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DS1M12 usb osciloscope in linux and python

October 1st, 2008
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Well, today in the afternoon I was given a task, make the Usb Instruments DS1M12 usb osciloscope in linux, it was quite a surprise
to find out it had some kind of support for Linux and I started my work with their sources.

I found it requires two downloads one from USB Instruments itself and another from a thirdparty driver

Well, those two comes with some .so files you need to link your programs so you need to make sure
they have proper names like libDS1M12.so, libftd2xx.so and they can be found in the LD_LIBRARY_PATH or something like that, this is important.

After you get this solved it’s pretty straightforward with the USB Instruments package comes a good example you can use to understand their library, this took a bit of time since we(called some one to help me pinpoint some problems) could get it working and seeing the data flow quite fast, yet, it took us some time to discover that the sample code enabled the testmode and instead of real sampling, after that we could see the two channels sampling also the signal generator send out the example signals.

After this we agreed that it would be good to have a python interface to this osciloscope and I started working with swig to generare a proper wrapper around the USB Instruments library, around an hour ago I finished what we could call the first release of the interface and I’m being able to plot some data using matlplot lib. It took me a bit to figure how to manage to wrap some of the functions yet in the end swig and numpy solved all my issues.

I’m not really sure If I can release everything at the moment, I think I’ll have to ask USB Instruments since I use one of their headers to build the swig wrapper and it requires some minor modifications to make it work nicely so I would have to publish the modified header. If i get permission or any idea how I should publish the repository, it will be here at valkertown Mercurial Repositories

For now you have to beleive me that now the use of this osciloscope it’s reduced to something like this

  1.  
  2. """
  3.   Author: Carlos Andres Perilla
  4.   Centro Internacional de Física, Bogotá-Colombia.
  5.  
  6.   This program is free software: you can redistribute it and/or
  7.   modify it under the terms of the GNU Affero General Public License
  8.   as published by the Free Software Foundation, either version 3 of
  9.   the License, or (at your option) any later version.
  10.  
  11.   This program is distributed in the hope that it will be useful, but
  12.   WITHOUT ANY WARRANTY; without even the implied warranty of
  13.   MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the GNU
  14.   Affero General Public License for more details.
  15.  
  16.   You should have received a copy of the GNU Affero General Public
  17.   License along with this program.  If not, see
  18.   <http://www.gnu.org/licenses/>.
  19.  
  20. """
  21.  
  22. from Osciloscope import UsbOsciloscope
  23. from pylab import *
  24. import time
  25.  
  26. o = UsbOsciloscope()
  27. # Load the firmare into the osciloscope FPGA, this the RFB that comes in the USBI pack.
  28. o.program()
  29. # Enables both channels for sampling
  30. o.set_channels()
  31.  
  32. while True:
  33.     # Start signal, it gets some other params like
  34.     # triggering configuration, port conf and a lot of other things
  35.     o.start_scan()
  36.     status = -1
  37.     while status != 0:
  38.         # Do the actual reading of a single frame
  39.         retval = o.get_data()
  40.         status = retval[0]
  41.         if status != 0:
  42.             # Since the buffers can be large and the according
  43.             # to the sampling rate we may need to wait a bit
  44.             time.sleep(0.01)
  45.         else:
  46.             # If we got the data successfully we can now plot what we got using
  47.             # matplot lib.
  48.             values = retval[5].dwNumValuesReturned
  49.             x_axis = arange(0,values,1)
  50.             plot(x_axis ,retval[2][0:values],‘r–’,x_axis,retval[3][0:values],‘bs’)
  51.             show()
  52.  

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