR_SET = 128

RX_REQCNT = 1
RX_CHR = 2
RX_END = 4

# IEEE 488.1 interface device commands
CMD_SEND_COMMAND = 0x020000
CMD_BUS_STATUS   = 0x020001
CMD_ATN_CTRL     = 0x020002
CMD_REN_CTRL     = 0x020003
CMD_PASS_CTRL    = 0x020004
CMD_BUS_ADDRESS  = 0x02000A
CMD_IFC_CTRL     = 0x020010

CMD_BUS_STATUS_REMOTE = 1
CMD_BUS_STATUS_SRQ = 2
CMD_BUS_STATUS_NDAC = 3
CMD_BUS_STATUS_SYSTEM_CONTROLLER = 4
CMD_BUS_STATUS_CONTROLLER_IN_CHARGE = 5
CMD_BUS_STATUS_TALKER = 6
CMD_BUS_STATUS_LISTENER = 7
CMD_BUS_STATUS_BUS_ADDRESS = 8

GPIB_CMD_GTL = 0x01 # go to local
GPIB_CMD_SDC = 0x04 # selected device clear
GPIB_CMD_PPC = 0x05 # parallel poll config
GPIB_CMD_GET = 0x08 # group execute trigger
GPIB_CMD_TCT = 0x09 # take control
GPIB_CMD_LLO = 0x11 # local lockout
GPIB_CMD_DCL = 0x14 # device clear
GPIB_CMD_PPU = 0x15 # parallel poll unconfigure
GPIB_CMD_SPE = 0x18 # serial poll enable
GPIB_CMD_SPD = 0x19 # serial poll disable
GPIB_CMD_LAD = 0x20 # listen address (base)
GPIB_CMD_UNL = 0x3F # unlisten
GPIB_CMD_TAD = 0x40 # talk address (base)
GPIB_CMD_UNT = 0x5F # untalk
GPIB_CMD_SAD = 0x60 # my secondary address (base)
GPIB_CMD_PPE = 0x60 # parallel poll enable (base)
GPIB_CMD_PPD = 0x70 # parallel poll disable

def parse_visa_resource_string(resource_string):
    # valid resource strings:
    # TCPIP::10.0.0.1::INSTR
    # TCPIP0::10.0.0.1::INSTR
    # TCPIP::10.0.0.1::gpib,5::INSTR
    # TCPIP0::10.0.0.1::gpib,5::INSTR
    # TCPIP0::10.0.0.1::usb0::INSTR
    # TCPIP0::10.0.0.1::usb0[1234::5678::MYSERIAL::0]::INSTR
    m = re.match('^(?P<prefix>(?P<type>TCPIP)\d*)(::(?P<arg1>[^\s:]+))'
            '(::(?P<arg2>[^\s:]+(\[.+\])?))?(::(?P<suffix>INSTR))$',
            resource_string, re.I)

    if m is not None:
        return dict(
                type = m.group('type').upper(),
                prefix = m.group('prefix'),
                arg1 = m.group('arg1'),
                arg2 = m.group('arg2'),
                suffix = m.group('suffix'),
        )

# Exceptions
class Vxi11Exception(Exception):
    em = {0:  "No error",
          1:  "Syntax error",
          3:  "Device not accessible",
          4:  "Invalid link identifier",
          5:  "Parameter error",
          6:  "Channel not established",
          8:  "Operation not supported",
          9:  "Out of resources",
          11: "Device locked by another link",
          12: "No lock held by this link",
          15: "IO timeout",
          17: "IO error",
          21: "Invalid address",
          23: "Abort",
          29: "Channel already established"}

    def __init__(self, err = None, note = None):
        self.err = err
        self.note = note
        self.msg = ''

        if err is None:
            self.msg = note
        else:
            if type(err) is int:
                if err in self.em:
                    self.msg = "%d: %s" % (err, self.em[err])
                else:
                    self.msg = "%d: Unknown error" % err
            else:
                self.msg = err
            if note is not None:
                self.msg = "%s [%s]" % (self.msg, note)

    def __str__(self):
        return self.msg

class Packer(rpc.Packer):
    def pack_device_link(self, link):
        self.pack_int(link)

    def pack_create_link_parms(self, params):
        id, lock_device, lock_timeout, device = params
        self.pack_int(id)
        self.pack_bool(lock_device)
        self.pack_uint(lock_timeout)
        self.pack_string(device)

    def pack_device_write_parms(self, params):
        link, timeout, lock_timeout, flags, data = params
        self.pack_int(link)
        self.pack_uint(timeout)
        self.pack_uint(lock_timeout)
        self.pack_int(flags)
        self.pack_opaque(data)

    def pack_device_read_parms(self, params):
        link, request_size, timeout, lock_timeout, flags, term_char = params
        self.pack_int(link)
        self.pack_uint(request_size)
        self.pack_uint(timeout)
        self.pack_uint(lock_timeout)
        self.pack_int(flags)
        self.pack_int(term_char)

    def pack_device_generic_parms(self, params):
        link, flags, lock_timeout, timeout = params
        self.pack_int(link)
        self.pack_int(flags)
        self.pack_uint(lock_timeout)
        self.pack_uint(timeout)

    def pack_device_remote_func_parms(self, params):
        host_addr, host_port, prog_num, prog_vers, prog_family = params
        self.pack_uint(host_addr)
        self.pack_uint(host_port)
        self.pack_uint(prog_num)
        self.pack_uint(prog_vers)
        self.pack_int(prog_family)

    def pack_device_enable_srq_parms(self, params):
        link, enable, handle = params
        self.pack_int(link)
        self.pack_bool(enable)
        if len(handle) > 40:
            raise Vxi11Exception("array length too long")
        self.pack_opaque(handle)

    def pack_device_lock_parms(self, params):
        link, flags, lock_timeout = params
        self.pack_int(link)
        self.pack_int(flags)
        self.pack_uint(lock_timeout)

    def pack_device_docmd_parms(self, params):
        link, flags, timeout, lock_timeout, cmd, network_order, datasize, data_in = params
        self.pack_int(link)
        self.pack_int(flags)
        self.pack_uint(timeout)
        self.pack_uint(lock_timeout)
        self.pack_int(cmd)
        self.pack_bool(network_order)
        self.pack_int(datasize)
        self.pack_opaque(data_in)

    def pack_device_error(self, error):
        self.pack_int(error)

    def pack_device_srq_parms(self, params):
        handle = params
        self.pack_opaque(handle)

    def pack_create_link_resp(self, params):
        error, link, abort_port, max_recv_size = params
        self.pack_int(error)
        self.pack_int(link)
        self.pack_uint(abort_port)
        self.pack_uint(max_recv_size)

    def pack_device_write_resp(self, params):
        error, size = params
        self.pack_int(error)
        self.pack_uint(size)

    def pack_device_read_resp(self, params):
        error, reason, data = params
        self.pack_int(error)
        self.pack_int(reason)
        self.pack_opaque(data)

    def pack_device_read_stb_resp(self, params):
        error, stb = params
        self.pack_int(error)
        self.pack_uint(stb)

    def pack_device_docmd_resp(self, params):
        error, data_out = params
        self.pack_int(error)
        self.pack_opaque(data_out)

class Unpacker(rpc.Unpacker):
    def unpack_device_link(self):
        return self.unpack_int()

    def unpack_create_link_parms(self):
        id = self.unpack_int()
        lock_device = self.unpack_bool()
        lock_timeout = self.unpack_uint()
        device = self.unpack_string()
        return id, lock_device, lock_timeout, device

    def unpack_device_write_parms(self):
        link = self.unpack_int()
        timeout = self.unpack_uint()
        lock_timeout = self.unpack_uint()
        flags = self.unpack_int()
        data = self.unpack_opaque()
        return link, timeout, lock_timeout, flags, data

    def unpack_device_read_parms(self):
        link = self.unpack_int()
        request_size = self.unpack_uint()
        timeout = self.unpack_uint()
        lock_timeout = self.unpack_uint()
        flags = self.unpack_int()
        term_char = self.unpack_int()
        return link, request_size, timeout, lock_timeout, flags, term_char

    def unpack_device_generic_parms(self):
        link = self.unpack_int()
        flags = self.unpack_int()
        lock_timeout = self.unpack_uint()
        timeout = self.unpack_uint()
        return link, flags, lock_timeout, timeout

    def unpack_device_remote_func_parms(self):
        host_addr = self.unpack_uint()
        host_port = self.unpack_uint()
        prog_num = self.unpack_uint()
        prog_vers = self.unpack_uint()
        prog_family = self.unpack_int()
        return host_addr, host_port, prog_num, prog_vers, prog_family

    def unpack_device_enable_srq_parms(self):
        link = self.unpack_int()
        enable = self.unpack_bool()
        handle = self.unpack_opaque()
        return link, enable, handle

    def unpack_device_lock_parms(self):
        link = self.unpack_int()
        flags = self.unpack_int()
        lock_timeout = self.unpack_uint()
        return link, flags, lock_timeout

    def unpack_device_docmd_parms(self):
        link = self.unpack_int()
        flags = self.unpack_int()
        timeout = self.unpack_uint()
        lock_timeout = self.unpack_uint()
        cmd = self.unpack_int()
        network_order = self.unpack_bool()
        datasize = self.unpack_int()
        data_in = self.unpack_opaque()
        return link, flags, timeout, lock_timeout, cmd, network_order, datasize, data_in

    def unpack_device_error(self):
        return self.unpack_int()

    def unpack_device_srq_params(self):
        handle = self.unpack_opaque()
        return handle

    def unpack_create_link_resp(self):
        error = self.unpack_int()
        link = self.unpack_int()
        abort_port = self.unpack_uint()
        max_recv_size = self.unpack_uint()
        return error, link, abort_port, max_recv_size

    def unpack_device_write_resp(self):
        error = self.unpack_int()
        size = self.unpack_uint()
        return error, size

    def unpack_device_read_resp(self):
        error = self.unpack_int()
        reason = self.unpack_int()
        data = self.unpack_opaque()
        return error, reason, data

    def unpack_device_read_stb_resp(self):
        error = self.unpack_int()
        stb = self.unpack_uint()
        return error, stb

    def unpack_device_docmd_resp(self):
        error = self.unpack_int()
        data_out = self.unpack_opaque()
        return error, data_out

    def done(self):
        # ignore any trailing bytes
        pass


class CoreClient(rpc.TCPClient):
    def __init__(self, host, tcp_quickack, port=0):
        self.packer = Packer()
        self.unpacker = Unpacker('')
        rpc.TCPClient.__init__(self, host, DEVICE_CORE_PROG, DEVICE_CORE_VERS, tcp_quickack, port)

    def create_link(self, id, lock_device, lock_timeout, name):
        params = (id, lock_device, lock_timeout, name)
        return self.make_call(CREATE_LINK, params,
                self.packer.pack_create_link_parms,
                self.unpacker.unpack_create_link_resp)

    def device_write(self, link, timeout, lock_timeout, flags, data):
        params = (link, timeout, lock_timeout, flags, data)
        return self.make_call(DEVICE_WRITE, params,
                self.packer.pack_device_write_parms,
                self.unpacker.unpack_device_write_resp)

    def device_read(self, link, request_size, timeout, lock_timeout, flags, term_char):
        params = (link, request_size, timeout, lock_timeout, flags, term_char)
        return self.make_call(DEVICE_READ, params,
                self.packer.pack_device_read_parms,
                self.unpacker.unpack_device_read_resp)

    def device_read_stb(self, link, flags, lock_timeout, timeout):
        params = (link, flags, lock_timeout, timeout)
        return self.make_call(DEVICE_READSTB, params,
                self.packer.pack_device_generic_parms,
                self.unpacker.unpack_device_read_stb_resp)

    def device_trigger(self, link, flags, lock_timeout, timeout):
        params = (link, flags, lock_timeout, timeout)
        return self.make_call(DEVICE_TRIGGER, params,
                self.packer.pack_device_generic_parms,
                self.unpacker.unpack_device_error)

    def device_clear(self, link, flags, lock_timeout, timeout):
        params = (link, flags, lock_timeout, timeout)
        return self.make_call(DEVICE_CLEAR, params,
                self.packer.pack_device_generic_parms,
                self.unpacker.unpack_device_error)

    def device_remote(self, link, flags, lock_timeout, timeout):
        params = (link, flags, lock_timeout, timeout)
        return self.make_call(DEVICE_REMOTE, params,
                self.packer.pack_device_generic_parms,
                self.unpacker.unpack_device_error)

    def device_local(self, link, flags, lock_timeout, timeout):
        params = (link, flags, lock_timeout, timeout)
        return self.make_call(DEVICE_LOCAL, params,
                self.packer.pack_device_generic_parms,
                self.unpacker.unpack_device_error)

    def device_lock(self, link, flags, lock_timeout):
        params = (link, flags, lock_timeout)
        return self.make_call(DEVICE_LOCK, params,
                self.packer.pack_device_lock_parms,
                self.unpacker.unpack_device_error)

    def device_unlock(self, link):
        return self.make_call(DEVICE_UNLOCK, link,
                self.packer.pack_device_link,
                self.unpacker.unpack_device_error)

    def device_enable_srq(self, link, enable, handle):
        params = (link, enable, handle)
        return self.make_call(DEVICE_ENABLE_SRQ, params,
                self.packer.pack_device_enable_srq_parms,
                self.unpacker.unpack_device_error)

    def device_docmd(self, link, flags, timeout, lock_timeout, cmd, network_order, datasize, data_in):
        params = (link, flags, timeout, lock_timeout, cmd, network_order, datasize, data_in)
        return self.make_call(DEVICE_DOCMD, params,
                self.packer.pack_device_docmd_parms,
                self.unpacker.unpack_device_docmd_resp)

    def destroy_link(self, link):
        return self.make_call(DESTROY_LINK, link,
                self.packer.pack_device_link,
                self.unpacker.unpack_device_error)

    def create_intr_chan(self, host_addr, host_port, prog_num, prog_vers, prog_family):
        params = (host_addr, host_port, prog_num, prog_vers, prog_family)
        return self.make_call(CREATE_INTR_CHAN, params,
                self.packer.pack_device_remote_func_parms,
                self.unpacker.unpack_device_error)

    def destroy_intr_chan(self):
        return self.make_call(DESTROY_INTR_CHAN, None,
                None,
                self.unpacker.unpack_device_error)


class AbortClient(rpc.TCPClient):
    def __init__(self, host, port=0):
        self.packer = Packer()
        self.unpacker = Unpacker('')
        rpc.TCPClient.__init__(self, host, DEVICE_ASYNC_PROG, DEVICE_ASYNC_VERS, port)

    def device_abort(self, link):
        return self.make_call(DEVICE_ABORT, link,
                self.packer.pack_device_link,
                self.unpacker.unpack_device_error)


def list_devices(ip=None, timeout=1):
    "Detect VXI-11 devices on network"

    if ip is None:
        ip = ['255.255.255.255']

    if type(ip) is str:
        ip = [ip]

    hosts = []

    for addr in ip:
        pmap = rpc.BroadcastUDPPortMapperClient(addr)
        pmap.set_timeout(timeout)
        resp = pmap.get_port((DEVICE_CORE_PROG, DEVICE_CORE_VERS, rpc.IPPROTO_TCP, 0))

        l = [r[1][0] for r in resp if r[0] > 0]

        hosts.extend(l)

    return sorted(hosts, key=lambda ip: tuple(int(part) for part in ip.split('.')))


def list_resources(ip=None, timeout=1):
    "List resource strings for all detected VXI-11 devices"

    res = []

    for host in list_devices(ip, timeout):
        try:
            # try connecting as an instrument
            instr = Instrument(host)
            instr.open()
            res.append("TCPIP::%s::INSTR" % host)
        except:
            try:
                # try connecting as a GPIB interface
                intf_dev = InterfaceDevice(host)
                # enumerate connected devices
                devs = intf_dev.find_listeners()
                res.extend(['TCPIP::%s::gpib0,%d::INSTR' % (host, d) for d in devs])
            except:
                # if that fails, just list the host
                res.append("TCPIP::%s::INSTR" % host)

    return res


class Device(object):
    "VXI-11 device interface client"
    def __init__(self, host, name = None, client_id = None, term_char = None):
        "Create new VXI-11 device object"

        if host.upper().startswith('TCPIP') and '::' in host:
            res = parse_visa_resource_string(host)

            if res is None:
                raise Vxi11Exception('Invalid resource string', 'init')

            host = res['arg1']
            name = res['arg2']

        if name is None:
            name = "inst0"

        if client_id is None:
            client_id = random.getrandbits(31)

        self.client = None
        self.abort_client = None

        self.host = host
        self.name = name
        self.client_id = client_id
        self.term_char = term_char
        self.lock_timeout = 10
        self._tcp_quickack = 1
        self.timeout = 10
        self.abort_port = 0
        self.link = None
        self.max_recv_size = 0
        self.max_read_len = 128*1024*1024
        self.locked = False

    def __del__(self):
        if self.link is not None:
            self.close()

    @property
    def timeout(self):
        return self._timeout

    @timeout.setter
    def timeout(self, val):
        self._timeout = val
        self._timeout_ms = int(val * 1000)
        if self.client is not None:
            self.client.sock.settimeout(self.timeout+1)
        if self.abort_client is not None:
            self.abort_client.sock.settimeout(self.timeout+1)

    @property
    def lock_timeout(self):
        return self._lock_timeout

    @lock_timeout.setter
    def lock_timeout(self, val):
        self._lock_timeout = val
        self._lock_timeout_ms = int(val * 1000)

    @property
    def tcp_quickack(self):
        return self._tcp_quickack

    def enable_tcp_quickack(self):
        #Enable Socket TCP_QUICKACK. This is enabled by default in the socket class.
        #Should be enabled/disabled before open()
        if self.client is None:
            self._tcp_quickack = 1
        else:
            raise Vxi11Exception("client already oppened! Use it before open the connection!")
        
    def disable_tcp_quickack(self):
        #Disable Socket TCP_QUICKACK. This should be disabled if your connection is
        #having a lot of double acks and retransmissions. Should be enabled/disabled before open()
        #This does nothing for Windows OS
        if self.client is None:
            self._tcp_quickack = 0
        else:
            raise Vxi11Exception("client already oppened! Use it before open the connection!")
        
    def open(self):
        "Open connection to VXI-11 device"
        if self.link is not None:
            return

        if self.client is None:
            self.client = CoreClient(self.host, self.tcp_quickack)

        self.client.sock.settimeout(self.timeout+1)
        error, link, abort_port, max_recv_size = self.client.create_link(
            self.client_id,
            0,
            self._lock_timeout_ms,
            self.name.encode("utf-8")
        )

        if error:
            raise Vxi11Exception(error, 'open')

        self.abort_port = abort_port

        self.link = link
        self.max_recv_size = min(max_recv_size, 1024*1024)

    def close(self):
        "Close connection"
        if self.link is None:
            return

        self.client.destroy_link(self.link)
        self.client.close()
        self.link = None
        self.client = None

    def abort(self):
        "Asynchronous abort"
        if self.link is None:
            self.open()

        if self.abort_client is None:
            self.abort_client = AbortClient(self.host, self.abort_port)
            self.abort_client.sock.settimeout(self.timeout)

        error = self.abort_client.device_abort(self.link)

        if error:
            raise Vxi11Exception(error, 'abort')

    def write_raw(self, data):
        "Write binary data to instrument"
        if self.link is None:
            self.open()

        if self.term_char is not None:
            flags = OP_FLAG_TERMCHAR_SET
            term_char = str(self.term_char).encode('utf-8')[0]
            data += term_char

        flags = 0

        num = len(data)

        offset = 0

        while num > 0:
            if num <= self.max_recv_size:
                flags |= OP_FLAG_END

            block = data[offset:offset+self.max_recv_size]

            error, size = self.client.device_write(
                self.link,
                self._timeout_ms,
                self._lock_timeout_ms,
                flags,
                block
            )

            if error:
                raise Vxi11Exception(error, 'write')
            elif size < len(block):
                raise Vxi11Exception("did not write complete block", 'write')

            offset += size
            num -= size

    def read_raw(self, num=-1):
        "Read binary data from instrument"
        if self.link is None:
            self.open()

        read_len = self.max_read_len
        if num > 0:
            read_len = min(num, self.max_read_len)

        flags = 0
        reason = 0

        term_char = 0

        if self.term_char is not None:
            flags = OP_FLAG_TERMCHAR_SET
            term_char = str(self.term_char).encode('utf-8')[0]

        read_data = bytearray()

        while reason & (RX_END | RX_CHR) == 0:
            error, reason, data = self.client.device_read(
                self.link,
                read_len,
                self._timeout_ms,
                self._lock_timeout_ms,
                flags,
                term_char
            )

            if error:
                raise Vxi11Exception(error, 'read')

            read_data.extend(data)

            if num > 0:
                num = num - len(data)
                if num <= 0:
                    break
                if num < read_len:
                    read_len = num

        return bytes(read_data)

    def ask_raw(self, data, num=-1):
        "Write then read binary data"
        self.write_raw(data)
        return self.read_raw(num)

    def write(self, message, encoding = 'utf-8'):
        "Write string to instrument"
        if type(message) is tuple or type(message) is list:
            # recursive call for a list of commands
            for message_i in message:
                self.write(message_i, encoding)
            return

        self.write_raw(str(message).encode(encoding))

    def read(self, num=-1, encoding = 'utf-8'):
        "Read string from instrument"
        return self.read_raw(num).decode(encoding).rstrip('\r\n')

    def ask(self, message, num=-1, encoding = 'utf-8'):
        "Write then read string"
        if type(message) is tuple or type(message) is list:
            # recursive call for a list of commands
            val = list()
            for message_i in message:
                val.append(self.ask(message_i, num, encoding))
            return val

        self.write(message, encoding)
        return self.read(num, encoding)

    def trigger(self):
        "Send trigger command"
        if self.link is None:
            self.open()

        flags = 0

        error = self.client.device_trigger(
            self.link,
            flags,
            self._lock_timeout_ms,
            self._timeout_ms
        )

        if error:
            raise Vxi11Exception(error, 'trigger')

    def clear(self):
        "Send clear command"
        if self.link is None:
            self.open()

        flags = 0

        error = self.client.device_clear(
            self.link,
            flags,
            self._lock_timeout_ms,
            self._timeout_ms
        )

        if error:
            raise Vxi11Exception(error, 'clear')

    def lock(self):
        "Send lock command"
        if self.link is None:
            self.open()

        flags = 0

        error = self.client.device_lock(
            self.link,
            flags,
            self._lock_timeout_ms
        )

        if error:
            raise Vxi11Exception(error, 'lock')

        self.locked = True

    def unlock(self):
        "Send unlock command"
        if self.link is None:
            self.open()

        flags = 0

        error = self.client.device_unlock(self.link)

        if error:
            raise Vxi11Exception(error, 'unlock')

        self.locked = False


class InterfaceDevice(Device):
    "VXI-11 IEEE 488.1 interface device interface client"
    def __init__(self, host, name = None, client_id = None, term_char = None):
        "Create new VXI-11 488.1 interface device object"

        if host.upper().startswith('TCPIP') and '::' in host:
            res = parse_visa_resource_string(host)

            if res is None:
                raise Vxi11Exception('Invalid resource string', 'init')

            host = res['arg1']
            name = res['arg2']

        if name is None:
            name = "gpib0"

        super(InterfaceDevice, self).__init__(host, name, client_id, term_char)

        self._bus_address = 0

    def open(self):
        "Open connection to VXI-11 device"
        if self.link is not None:
            return

        if ',' in self.name:
            raise Vxi11Exception("Cannot specify address for InterfaceDevice")

        super(InterfaceDevice, self).open()

        self._bus_address = self.get_bus_address()

    def send_command(self, data):
        "Send command"
        if self.link is None:
            self.open()

        flags = 0

        error, data_out = self.client.device_docmd(
            self.link,
            flags,
            self._timeout_ms,
            self._lock_timeout_ms,
            CMD_SEND_COMMAND,
            True,
            1,
            data
        )

        if error:
            raise Vxi11Exception(error, 'send_command')

        return data_out

    def create_setup(self, address_list):
        data = bytearray([self._bus_address | GPIB_CMD_TAD, GPIB_CMD_UNL])

        if type(address_list) is int:
            address_list = [address_list]

        for addr in address_list:
            if type(addr) is tuple:
                if addr[0] < 0 or addr[0] > 30:
                    raise Vxi11Exception("Invalid address", 'create_setup')
                data.append(addr[0] | GPIB_CMD_LAD)
                if len(addr) > 1:
                    if addr[1] < 0 or addr[1] > 30:
                        raise Vxi11Exception("Invalid address", 'create_setup')
                    data.append(addr[1] | GPIB_CMD_SAD)
            else:
                if addr < 0 or addr > 30:
                    raise Vxi11Exception("Invalid address", 'create_setup')
                data.append(addr | GPIB_CMD_LAD)

        return bytes(data)

    def send_setup(self, address_list):
        "Send setup"
        return self.send_command(self.create_setup(address_list))

    def _bus_status(self, val):
        "Bus status"
        if self.link is None:
            self.open()

        flags = 0

        error, data_out = self.client.device_docmd(
            self.link,
            flags,
            self._timeout_ms,
            self._lock_timeout_ms,
            CMD_BUS_STATUS,
            True,
            2,
            struct.pack('!H', val)
        )

        if error:
            raise Vxi11Exception(error, 'bus_status')

        return struct.unpack('!H', data_out)[0]

    def test_ren(self):
        "Read REN line"
        return self._bus_status(CMD_BUS_STATUS_REMOTE)

    def test_srq(self):
        "Read SRQ line"
        return self._bus_status(CMD_BUS_STATUS_SRQ)

    def test_ndac(self):
        "Read NDAC line"
        return self._bus_status(CMD_BUS_STATUS_NDAC)

    def is_system_controller(self):
        "Check if interface device is a system controller"
        return self._bus_status(CMD_BUS_STATUS_SYSTEM_CONTROLLER)

    def is_controller_in_charge(self):
        "Check if interface device is the controller-in-charge"
        return self._bus_status(CMD_BUS_STATUS_CONTROLLER_IN_CHARGE)

    def is_talker(self):
        "Check if interface device is addressed as a talker"
        return self._bus_status(CMD_BUS_STATUS_TALKER)

    def is_listener(self):
        "Check if interface device is addressed as a listener"
        return self._bus_status(CMD_BUS_STATUS_LISTENER)

    def get_bus_address(self):
        "Get interface device bus address"
        return self._bus_status(CMD_BUS_STATUS_BUS_ADDRESS)

    def set_atn(self, val):
        "Set ATN line"
        if self.link is None:
            self.open()

        flags = 0

        error, data_out = self.client.device_docmd(
            self.link,
            flags,
            self._timeout_ms,
            self._lock_timeout_ms,
            CMD_ATN_CTRL,
            True,
            2,
            struct.pack('!H', val)
        )

        if error:
            raise Vxi11Exception(error, 'set_atn')

        return struct.unpack('!H', data_out)[0]

    def set_ren(self, val):
        "Set REN line"
        if self.link is None:
            self.open()

        flags = 0

        error, data_out = self.client.device_docmd(
            self.link,
            flags,
            self._timeout_ms,
            self._lock_timeout_ms,
            CMD_REN_CTRL,
            True,
            2,
            struct.pack('!H', val)
        )

        if error:
            raise Vxi11Exception(error, 'set_ren')

        return struct.unpack('!H', data_out)[0]

    def pass_control(self, addr):
        "Pass control to another controller"

        if addr < 0 or addr > 30:
            raise Vxi11Exception("Invalid address", 'pass_control')

        if self.link is None:
            self.open()

        flags = 0

        error, data_out = self.client.device_docmd(
            self.link,
            flags,
            self._timeout_ms,
            self._lock_timeout_ms,
            CMD_PASS_CTRL,
            True,
            4,
            struct.pack('!L', addr)
        )

        if error:
            raise Vxi11Exception(error, 'pass_control')

        return struct.unpack('!L', data_out)[0]

    def set_bus_address(self, addr):
        "Set interface device bus address"

        if addr < 0 or addr > 30:
            raise Vxi11Exception("Invalid address", 'set_bus_address')

        if self.link is None:
            self.open()

        flags = 0

        error, data_out = self.client.device_docmd(
            self.link,
            flags,
            self._timeout_ms,
            self._lock_timeout_ms,
            CMD_BUS_ADDRESS,
            True,
            4,
            struct.pack('!L', addr)
        )

        if error:
            raise Vxi11Exception(error, 'set_bus_address')

        self._bus_address = addr

        return struct.unpack('!L', data_out)[0]

    def send_ifc(self):
        "Send IFC"
        if self.link is None:
            self.open()

        flags = 0

        error, data_out = self.client.device_docmd(
            self.link,
            flags,
            self._timeout_ms,
            self._lock_timeout_ms,
            CMD_IFC_CTRL,
            True,
            1,
            b''
        )

        if error:
            raise Vxi11Exception(error, 'send_ifc')

    def find_listeners(self, address_list=None):
        "Find devices"
        if self.link is None:
            self.open()

        if address_list is None:
            address_list = list(range(31))
            address_list.remove(self._bus_address)

        found = []

        try:
            self.lock()
            for addr in address_list:
                # check for listener at primary address
                cmd = bytearray([GPIB_CMD_UNL, GPIB_CMD_UNT])
                cmd.append(self._bus_address | GPIB_CMD_TAD) # spec says this is unnecessary, but doesn't appear to work without this
                if type(addr) is tuple:
                    addr = addr[0]
                if addr < 0 or addr > 30:
                    raise Vxi11Exception("Invalid address", 'find_listeners')
                cmd.append(addr | GPIB_CMD_LAD)
                self.send_command(cmd)
                self.set_atn(False)
                time.sleep(0.0015) # probably not necessary due to network delays
                if self.test_ndac():
                    found.append(addr)
                else:
                    # check for listener at any sub-address
                    cmd = bytearray([GPIB_CMD_UNL, GPIB_CMD_UNT])
                    cmd.append(self._bus_address | GPIB_CMD_TAD) # spec says this is unnecessary, but doesn't appear to work without this
                    cmd.append(addr | GPIB_CMD_LAD)
                    for sa in range(31):
                        cmd.append(sa | GPIB_CMD_SAD)
                    self.send_command(cmd)
                    self.set_atn(False)
                    time.sleep(0.0015) # probably not necessary due to network delays
                    if self.test_ndac():
                        # find specific sub-address
                        for sa in range(31):
                            cmd = bytearray([GPIB_CMD_UNL, GPIB_CMD_UNT])
                            cmd.append(self._bus_address | GPIB_CMD_TAD) # spec says this is unnecessary, but doesn't appear to work without this
                            cmd.append(addr | GPIB_CMD_LAD)
                            cmd.append(sa | GPIB_CMD_SAD)
                            self.send_command(cmd)
                            self.set_atn(False)
                            time.sleep(0.0015) # probably not necessary due to network delays
                            if self.test_ndac():
                                found.append((addr, sa))
            self.unlock()
        except:
            self.unlock()
            raise

        return found


class Instrument(Device):
    "VXI-11 instrument interface client"

    def read_stb(self):
        "Read status byte"
        if self.link is None:
            self.open()

        flags = 0

        error, stb = self.client.device_read_stb(
            self.link,
            flags,
            self._lock_timeout_ms,
            self._timeout_ms
        )

        if error:
            raise Vxi11Exception(error, 'read_stb')

        return stb

    def remote(self):
        "Send remote command"
        if self.link is None:
            self.open()

        flags = 0

        error = self.client.device_remote(
            self.link,
            flags,
            self._lock_timeout_ms,
            self._timeout_ms
        )

        if error:
            raise Vxi11Exception(error, 'remote')

    def local(self):
        "Send local command"
        if self.link is None:
            self.open()

        flags = 0

        error = self.client.device_local(
            self.link,
            flags,
            self._lock_timeout_ms,
            self._timeout_ms
        )

        if error:
            raise Vxi11Exception(error, 'local')