USB oscilloscope for troublshooting?

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Has anybody used a USB sound capture device for an audio frequency
oscilloscope on a Raspberry Pi? xoscope is available using apt,
but I can't find any reference to what sound devices, if any, it
can use over USB.

If there are other USB oscilloscope options worth looking at
please post. I don't specifically need RF performance, but if
it's available it's worth a look.

Thanks for reading,

bob prohaska


Re: USB oscilloscope for troublshooting?
bob prohaska wrote:

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look at SDR software defined radio. Especially receivers are ~20,- US$ range

Re: USB oscilloscope for troublshooting?
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It is worth understanding what frequency range you're interested in.
Soundcards are typically 20Hz-20kHz.
SDR often has a limited bandwidth and doesn't go below ~30MHz.

Often for oscilloscope purposes you're interested in DC, which is outside
the range of this hardware.  Soundcards may go that low, or maybe it can if
you remove a series capacitor.

Theo

Re: USB oscilloscope for troublshooting?
On 21/04/2021 17:30, Theo wrote:
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not built mine yet (too much trigger happy shopping, it's sat on a shelf).

Kuman JYE DSO Shell Oscilloscope DIY Kit with Open Source 2.4 inch color  
TFT LCD+ Shell + DIY Parts + Probe 15001K (SMD pre-soldered)
https://www.amazon.co.uk/gp/product/B01MY7HAFG

--  
Adrian C

Re: USB oscilloscope for troublshooting?
On 21/04/2021 18:15, Adrian Caspersz wrote:
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you can buy a second hand real scope for not much more...

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--  
?The ultimate result of shielding men from the effects of folly is to  
fill the world with fools.?

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Re: USB oscilloscope for troublshooting?
Theo wrote:

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Ah, sorry I understood the opposite - I missed or misunderstood "I don't
specifically need RF performance" as if OP was asking for RF explicitely :)

I know only the PicoScope from the Automotive angle, but could be there are
cheaper products that work with linux.

Re: USB oscilloscope for troublshooting?
On Wed, 21 Apr 2021 20:22:27 +0200

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Hantek is the name, or at least one of the names, many people rebadge
them. There is openhantek6022 which works for the cheapest scope.

It's OK for DC and audio, which is all I need these days. If I have
frequencies a bit higher to deal with, I haul out my ancient Tek 465B,
which weighs about fifty times as much as the Hantek device.

--  
Joe


Re: USB oscilloscope for troublshooting?
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Hantek seems to be Windows-oriented, I have great respect for Tektronix,
but analog scopes are no help with transients absent a Polaroid camera
and a stable trigger pulse.  

Thanks for writing,

bob prohaska
  

Re: USB oscilloscope for troublshooting?
On Thu, 22 Apr 2021 05:03:16 -0000 (UTC)

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That's why I mention openhantex6022. It's specific to the 6022 but it's
native Linux, later ported to Windows. I never found the Hantek supplied
Windows software to be much good at triggering.

--  
Joe


Re: USB oscilloscope for troublshooting?
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I'm impressed. Downloaded the tarball and had it built in a few minutes
on an 8GB Pi4 running raspberrypi 5.10.17-v7l+ #1403 SMP  
Mon Feb 22 11:33:35 GMT 2021. Run  without installing it reports:

bob@raspberrypi:~/OpenHantek-openhantek-e7e0c7b $ ./build/openhantek/OpenHantek  
libEGL warning: DRI2: failed to authenticate
qt5ct: using qt5ct plugin
QEGLPlatformContext: Failed to create context: 3009
libpng warning: iCCP: known incorrect sRGB profile
BlueALSA detected - Disabling audio sandbox
libEGL warning: DRI2: failed to authenticate

Not sure how important the errors are, I didn't install, nor mess with the
devd permissions. It doesn't seem to recognize demo mode, has the flag option
changed? I'd like to see the demo mode before running out and buying hardware.

Are there any other tests worth doing before buying some hardware?  

Thanks for writing!

bob prohaska


Re: USB oscilloscope for troublshooting?
On Fri, 23 Apr 2021 00:55:35 -0000 (UTC)

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Re: USB oscilloscope for troublshooting?
On Fri, 23 Apr 2021 00:55:35 -0000 (UTC)

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Sorry, hit send by accident.

I can't help really, openhantek was in the sid repository so I just
installed it with apt. I assume it is no longer maintained, as the
Debian package database claims never to have heard of it. Probably best
avoided then.

I haven't used it for a while, and it's not a problem as I need to
maintain a portable Windows machine for a number of reasons, of which
this scope was one. I have other niche hardware for which only Windows
will do. And no, I'm not going to try Wine, I've had a go with it in
the past, and it has always seemed rather flaky when dealing with
unusual peripherals and fairly high speeds. I assume that programmers
of the Windows drivers tend to cut corners.

--  
Joe  


Re: USB oscilloscope for troublshooting?
On Thu, 22 Apr 2021 05:03:16 +0000, bob prohaska wrote:

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That depends on the scan rate: when I used mine to measure battery state  
I ran the scan slowly enough the stretch the recovery signal across 30%  
or so of the scan, so the time for the scan to cross the screen was  
around 20 - 40 mS, and I fiddled with the scan trigger so that the  
voltage drop as the solenoid pulled in triggered a single shot scan,  

I think most 'scopes can be set to this triggering mode and low scan  
speed, though its quite understandable that you'd not be familiar with  
this way of using a scope if you've never needed to observe such  
relatively slow events.  

My scope's minimum scan speed is 200 mS/division, or 2 seconds to cross  
the whole screen, so I'd have been running it at 10-15 ms/division to do  
the battery condition check.

It helps to turn the brightness up enough that the whole scan is done  
before the image fades.

FWIW the triggering device was a timer used to 'dethermalise', i.e. bring  
down, a gliding model aircraft if it was still flying after a preset  
time, typically three minutes after a switch on the towhook was last  
operated as the model was launched from the top of its towline, so I set  
that to 6 seconds (its smallest interval) during battery testing. The  
battery being checked was a 4-5 cell NiCd used to drive the timer.  

To see a trace, I simply flipped the towhook to start the timer and 6  
seconds later the timer tripped and my scope drew a single trace across  
the screen, which was easily visible long enough to see the shape of the  
voltage drop and recovery and to measure the depth of the drop.  


--  
Martin    | martin at
Gregorie  | gregorie dot org


Re: USB oscilloscope for troublshooting?

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I've got a bottom of the range Picoscope, and I'm very pleased with it.
This thread prompted me to search for the Hantek 6022, which seems to
cost a similar price to the Picoscope, but Picoscope has faster sample
rates and a wider range of input sensitivities, so, in my estimation,
it's better value for money than the Hantek.

But it all depends on what specification you need, and what compromises
you're willing to make, money being one of them.

David

Re: USB oscilloscope for troublshooting?
On 2021-04-20 20:05, bob prohaska wrote:
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all you really need is a decent A:D with a good bandwidth.

Then RPi could use SPI or I2C to talk to it.  Then you can make a  
charting application to display the trace, or use an existing one [I  
assume such things have been done before, it's not a new idea]

Sound card o-scope would limit to audio bandwidth.  An A:D that can run  
at frequencies from DC to above 1Mhz is probably what you want.  Maybe  
an ADC that is capable of doing video would work... [you'll have to  
search but I remember seeing them]


--  
(aka 'Bombastic Bob' in case you wondered)

'Feeling with my fingers, and thinking with my brain' - me

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Re: USB oscilloscope for troublshooting?
On Wed, 21 Apr 2021 03:05:36 +0000, bob prohaska wrote:

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I suspect you'll get better suggestions if you can outline what you are  
trying to do.

For instance, are you trying to get analogue output from digital  
recordings or do you want to digitise audio from a mic or turntable?

What pert of the system (analogue or digital) do you need to trouble-
shoot?

A 'scope may be best for audio signals, but something as simple as a  
logic probe may be good enough to sort out problems on the digital side.


--  
Martin    | martin at
Gregorie  | gregorie dot org


Re: USB oscilloscope for troublshooting?
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My hope was to elicit reports of practical experience....

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The motivating problem is monitoring power supply voltage on a Raspberry
Pi4 during boot and disk spin-up. I'd like to see the voltage rise, sag
during boot and spin-up and then stabilize. Depth and duration of the
sag would be the most essential observation.  


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Basically power supply circuits. A "stop trigger" that halts recording
when something interesting happens is much desired.

Thanks for writing!

bob prohaska




Re: USB oscilloscope for troublshooting?
declaimed the following:


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    If you are willing to change platform, you might find more
candidates...

https://create.arduino.cc/projecthub/Meeker6751/arduino-oscilloscope-6-channel-674166?ref=tag&ref_id=oscilloscope&offset=0
Unfortunately, that one only goes up to 1kHz -- didn't check for Windows vs
Linux

https://create.arduino.cc/projecthub/zaidatek/zaidascope-arduino-oscilloscope-8-ch-max-100-khz-c774f5?ref=tag&ref_id=oscilloscope&offset=1
100kHz, but may be too heavily tied to Windows for display purposes

https://create.arduino.cc/projecthub/wayri/arduino-oscilloscope-84b2ac?ref=tag&ref_id=oscilloscope&offset=5
2 channel but with its own display

https://www.amazon.com/DSO138-Oscilloscope-Digital-Handheld-Version/dp/B088FWHKZG/ref=asc_df_B088FWHKZG/?tag=hyprod-20&linkCode=df0&hvadid47%7379495345&hvpos=&hvnetw=g&hvrand75%21356089507600023&hvpone=&hvptwo=&hvqmt=&hvdev=c&hvdvcmdl=&hvlocint=&hvlocphy90%17241&hvtargid=pla-1040797794422&psc=1
single channel


--  
    Wulfraed                 Dennis Lee Bieber         AF6VN
     snipped-for-privacy@ix.netcom.com    http://wlfraed.microdiversity.freeddns.org/

Re: USB oscilloscope for troublshooting?
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Xoscope's webpage says it supports ALSA as an input source, so as
long as a USB audio adapter is working with ALSA (the cheap Chinese
ones seem to do so without issues) it should be fine.

It will have a series capacitor to block DC. You'll need to either
remove this (might be difficult if it's a small indistinct-looking
SMD part) or use a chopper circuit like this if you want to measure
DC signals:
http://lea.hamradio.si/~s57uuu/scdsp/CheapChop/cheapchop.htm

For more sensible input impedence (so the behaviour of the circuit
doesn't change when you probe it), the buffer circuit shown at the
xoscope homepage would also be recommended:
http://xoscope.sourceforge.net/hardware/hardware.html

Of course at this point you've got a significant amount of
front-end circuitry for your "simple" sound card oscilloscope. For
a data logging application that might be quite reasonable, but for
basic troubleshooting maybe it would be easier to just buy an old
CRO (Cathode Ray Oscilloscope), which has the added benefit of
working outside the audio frequency range.

--  
__          __
#_ < |\| |< _#

Re: USB oscilloscope for troublshooting?
On Wed, 21 Apr 2021 23:25:23 +0000, Computer Nerd Kev wrote:

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There are some decent dual channel, 20MHz oscilloscopes appearing on eBay  
and at pretty reasonable prices too. Find one locally if possible to same  
freight costs: a good older 'scope is both heavy and bulky.  

Also, its worth noting that a 'scope can also be used as a logic probe: a  
straight high line is a stable '1', a straight low line is a stable '0'  
and either a pair of lines or a square wave, depending on scope scan  
speed vs signal frequency, indicates a digital signal.

Mine is a dual beam 20MHz Hameg I've had since the mid '80s and used for  
everything from trouble-shooting a floppy drive interface I built for a  
6809 system to checking the state of 50mAH NiCd batteries (they were used  
in a timer to pulse a solenoid with a 500mA, 15mS pulse: the shape, depth  
and width of the of the battery's voltage drop when the solenoid was  
operated was an excellent indication of battery condition. As it aged the  
voltage drop changed progressively from a 15mS wide drop with a flat  
bottom and instant recovery to a deeper, wider shape with no flat bottom  
and a longer recovery slope. When the flat bottom was gone it was time to  
replace the NiCds.  

  
--  
Martin    | martin at
Gregorie  | gregorie dot org


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