High level server API

Device attribute command pipe

device_property class_property run() server_run()

This module provides a high level device server API. It implements TEP1. It exposes an easier API for developing a Tango device server.

Here is a simple example on how to write a Clock device server using the high level API:

import time
from tango.server import run
from tango.server import Device
from tango.server import attribute, command


class Clock(Device):

    time = attribute()

    def read_time(self):
        return time.time()

    @command(din_type=str, dout_type=str)
    def strftime(self, format):
        return time.strftime(format)


if __name__ == "__main__":
    run((Clock,))

Here is a more complete example on how to write a PowerSupply device server using the high level API. The example contains:

1. a read-only double scalar attribute called voltage
2. a read/write double scalar expert attribute current
3. a read-only double image attribute called noise
4. a ramp command
5. a host device property
6. a port class property

from time import time
from numpy.random import random_sample

from tango import AttrQuality, AttrWriteType, DispLevel
from tango.server import Device, attribute, command
from tango.server import class_property, device_property

class PowerSupply(Device):

    voltage = attribute()

    current = attribute(label="Current", dtype=float,
                        display_level=DispLevel.EXPERT,
                        access=AttrWriteType.READ_WRITE,
                        unit="A", format="8.4f",
                        min_value=0.0, max_value=8.5,
                        min_alarm=0.1, max_alarm=8.4,
                        min_warning=0.5, max_warning=8.0,
                        fget="get_current", fset="set_current",
                        doc="the power supply current")

    noise = attribute(label="Noise", dtype=((float,),),
                      max_dim_x=1024, max_dim_y=1024,
                      fget="get_noise")

    host = device_property(dtype=str)
    port = class_property(dtype=int, default_value=9788)

    def read_voltage(self):
        self.info_stream("get voltage(%s, %d)" % (self.host, self.port))
        return 10.0

    def get_current(self):
        return 2.3456, time(), AttrQuality.ATTR_WARNING

    def set_current(self, current):
        print("Current set to %f" % current)

    def get_noise(self):
        return random_sample((1024, 1024))

    @command(dtype_in=float)
    def ramp(self, value):
        print("Ramping up...")

if __name__ == "__main__":
    PowerSupply.run_server()

Pretty cool, uh?

Data types

When declaring attributes, properties or commands, one of the most important information is the data type. It is given by the keyword argument dtype. In order to provide a more pythonic interface, this argument is not restricted to the CmdArgType options.

For example, to define a SCALAR DevLong attribute you have several possibilities:

1. int
2. ‘int’
3. ‘int32’
4. ‘integer’
5. tango.CmdArgType.DevLong
6. ‘DevLong’
7. numpy.int32

To define a SPECTRUM attribute simply wrap the scalar data type in any python sequence:

• using a tuple: (:obj:`int`,) or
• using a list: [:obj:`int`] or
• any other sequence type

To define an IMAGE attribute simply wrap the scalar data type in any python sequence of sequences:

• using a tuple: ((:obj:`int`,),) or
• using a list: [[:obj:`int`]] or
• any other sequence type

Below is the complete table of equivalences.

dtype argument	converts to tango type
None	DevVoid
'None'	DevVoid
DevVoid	DevVoid
'DevVoid'	DevVoid
DevState	DevState
'DevState'	DevState
bool	DevBoolean
'bool'	DevBoolean
'boolean'	DevBoolean
DevBoolean	DevBoolean
'DevBoolean'	DevBoolean
numpy.bool_	DevBoolean
'char'	DevUChar
'chr'	DevUChar
'byte'	DevUChar
chr	DevUChar
DevUChar	DevUChar
'DevUChar'	DevUChar
numpy.uint8	DevUChar
'int16'	DevShort
DevShort	DevShort
'DevShort'	DevShort
numpy.int16	DevShort
'uint16'	DevUShort
DevUShort	DevUShort
'DevUShort'	DevUShort
numpy.uint16	DevUShort
int	DevLong
'int'	DevLong
'int32'	DevLong
DevLong	DevLong
'DevLong'	DevLong
numpy.int32	DevLong
'uint'	DevULong
'uint32'	DevULong
DevULong	DevULong
'DevULong'	DevULong
numpy.uint32	DevULong
'int64'	DevLong64
DevLong64	DevLong64
'DevLong64'	DevLong64
numpy.int64	DevLong64
'uint64'	DevULong64
DevULong64	DevULong64
'DevULong64'	DevULong64
numpy.uint64	DevULong64
DevInt	DevInt
'DevInt'	DevInt
'float32'	DevFloat
DevFloat	DevFloat
'DevFloat'	DevFloat
numpy.float32	DevFloat
float	DevDouble
'double'	DevDouble
'float'	DevDouble
'float64'	DevDouble
DevDouble	DevDouble
'DevDouble'	DevDouble
numpy.float64	DevDouble
str	DevString
'str'	DevString
'string'	DevString
'text'	DevString
DevString	DevString
'DevString'	DevString
bytearray	DevEncoded
'bytearray'	DevEncoded
'bytes'	DevEncoded
DevEncoded	DevEncoded
'DevEncoded'	DevEncoded
DevVarBooleanArray	DevVarBooleanArray
'DevVarBooleanArray'	DevVarBooleanArray
DevVarCharArray	DevVarCharArray
'DevVarCharArray'	DevVarCharArray
DevVarShortArray	DevVarShortArray
'DevVarShortArray'	DevVarShortArray
DevVarLongArray	DevVarLongArray
'DevVarLongArray'	DevVarLongArray
DevVarLong64Array	DevVarLong64Array
'DevVarLong64Array'	DevVarLong64Array
DevVarULong64Array	DevVarULong64Array
'DevVarULong64Array'	DevVarULong64Array
DevVarFloatArray	DevVarFloatArray
'DevVarFloatArray'	DevVarFloatArray
DevVarDoubleArray	DevVarDoubleArray
'DevVarDoubleArray'	DevVarDoubleArray
DevVarUShortArray	DevVarUShortArray
'DevVarUShortArray'	DevVarUShortArray
DevVarULongArray	DevVarULongArray
'DevVarULongArray'	DevVarULongArray
DevVarStringArray	DevVarStringArray
'DevVarStringArray'	DevVarStringArray
DevVarLongStringArray	DevVarLongStringArray
'DevVarLongStringArray'	DevVarLongStringArray
DevVarDoubleStringArray	DevVarDoubleStringArray
'DevVarDoubleStringArray'	DevVarDoubleStringArray
DevPipeBlob	DevPipeBlob
'DevPipeBlob'	DevPipeBlob