PIPython 2.7.0.14

Collection of libraries to use PI devices and process GCS data.

PIPython

PIPython is a collection of Python modules to access a PI device and process GCS data. It can be used with Python 3.6+ on Windows, Linux and OS X and without the GCS DLL also on any other platform.

Installation

By using PIPython you agree to the license agreement, see the provided file:

eula.md

From local folder

Unzip the file PIPython.zip, open a command entry (Linux Console or Windows CMD window) and run:

python setup.py install

For further reading open the index.html file in your browser and see the samples in the samples folder.

From GitHub

PIPython on GitHub

git clone [e-mail]:PI-PhysikInstrumente/PIPython.git
python setup.py install

From pypi.org

pip install PIPython    

Feedback

We appreciate your feedback at:

[e-mail]

Quickstart

Communicate to a PI device via GCSDevice which wraps the GCS DLL functions and provides methods to connect to the device. Call GCSDevice with the controller name as argument.

from pipython import GCSDevice
pidevice = GCSDevice('C-884')
pidevice.InterfaceSetupDlg()
print pidevice.qIDN()
pidevice.CloseConnection()

GCSDevice is a context manager which closes the connection if an exception raises inside the with statement.

from pipython import GCSDevice
with GCSDevice('C-884') as pidevice:
    pidevice.InterfaceSetupDlg()
    print(pidevice.qIDN())

See also the provided samples in the samples subdirectory. Start with quickstart.py.

Requirements

Download these python packages with pip install:

• PyUSB
• PySocket
• PySerial

With pipython.interfaces.piusb you can connect a USB device without using the GCS DLL. This works only with Linux and requires LibUSB which usually is provided by the OS.

Arguments

From now on pidevice refers to a connected GCSDevice instance.

Setter functions

Usually you can call a setter function with

• a dictionary of axes/channels and values
• a list for axes/channels and a list of the values
• a single item for axis/channel and a single value

gcs.MOV({'X': 1.23, 'Y': 2.34})
gcs.MOV(['X', 'Y'], [1.23, 2.34])
gcs.MOV('X', 1.23)

For channels and numeric axis names you can omit the quotes.

gcs.MOV({1: 1.23, 2: 2.34})
gcs.MOV([1, 2], [1.23, 2.34])
gcs.MOV(1, 1.23)

Getter functions

GCS 2.0

Usually getter commands can be called with

• a list of axes/channels.
• a single item for axis/channel, without quotes if numeric
• without any arguments which will return the answer for all available axes/channels

gcs.qPOS(['X', 'Y'])
gcs.qPOS('X')
gcs.qPOS(1)
gcs.qPOS()

GCS 3.0

Usually getter commands can be called with

• a single axis
• without any arguments which will return the answer for all available axes

gcs.qPOS('AXIS_1')
gcs.qPOS()

Return values

Axes or channel related answers are returned as (ordered) dictionary.

pidevice.qPOS()
>>>{'X': 1.23, 'Y': 2.34}

If you do not provide arguments you always have to use strings as keys.

pos = pidevice.qPOS()
print(pos['1'])

The following sample will move all axes to targets and waits until the motion has finished. It shows how to use only the values from the returned dictionary.

from time import sleep
...
pidevice.MOV(axes, targets)
while not all(list(pidevice.qONT(axes).values())):
    sleep(0.1)

GCS 2.0

If you provide arguments their types are preserved and you can use these as keys.

pos = pidevice.qPOS([1, 2, 3])
print(pos[1])

GCS 3.0

If you provide arguments their types are preserved and you can use these as keys.

pos = pidevice.qPOS('AXIS_1') # only one axis is possible
print(pos['AXIS_1'])

Some hints...

Helpers

In pipython.pitools you will find some helper funtions for your convenience. See the provided samples for how to use them. The sample above can then be written as:

from pipython import pitools
...
pidevice.MOV(axes, targets)
pitools.waitontarget(pidevice, axes)

Enable debug logging

To log debug messages on the console just enter these lines prior to calling GCSDevice.

from pipython import PILogger, DEBUG, INFO, WARNING, ERROR, CRITICAL

PILogger.setLevel(DEBUG)

GCSError and error check

By default an "ERR?" command is sent after each command to query if an error occurred on the device which then will be raised as GCSError exception. If communication speed is an issue you can disable error checking.

pidevice.errcheck = False

To handle a catched GCSError exception you can use the defines provided by gcserror instead of pure numeric values. Remember the difference between GCSError which is the exception class and gcserror which is the according module.

from pipython import GCSDevice, GCSError, gcserror
with GCSDevice('C-884') as pidevice:
    try:
        pidevice.MOV('X', 1.23)
    except GCSError as exc:
        if exc == gcserror.E_1024_PI_MOTION_ERROR:
            print('There was a motion error, please check the mechanics.')
        else:
            raise

The exception class GCSError will translate the error code into a readable message.

from pipython import GCSError, gcserror
raise GCSError(gcserror.E_1024_PI_MOTION_ERROR)
>>>GCSError: Motion error: position error too large, servo is switched off automatically (-1024)

GCS 3.0

• to reset the error state of 1 or more axes

for axis in device.axes:
    if axis_has_error(device):
        while check_axis_status_bit(device, axis, AXIS_STATUS_FAULT_REACTION_ACTIVE):
            pass
        print('reset axis error: ', axis)
        device.RES(axis)

Big data

Commands like qDRR() for GCS 2.0 syntax, or qREC_DAT() for GCS 3.0 syntax which read a large amount of GCS data return immediately with the header dictionary containing information about the data. Then they will start a background task that carries on reading data from the device into an internal buffer. The bufstate property returns the progress of the reading as floating point number in the range 0 to 1 and turns to True when reading has finished. Hence, when using it in a loop check for is not True. (Remember, this is not the same as != True.)

GCS 2.0

header = pidevice.qDRR(1, 1, 8192)
while pidevice.bufstate is not True:
    print('read data {:.1f}%...'.format(pidevice.bufstate * 100))
    sleep(0.1)
data = pidevice.bufdata

GCS 3.0

header = pidevice.qREC_DAT('REC_1', 'ASCII', 1, 1, 8192)
while pidevice.bufstate is not True:
    print('read data {:.1f}%...'.format(pidevice.bufstate * 100))
    sleep(0.1)
data = pidevice.bufdata

Textual interface

Besides the functions implemented in GCSCommands you can send GCS commands as strings to the controller. Use read() for commands returning an answer, read_gcsdata() for commands returning GCS data and send() for non-answering commands.

print(pidevice.read('POS?'))
print(pidevice.read_gcsdata('DRR? 1 100 1'))
pidevice.send('MOV X 1.23')

They return the raw string or GCS data from the controller. If errorcheck is enabled the error state is queried from the device automatically. We recommend to use the provided functions instead of sending raw strings.

In line with the C++ GCS DLL the functions ReadGCSCommand() and GcsCommandset() are also available. They will never query an error from the device.

print(pidevice.ReadGCSCommand('POS?'))
pidevice.GcsCommandset('MOV X 1.23')