!USBScopePlus and !USBAudioProbe

Two new USB Audio programs are now available from

http://www.audiomisc.co.uk/software/index.html

Links to them can be found in the USB Audio section of the webpage.

!USBScopePlus is an extension of !USBScope. It adds the ability to output
various types of user-controlled test waveforms to the Scope + FFT spectrum
analysis, etc, facilities. Thus it can be used as a ‘test bench’ for
checking audio equipment. It is capable of providing ‘measurement lab’
quality results given the use of suitable USB Audio ADC/DACs.

!USBAudioProbe scans the computer system and lists the details of any USB
Audio devices it finds. This lets the user discover what abilities their
setup may support. Hence it is useful to determine what sample rates, etc,
they can employ when using the other USB Audio programs.

Note that, alas, not all RO systems currently support USB Audio.

Jim Lesurf

For info. Colin G. has said I can report this in case it helps others:

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Just to report it works OK on a Rpi 400. Dacmagic Plus playing 192kHz/24bit with IsocPlayer into a UCA202 and recording with IsocRecorder or with either USBScope or USBScopePlus running. Had to make sure the UCA202 was plugged in after IsocPlayer started playing.

Thanks, Chris. :-) Your feedback raises two points I can add that may help others.

1) At present !USBScopePlus can’t play out via a Class 1 DAC (although other relevant programs can). Intend to add this soon.

2) The ‘order’ in which devices are found by a scan of the USB connections can matter as !USBScopePlus and some others find and use the ‘first one they can find’ when they need to use a DAC or ADC. This saves the user having to specify in some way, so automates the process. But if you have, say the DAC Magic Plus and the UCA202 it will choose the first of them it finds listed to use as a DAC.

Also, my programs include source code and people can see how it used Colin G.‘s new access library to make use of USB Audio easier for programmers. Given that I’m a dummy when it comes to programming, if I can do this sort of thing, others can clearly do far better. :-)

Update. I’ve been experimenting with a UCA202 as my ‘test’ for adding the ability to symultaneously playout and capture using a Class 1 device. Finally got this going correctly. I was ‘confused’ for a while by the unxpected use it makes of a ‘monitor’ switch and gain control. It also has single channel and other ‘low’ modes that could also confuse use. So I modified the setup to ignore these and go for 2byte stereo.

I want to add the feature of a ‘user defined waveform’ to the tone playout. Once that is done and works I’ll release the new version.

I’ve now updated the version of !USBScopePlus available from the page at

http://www.audiomisc.co.uk/software/index.html

Version 1.00 can now use 16bit Class 1 DACs and ADCs, albeit with lower performance than the 24bit Class 2 ones. It also now offers the user the ability to define their own waveform to be played as the test tone.

Does your software work with USB to oscillscope hardware?

I’m not sure what you are asking. !USBScopePlus allows a suitable RO system to become a combination of an oscilloscope, FFT spectrum analyser, and test signal generator. So when I use it with, say, my ARMX6 and a 2i2 I can have both a sig gen and a 2-channel scope with a 96kHz bandwidth. (Limits set by the 2i2.)

This shows a screengrab (earlier version, so the current one shows more)
http://jcgl.orpheusweb.co.uk/temp/Probe_SQ.png
That shows the generated tone being measured, example being a band-limited squarewave. If you change the ‘SQ’ to ‘SW’ you can see an example where the output test tone is a sinewave.

The new version also works with cheaper USB devices like the UCA202, but then has lower resolution and bandwidth – because of the choice of USB device.

What “USB to oscilloscope hardware” do you mean?

Something like ‘Picotech.com’

Or is that something different.

[edit]

‘Like’ in the sense that the computer can read in digital samples, etc. But the transfer processes will differ.

!USBScopePlus uses the transfer methods provided for USB Audio devices compliant with the relevant defined ‘USB Audio Classes 1 or 2’ methods/protocols.

I expect Pico do something rather different as their sample rates are, IIUC, far higher. Don’t know if they can do 24 bit samples, though. Many ‘digital scopes’ tend to be 8bit or 16bit. Their advantage is high rates and high bandiwdths, not precision unless you pay up!

And with !USBScopePlus the user has a choice of maker of the hardware they use for the ADC / DAC. I’ve (mainly) been using the Focusrite 2i2 ‘3rd Gen’ as it works very well, and is popular for audio uses. But any stereo (i.e. 2 channel) class compliant device should work. That said, I’ve not checked ones that are cheap and only run at rates well below 44.1k.

What “USB to oscilloscope hardware” do you mean?

Presumably what you get when you google for “USB oscilloscope”. I.e. less bits, more bandwidth, for electronics use – vastly higher frequencies than the audio stuff. 100 MHz or more bandwidth, dual or quad channel, possibly including a multi-channel logic analyser.

The electronics guys usually refer to an audio signal as “direct current” IIRC :-)

Not the ones at the BBC who work for R3. :-)

But yes, the tendency for the ‘USB oscilloscopes’ is to go for bandwidth and number of channels, not precision in terms of bits-per-sample. You can get some interesting exceptions, though. I do have a FUNCubeProPlus SDR that sends its output as 16bit USB Audio and it works up to a couple of GHz. But with a narrow bandwidth. I;d love to do a scope for that for RO as I did for Linux. But the control side is, I think, not available for RO. Maybe I should ask people about that…

I have a bottom-of-the-range Picoscope. Up to 100 MSa/s, 2 channels, serial decoding, arbitrary waveform generator… much more general purpose than Jim’s, which is specifically for audio. Excellent value for money. I can recommend it (I have no connection with Picotech). They also do others with higher sampling rates, more channels, etc.

FWIW I’d love to get the ADALM-PLUTO as well as the FUNCube working with RO as between them they can do most things up to about 6 GHz. :-) The problem is the command interface via USB which I’m sure wouldn’t work as things stand. But given that I could do something similar to the !USBAudioProb for RF.

Just to add that a new version of !USBScopePlus – Version 1.01 – is
now available via

http://www.audiomisc.co.uk/software/index.html

This differs from the previous versions only wrt using the current USB
Audio Library version. So it is functionally the same as Version 1.00. But
uses the up-to-date library created by Colin Granville. This can be found
at http://ftpc.iconbar.com/usb/index.html