{"id":10238,"date":"2013-12-15T22:04:34","date_gmt":"2013-12-16T03:04:34","guid":{"rendered":"http:\/\/scruss.com\/blog\/?p=10238"},"modified":"2021-02-25T11:11:59","modified_gmt":"2021-02-25T16:11:59","slug":"my-raspberry-pi-talks-to-my-oscilloscope","status":"publish","type":"post","link":"https:\/\/scruss.com\/blog\/2013\/12\/15\/my-raspberry-pi-talks-to-my-oscilloscope\/","title":{"rendered":"My Raspberry Pi talks to my Oscilloscope"},"content":{"rendered":"

Hey!<\/span> This post is completely ancient<\/span>. It doesn’t even use Python 3. Advice given here might be well out of date.<\/p>\n

\n

\u00e2\u20ac\u00a6 it complains that the oscilloscope is always making waves.<\/p>\n

\"DS1EB134907266_0\"<\/p>\n

Ahem. Anyway. I have a Rigol DS1102E 100 MHz Digital Oscilloscope<\/a>. For such a cheap device, it’s remarkable that you can control it using USB Test & Measurement Class<\/a> commands. I’d been wanting to use a Raspberry Pi as a headless data acquisition box with the oscilloscope for a while, but Raspbian doesn’t ship with the usbtmc kernel module. I thought I was stuck.<\/p>\n

Alex Forencich turned up in the forum<\/a> with an all-Python solution: Python USBTMC<\/a> (source: alexforencich \/ python-usbtmc<\/a>). I got this working quite nicely today on both the Raspberry Pi and my Ubuntu laptop. Here’s how I installed it:<\/p>\n

    \n
  1. Check your device’s USB code with lsusb:
    \n$ lsusb <\/span>
    \nBus 001 Device 002: ID 0424:9512 Standard Microsystems Corp. <\/span>
    \n\u00e2\u20ac\u00a6.<\/span>
    \nBus 001 Device 004: ID 1ab1:0588 Rigol Technologies DS1000 SERIES<\/strong><\/span><\/li>\n
  2. Ensure that libusb-1.0 is installed:
    \nsudo apt-get install libusb-1.0-0<\/span><\/li>\n
  3. Create a new group, usbtmc:
    \nsudo groupadd usbtmc<\/span><\/li>\n
  4. Add yourself to this group:
    \nsudo usermod -a -G usbtmc pi<\/span><\/li>\n
  5. As root, create a file \/etc\/udev\/rules.d\/usbtmc.rules<\/span>. You’ll need to put in your device’s ID values:
    \n# USBTMC instruments<\/span>
    \n# Rigol DS1100 – ID 1ab1:0588 Rigol Technologies DS1000 SERIES<\/span>
    \nSUBSYSTEMS==”usb”, ACTION==”add”, ATTRS{idVendor}==”1ab1″, ATTRS{idProduct}==”0588″, GROUP=”usbtmc”, MODE=”0660″<\/span>
    \n(all of the SUBSYSTEMS<\/em> to MODE=<\/em> should be one one line)<\/li>\n
  6. Download and install the latest pyusb (Raspbian version is rather old):
    \ngit clone https:\/\/github.com\/walac\/pyusb.git<\/span>
    \ncd pyusb<\/span>
    \npython setup.py build<\/span>
    \nsudo python setup.py install<\/span><\/li>\n
  7. Now get python-usbtmc:
    \ngit clone https:\/\/github.com\/alexforencich\/python-usbtmc.git<\/span>
    \ncd python-usbtmc<\/span>
    \npython setup.py build<\/span>
    \nsudo python setup.py install<\/span><\/li>\n
  8. For this simple demo, you’ll need to convert the USB vendor IDs to decimal:
    \n0x1ab1 = 6833<\/span>
    \n0x0588 = 1416<\/span><\/li>\n
  9. Now, start python as root (sudo python<\/span>) then type:
    \nimport usbtmc<\/span>
    \ninstr =\u00c2\u00a0 usbtmc.Instrument(6833, 1416)<\/span>
    \nprint(instr.ask(“*IDN?”))<\/span><\/li>\n
  10. This should<\/em> return something like:
    \nRigol Technologies,DS1102E,DS1EB13490xxxx,00.02.06.00.01<\/span><\/li>\n<\/ol>\n

    If you get the status line, congratulations! You now have a fully working usbtmc link.\u00c2\u00a0I haven’t had much time to play with this, but I know I can make really nice screenshots to an attached USB drive using the command: instr.write(“:HARDcopy”)<\/span>. Many more commands can be found in the DS1000D\/E Programming Guide<\/strong>, available on Rigol<\/a>‘s site.<\/p>\n

    I had a couple of problems, though:<\/p>\n

      \n
    1. The library seems to need root privileges, despite the udev rule thing<\/del>. After creating the udev rule, you will need to reboot. This is the simplest way of getting it to work without being root.<\/li>\n
    2. Reading from the ‘scope’s memory\u00c2\u00a0 chokes on non-UTF8 characters. If I do:<\/del>
      \n rawdata = instr.ask(“:WAV:DATA? CHAN1”)[10:]<\/span><\/del>
      \n I get a lengthy Python error which ends:<\/del>
      \n \u00e2\u20ac\u00a6<\/del>
      \n File “\/usr\/lib\/python2.7\/encodings\/utf_8.py”, line 16, in decode<\/span><\/del>
      \n \u00c2\u00a0\u00c2\u00a0\u00c2\u00a0 return codecs.utf_8_decode(input, errors, True)<\/span><\/del>
      \n UnicodeDecodeError: ‘utf8’ codec can’t decode byte 0x99 in position 10: invalid start byte<\/span><\/del>
      \n I have no idea what that means, or how to fix it<\/del>. Alex suggested using ask_raw instead of ask, and the data comes through with no complaints.<\/li>\n<\/ol>\n

      I’ve still got to work my way through the Rigol’s data format, but other people have done that before:<\/p>\n

        \n
      1. Controlling a Rigol oscilloscope using Linux and Python | C i b o M a h t o . c o m<\/a><\/li>\n
      2. Ken Shirriff’s blog: Four Rigol oscilloscope hacks with Python<\/a><\/li>\n<\/ol>\n

        I’ll post any updates here, along with the Raspberry Pi forum topic: USB Test & Measurement class (usbtmc) driver?<\/a><\/p>\n

        Incidentally, if you’re working with WFM data dumps from the Rigol ‘scopes (and you should, because they make storing data to USB drives quick), mabl\/pyRigolWFM<\/a> is basically magic. Not merely can it describe and decode those binary files, it can do pretty graphics with no thought required:<\/p>\n

        \"made<\/a>Hat tip for the mention: MP3 Options & Oscilloscope Interfacing For Raspberry Pi @Raspberry_Pi #piday #raspberrypi \u00c2\u00ab adafruit industries blog<\/a><\/p>\n

        Update, 2013-12-20<\/strong>: I’ve successfully managed to run most of Ken’s examples<\/a> with Alex’s code. The major modification you have to do is use ask_raw<\/span> instead of ask<\/span>. Example code shown below:<\/p>\n

        \n#!\/usr\/bin\/python\n# -*- coding: utf-8 -*-\n\n"""\nDownload data from a Rigol DS1102E oscilloscope and graph with matplotlib\n         using  Alex Forencich's python-usbtmc pure python driver\n                https:\/\/github.com\/alexforencich\/python-usbtmc\nscruss - 2013-12-20\n\nbased on\nDownload data from a Rigol DS1052E oscilloscope and graph with matplotlib.\nBy Ken Shirriff, http:\/\/righto.com\/rigol\n\nwhich in turn was\nBased on http:\/\/www.cibomahto.com\/2010\/04\/controlling-a-rigol-oscilloscope-using-linux-and-python\/\nby Cibo Mahto.\n"""\n\nimport usbtmc\nimport time\nimport numpy\nimport matplotlib.pyplot as plot\n\n# initialise device\ninstr =  usbtmc.Instrument(0x1ab1, 0x0588) # Rigol DS1102E\n\n# read data\ninstr.write(":STOP")\ninstr.write(":WAV:POIN:MODE RAW")\n# first ten bytes are header, so skip\nrawdata = instr.ask_raw(":WAV:DATA? CHAN1")[10:]\ndata_size = len(rawdata)\n\n# get metadata\nsample_rate = float(instr.ask_raw(':ACQ:SAMP?'))\ntimescale = float(instr.ask_raw(":TIM:SCAL?"))\ntimeoffset = float(instr.ask_raw(":TIM:OFFS?"))\nvoltscale = float(instr.ask_raw(':CHAN1:SCAL?'))\nvoltoffset = float(instr.ask_raw(":CHAN1:OFFS?"))\n\n# show metadata\nprint "Data size:      ", data_size\nprint "Sample rate:    ", sample_rate\nprint "Time scale:     ", timescale\nprint "Time offset:    ", timeoffset\nprint "Voltage offset: ", voltoffset\nprint "Voltage scale:  ", voltscale\n\n# convert data from (inverted) bytes to an array of scaled floats\n# this magic from Matthew Mets\ndata = numpy.frombuffer(rawdata, 'B')\ndata = data * -1 + 255\ndata = (data - 130.0 - voltoffset\/voltscale*25) \/ 25 * voltscale\n\n# creat array of matching timestamps\ntime = numpy.linspace(timeoffset - 6 * timescale, timeoffset + 6 * timescale,\n                      num=len(data))\n\n# scale time series and label accordingly\nif (time[-1] &amp;lt; 1e-3):\n    time = time * 1e6\n    tUnit = "\u00c2\u00b5S"\nelif (time[-1] &amp;lt; 1):\n    time = time * 1e3\n    tUnit = "mS"\nelse:\n    tUnit = "S"\n\n# Plot the data\nplot.plot(time, data)\nplot.title("Oscilloscope Channel 1")\nplot.ylabel("Voltage (V)")\nplot.xlabel("Time (" + tUnit + ")")\nplot.xlim(time[0], time[-1])\nplot.show()\n<\/pre>\n","protected":false},"excerpt":{"rendered":"
        Hey! This post is completely ancient. It doesn’t even use Python 3. Advice given here might be well out of date. \u00e2\u20ac\u00a6 it complains that the oscilloscope is always making waves. Ahem. Anyway. I have a Rigol DS1102E 100 MHz Digital Oscilloscope. For such a cheap device, it’s remarkable that you can control it using […]<\/p>\n","protected":false},"author":2,"featured_media":0,"comment_status":"open","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"_jetpack_memberships_contains_paid_content":false,"footnotes":"","jetpack_publicize_message":"","jetpack_publicize_feature_enabled":true,"jetpack_social_post_already_shared":true,"jetpack_social_options":{"image_generator_settings":{"template":"highway","default_image_id":0,"font":"","enabled":false},"version":2}},"categories":[7],"tags":[1286,2506,2540,2510,2536,2760,229,2756],"class_list":["post-10238","post","type-post","status-publish","format-standard","hentry","category-computers-suck","tag-debian","tag-oscilloscope","tag-python","tag-raspberrypi","tag-raspbian","tag-rigol","tag-usb","tag-usbtmc"],"jetpack_publicize_connections":[],"jetpack_featured_media_url":"","jetpack_shortlink":"https:\/\/wp.me\/pQNZZ-2F8","jetpack_sharing_enabled":true,"_links":{"self":[{"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/posts\/10238","targetHints":{"allow":["GET"]}}],"collection":[{"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/posts"}],"about":[{"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/types\/post"}],"author":[{"embeddable":true,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/users\/2"}],"replies":[{"embeddable":true,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/comments?post=10238"}],"version-history":[{"count":9,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/posts\/10238\/revisions"}],"predecessor-version":[{"id":16641,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/posts\/10238\/revisions\/16641"}],"wp:attachment":[{"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/media?parent=10238"}],"wp:term":[{"taxonomy":"category","embeddable":true,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/categories?post=10238"},{"taxonomy":"post_tag","embeddable":true,"href":"https:\/\/scruss.com\/blog\/wp-json\/wp\/v2\/tags?post=10238"}],"curies":[{"name":"wp","href":"https:\/\/api.w.org\/{rel}","templated":true}]}}