USB oscilloscope for troublshooting?

[bob prohaska]

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

[Deloptes]

bob prohaska wrote:

> 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.

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

[Theo]

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

[Big Bad Bob]

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

'your story is so touching, but it sounds just like a lie'
"Straighten up and fly right"

[Adrian Caspersz]

On 21/04/2021 17:30, Theo wrote:
> Deloptes <delo...@gmail.com> wrote:
>> bob prohaska wrote:
>>
>>> 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.

>

> 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.

There is also this portable kit for £28.86 from Amazon. Could be junk,
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

[Deloptes]

Theo wrote:

> 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.

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.

[Martin Gregorie]

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

[Joe]

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

[Computer Nerd Kev]

bob prohaska <b...@www.zefox.net> wrote:
> 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.

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.

--
__ __
#_ < |\| |< _#

[Martin Gregorie]

On Wed, 21 Apr 2021 23:25:23 +0000, Computer Nerd Kev wrote:

> 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.
>

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.

[bob prohaska]

Martin Gregorie <mar...@mydomain.invalid> wrote:
>
> I suspect you'll get better suggestions if you can outline what you are
> trying to do.

My hope was to elicit reports of practical experience....

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

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.

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

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

Thanks for writing!

bob prohaska

[bob prohaska]

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

[bob prohaska]

Computer Nerd Kev <n...@telling.you.invalid> wrote:
> bob prohaska <b...@www.zefox.net> wrote:
>> 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.
>
> 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.
>

Ok, that's a good hint. I'm looking at something like:
https://www.amazon.com/DIGITNOW-Capture-Grabber-Cassette-Converter/dp/B079CBGDST/ref=pd_rhf_dp_p_img_2?_encoding=UTF8&psc=1&refRID=YV3EVDFX4FWZF58TY2CW
There are reviews saying it works with Raspberry Pi, so maybe it'll work
with xoscope. It doesn't have to be good, just good enough to catch
sags and spikes on a timescale of milliseconds.

> 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
>

Thank you for the link!

> 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.
>

I'm experienced with analog 'scopes and don't want one. They aren't
useful for catching one-off transient events, which is what I'm looking
for. Something with a stop trigger is essential. A freestanding DSO
would be nice, but I won't use it enough to justify the cost and storage.

[Ahem A Rivet's Shot]

On Wed, 21 Apr 2021 03:05:36 -0000 (UTC)
bob prohaska <b...@www.zefox.net> wrote:

> 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.

A search for raspberry pi DSO revealed a range of devices called
bitscope which (if as good as advertised) look like handy devices, probably
overkill for what you want but it would have cleared several feet of bench
space in my 1980s labs.

--
Steve O'Hara-Smith | Directable Mirror Arrays
C:\>WIN | A better way to focus the sun
The computer obeys and wins. | licences available see
You lose and Bill collects. | http://www.sohara.org/

[Folderol]

On Thu, 22 Apr 2021 07:26:28 +0100
Ahem A Rivet's Shot <ste...@eircom.net> wrote:

>On Wed, 21 Apr 2021 03:05:36 -0000 (UTC)
>bob prohaska <b...@www.zefox.net> wrote:
>
>> 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.
>
> A search for raspberry pi DSO revealed a range of devices called
>bitscope which (if as good as advertised) look like handy devices, probably
>overkill for what you want but it would have cleared several feet of bench
>space in my 1980s labs.
>

Bitscope are expensive for what they are, and not actually very good (you
won't see transients at all). I get *far* better results with an ancient Scopex.

--
W J G

[me]

A little more expensive, but not much

https://espotek.com/labrador/product/espotek-labrador-board/

may be worth a look - its (very) small, fully open source software and
while I had a different use case, worked for me. Looking at the web
site, I probably ought to update my software version before I use it
again.

MArtin

On Thu, 22 Apr 2021 05:30:55 -0000 (UTC), bob prohaska
<b...@www.zefox.net> wrote:

>Computer Nerd Kev <n...@telling.you.invalid> wrote:
>> bob prohaska <b...@www.zefox.net> wrote:
>>> 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.
>>
>> 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.
>>
>Ok, that's a good hint. I'm looking at something like:
>https://www.amazon.com/DIGITNOW-Capture-Grabber-Cassette-Converter/dp/B079CBGDST/ref=pd_rhf_dp_p_img_2?_encoding=UTF8&psc=1&refRID=YV3EVDFX4FWZF58TY2CW
>There are reviews saying it works with Raspberry Pi, so maybe it'll work
>with xoscope. It doesn't have to be good, just good enough to catch
>sags and spikes on a timescale of milliseconds.
>

<snip>

[Joe]

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

[Ahem A Rivet's Shot]

Thank you - so not as good as advertised then - pity.

[The Natural Philosopher]

On 21/04/2021 18:15, Adrian Caspersz wrote:
> On 21/04/2021 17:30, Theo wrote:
>> Deloptes <delo...@gmail.com> wrote:
>>> bob prohaska wrote:
>>>
>>>> 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.
>
>>
>> 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.
>
> There is also this portable kit for £28.86 from Amazon. Could be junk,
> not built mine yet (too much trigger happy shopping, it's sat on a shelf).
>

you can buy a second hand real scope for not much more...

> 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
>


--

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

Herbert Spencer

[ray]

Please forgive my ignorance on the topic, but would it be possible to
use another PI with 'duino type device? Seems the duino would do the
sampling and relay the results to the other PI.

[Martin Gregorie]

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.

[Theo]

ray <r...@zianet.com> wrote:
> Please forgive my ignorance on the topic, but would it be possible to
> use another PI with 'duino type device? Seems the duino would do the
> sampling and relay the results to the other PI.

You can do that kind of thing, but you're limited by the sample rates and
input range of the microcontroller, and also by the output bandwidth. For
example you could make something to sample via an ADC pin and squirt out
over SPI, but you need to worry about not dropping samples because the
output is busy, and you also won't see any voltage that's too low or too
high. For example in a power supply situation you might be worried about
negative voltages or spikes above the power rails, which the ADC won't
capture. Also the ADC resolution is typically low if you're running at high
speeds. This is where a proper scope comes in handy.

If it's all you have and you don't have major demands, by all means give it
a try.

Theo

[David Higton]

In message <20210421212...@jresid.jretrading.com>

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

[bob prohaska]

Joe <j...@jretrading.com> wrote:
>
> 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.
>

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?

[bob prohaska]

ray <r...@zianet.com> wrote:
>
> Please forgive my ignorance on the topic, but would it be possible to
> use another PI with 'duino type device? Seems the duino would do the
> sampling and relay the results to the other PI.

That would work, but it's a bit more work than I wanted to tackle.
I'm no programmer, by any stretch, and making front ends for A/D
coverters isn't entirely simple, either. A sound capture device
contains at least anti-aliasing filters, I'll have to add only
attenuators.

At the moment the Hantek 6022 is looking rather promising.

The openhantek software compiled easily on the Pi4, but it
won't run demo mode for some reason. I'd like to get a look
at that before buying hardware.

[Joe]

[Joe]

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

[Computer Nerd Kev]

bob prohaska <b...@www.zefox.net> wrote:
> Computer Nerd Kev <n...@telling.you.invalid> wrote:
>> bob prohaska <b...@www.zefox.net> wrote:
>>> 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.
>>
>> 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.
>>
> Ok, that's a good hint. I'm looking at something like:
> https://www.amazon.com/DIGITNOW-Capture-Grabber-Cassette-Converter/dp/B079CBGDST/ref=pd_rhf_dp_p_img_2?_encoding=UTF8&psc=1&refRID=YV3EVDFX4FWZF58TY2CW
> There are reviews saying it works with Raspberry Pi, so maybe it'll work
> with xoscope.

Xoscope just listens in on the audio stream, so if other ALSA audio
programs work, it will too.

These sorts of adapters are cheaper and also work on the Pi (I've
used one the same as this, but only the audio output):
https://www.ebay.com/itm/303879860060

It even works on a old Linux installation via OSS (again only
tested output).

>> 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.
>
> I'm experienced with analog 'scopes and don't want one. They aren't
> useful for catching one-off transient events, which is what I'm looking
> for. Something with a stop trigger is essential. A freestanding DSO
> would be nice, but I won't use it enough to justify the cost and storage.

Fair enough, your power supply monitoring is more of a data logging
application anyway. Possibly the slowest speed setting on a CRO
combined with a video recording of the screen would work. You'd
need to have all the settings worked out fairly well though and
that would be a hurdle for a first-timer.

[Gerhard Reithofer]

On Wed, 21 Apr 2021, bob prohaska wrote:

> 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.

One from bitscope?
https://www.bitscope.com/

My operational area was protocol analyzing and the smallest (micro)
worked well for me.

--
Gerhard Reithofer - Techn. EDV Reithofer - http://www.tech-edv.co.at

[bob prohaska]

Computer Nerd Kev <n...@telling.you.invalid> wrote:
> bob prohaska <b...@www.zefox.net> wrote:
>> Computer Nerd Kev <n...@telling.you.invalid> wrote:
>>> bob prohaska <b...@www.zefox.net> wrote:
>>>> 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.
>>>
>>> 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.
>>>
>> Ok, that's a good hint. I'm looking at something like:
>> https://www.amazon.com/DIGITNOW-Capture-Grabber-Cassette-Converter/dp/B079CBGDST/ref=pd_rhf_dp_p_img_2?_encoding=UTF8&psc=1&refRID=YV3EVDFX4FWZF58TY2CW
>> There are reviews saying it works with Raspberry Pi, so maybe it'll work
>> with xoscope.
>
> Xoscope just listens in on the audio stream, so if other ALSA audio
> programs work, it will too.
>

Just got the DIGITNOW audio capture device. Audacity finds it without
trouble and displays AC hum on the VU bargraph, so I'm pretty sure
the hardware works. Dmesg reports
[2795922.290892] hid-generic 0003:2034:0105.000A: input,hidraw3: USB HID v1.00 Device [Generic USB Microphone] on usb-0000:01:00.0-1.4/input2

and lsusb -t reports

/: Bus 02.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/4p, 5000M
|__ Port 1: Dev 2, If 0, Class=Mass Storage, Driver=uas, 5000M
/: Bus 01.Port 1: Dev 1, Class=root_hub, Driver=xhci_hcd/1p, 480M
|__ Port 1: Dev 2, If 0, Class=Hub, Driver=hub/4p, 480M
|__ Port 3: Dev 3, If 0, Class=Hub, Driver=hub/3p, 12M
|__ Port 1: Dev 5, If 0, Class=Human Interface Device, Driver=usbhid, 12M
|__ Port 1: Dev 5, If 1, Class=Human Interface Device, Driver=usbhid, 12M
|__ Port 2: Dev 6, If 0, Class=Human Interface Device, Driver=usbhid, 1.5M
|__ Port 4: Dev 9, If 1, Class=Audio, Driver=snd-usb-audio, 12M
|__ Port 4: Dev 9, If 2, Class=Human Interface Device, Driver=usbhid, 12M
|__ Port 4: Dev 9, If 0, Class=Audio, Driver=snd-usb-audio, 12M

The device file corresponding to the sound capture device is /dev/hidraw3

However, xoscope looks for signal at /dev/comedi0, which isn't created.
There's a dialog box which seems to invite device selection, but the
only choices are NONE and COMEDI.

If I try something like
sudo xoscope hidraw3
xoscope runs but says it can't read hidraw3.

It looks as if I'm either bungling the commandline syntax or the device filename.
Or, maybe some intermediate software is required. Comedi manpages are present, but
there don't seem to be any related executables.

If anybody's got a hint please post!

[Computer Nerd Kev]

From the README:

"* You will need (optionally?) the ALSA and COMEDI libraries. If
any (or all) of these libraries are absent, xoscope will build
without that library's input capability.?"

If you compiled it yourself, maybe it didn't find the ALSA library
on your system and built without ALSA support? If you didn't
compile it yourself, well maybe you should...

> If I try something like
> sudo xoscope hidraw3
> xoscope runs but says it can't read hidraw3.
>
> It looks as if I'm either bungling the commandline syntax or the device filename.
> Or, maybe some intermediate software is required. Comedi manpages are present, but
> there don't seem to be any related executables.

"xoscope -h" should display the available options, "-A" is supposed
to select the ALSA sound device (default is "default" - I'm not
sure whether ALSA always automatically sets a "default" sound
device).