SchunkMotionProtocol 0.2.2

Schunk Motion Protocol for Python

Documentation:

http://schunk.rtfd.org/

Code:

http://github.com/spatialaudio/schunk/

Python Package Index:

http://pypi.python.org/pypi/SchunkMotionProtocol/

Schunk Motion Protocol manual:

http://www.schunk.com/schunk_files/attachments/MotionControl_en_2010-03.pdf

A newer version of the manual is available in a huge zip file from the Schunk website (have a look in the directory Manuals/Motion Control/)

Disclaimer

This is not a commercial product and the author has no relation whatsoever to SCHUNK GmbH & Co. KG.

Use at your own risk!

Devices

Only 1 device was tested: Schunk PR-70 Servo Electric Swivel Unit.

Defaults for this device: serial (RS232), baudrate=9600, module ID 11 (0x0B).

Other devices may or may not work.

Only firmware version 1.56 was tested, other versions may or may not work.

Requirements

Obviously, Python is required. Any version >= 2.7 should do.

Typically, PySerial handles the serial connection, but any library with a similar API can be used.

py.test is used for the tests.

Limitations

Only a subset of the Schunk Motion Protocol is supported.

Only the direct response to a command can be obtained, impulse messages are not supported. One exception is the “CMD POS REACHED” impulse message which is used to realize movement commands which are waiting until the movement is finished, e.g. move_pos_blocking().

Only floating point unit systems are supported.

The connection is opened and closed for each message. Keeping the connection open is not supported.

Only serial communication is implemented. No CAN, no Profibus.

Installation

Using pip, you can download and install the latest release with a single command:

pip install --user SchunkMotionProtocol

If you want to install it system-wide for all users (assuming you have the necessary rights), you can just drop the --user option.

To un-install, use:

pip uninstall SchunkMotionProtocol

If you prefer, you can also download the package from PyPI, extract it, change to the main directory and install it using:

python setup.py install --user

If you want to get the newest development version from Github:

git clone https://github.com/spatialaudio/schunk.git
cd schunk
python setup.py install --user

Alternatively, you can just copy schunk.py to your working directory.

If you want to make changes to the code, you should type:

python setup.py develop --user

or, alternatively:

pip install --user -e .

… where -e stands for --editable.

Tests

Tests are implemented using py.test, run this in the main directory:

python setup.py test

Examples

This should get you started:

import schunk
import serial

mod = schunk.Module(schunk.SerialConnection(
    0x0B, serial.Serial, port=0, baudrate=9600, timeout=1))

mod.move_pos(42)

Use the ID of your Schunk module instead of 0x0B.

See the documentation of PySerial for all possible serial port options. You probably only have to change port, e.g. port='/dev/ttyS1' or port='COM3'.

It is useful to specify a timeout, otherwise you may have to wait forever for the functions to return if there is an error. On the other hand, if you want to use the blocking commands (*_blocking()), you should disable the timeout (or make it longer than the expected movement times).

If the parameters for your setup don’t change, you can write them into a separate file, e.g. with the name myschunk.py:

import schunk
import serial

module1 = schunk.Module(schunk.SerialConnection(
    0x0B, serial.Serial, port=0, baudrate=9600, timeout=1))

and then use it like this in all our scripts:

from myschunk import module1
module1.move_pos(42)

The file myschunk.py must be in the current directory for this to work.

If you are an object-oriented kind of person, you can of course also write your own class:

import schunk
import serial

class MySchunkModule(schunk.Module):
    def __init__(self):
        schunk.Module.__init__(self, schunk.SerialConnection(
            0x0B, serial.Serial, port=0, baudrate=9600, timeout=1))

module1 = MySchunkModule()
module1.move_pos(42)