Low spec 'scope.

How about this?

That's the sort of thing, but it does need a 'Y' input and must start in the correct mode on power-up, as the screen will be built into a piece of equipment with no room for extra panel controls.

Thanks very much for that. It has most of the reatures I need and the sampling rate is just about adequate. It 'remembers' its last settings, which is essential for this application.

I have coded in the past but it was a most frustrating exercise and something I would like to avoid if possible. Also, I don't have any way of connecting to the chip and uploading the code.

Very reasonable

The detail is extemenly important in this application - the minimum resolution being 200 dpi.

I'll have to work through them and see which ones can be used as X-Y scopes, with good enough resolution and the ability to start fully functional from power-up.

Failing that, I have an oscilloscope tube and driver chassis, so I could mount it horizontally in the bottom of the box with a 45-degree mirror, so I can look down on it through a hole in the horizontal control panel.

I think that Daqarta software can probably do about what you want using the PC stereo soundcard to digitise X & Y. 100kHz bandwidth might be pushing it but it should be fine for audio up to 20kHz.

I have used it for various demos. The spectrogram is handy too. Even if you decide it isn't for you the free signal generator continues to work.

I have never looked hard enough or at a high enough frequency to tell the difference. Audio demo's work best around 440Hz orchestral A which most people can hear well. Waveform shapes and sounds are fun demos.

The guy knows what he is doing so I expect it is simultaneous sampling of the waveforms to within a few memory cycles. Skew only becoming a problem at very high frequencies. It is cute there is a free trial period and you get to keep the (audio) waveform generator.

There is something similar for Android tablet/phones too but I don't think that one does X-Y Lissajous figures (I could be wrong about that). The waterfall spectrograph is quite a handy toy to have on your phone...

It is a neat piece of software. Every now and then AV codes take against it because it does do a bit of rather low level IO access (obviously).

or any other sound card scope software,

It makes an audio recording using commodity PC sound hardware.

It's starting to feel like raspberry pi + LCD display + usb sound card.

That would correspond to a screen 1.6" x 1.2" at 200 dpi, which would be a bit too small. I would regard 3" x 4" to be the optimum size. and 600 x 800 pixels to be the absolute minimum. There is no need for colour.

I'm not trying to display 2 channels on 1. I need an X-Y display so that I can see the angle of contact of a stereo stylus with the roughness of the groove wall and the pattern it traces as it plays the modulation.

seventies) in electronics.

I have programmed in Z80 machine code, Algol, Basic, Applescript, PHP and HTML, but have only used the last two recently. I also don't have any programming tools as all my designs are analogue.

Not really, I need to know the instantaneous vector direction of the stylus movement. On some 'Mono' recordings it can actually be moving in a circle (the groove modulation is helical).

~~~~~~ Detailed technical information ~~~~~ This is caused by the cutting face of the recording cutter not being at right angles to the direction of the groove (sometimes done deliberately to throw the swarf clear), which results in the modulations on the two groove walls being out of step with each other. When played with an elliptical stylus tip, the phase difference generates a vertical component which muddies the mono sound and plays hell with a declicker. Twisting the cartridge about a vertical axis will displace the contact points of the stylus on the groove wall and restore the sound quality The amount of twist needed will depend on the amount and direction of misaligment of the cutter, the groove wall angle and the size of stylus used for playback. The pattern on the X-Y 'scope gives me valuable information about this effect and enables me to optimaise the playback angles without a lot of trial and error.

~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~

When playing 'shellac' records (which contain a lot of abrasive) the roughness on one groove wall displaces the stylus at an angle up and down the slope of the opposite groove wall. On an X-Y display, without any modulation this looks like a letter 'X' but the angles of the two arms of the 'X' may not be at 45 degrees.and may be unequal or even change as the record revolves. I am dealing with material that may have been badly recorded and will almost certainly have been damaged by poor storage and massive playback devices (with heavy resonances). The 'scope is there to enable me to identify and correct as many of the defects as possible.

There seem to be quite a few to choose from - and I have a couple complete with their chassis in the attic. It looks as though I am going to be short of space in the equipment I am designing, so perhaps the oscilloscope will have to go as a separate item anyway.

That's what a friend keeps telling me. He advocates even the simplest jobs being done with a microprocessor - but then he never seems to produce anything that works. At least yours appear to be built and working.

I think few millisecods latency will go unnoticed,

That is not important, avoid unsuitable devices.

store a ring buffer of pixel coordinates and a raster size buffer of pixel birthdays and then the update process becomes O(1)

look up the age(th) pixel in the buffer, if the age in the birthday map is wrong then it has since been overwrittenm, so do nothing, else dim it a little.

this won't get you anti-aliasing, which is possibly more valuable,

Maybe there's a way to get both subpixel resolution and a fading effect. perhaps some sort of palette rotation? does it actually need a microcontroller? perhaps do the whole thing in an FPGA.