Re: Low spec 'scope.

On a sunny day (Fri, 30 Aug 2024 06:36:07 -0000 (UTC)) it happened Jasen Betts
<usenet@revmaps.no-ip.org> wrote in <varp8n$1bcop$1@gonzo.revmaps.no-ip.org>:

On 2024-08-29, Don Y <blockedofcourse@foo.invalid> wrote:

On 8/29/2024 1:57 AM, Jasen Betts wrote:

On 2024-08-28, Don Y <blockedofcourse@foo.invalid> wrote:

On 8/28/2024 7:47 AM, Martin Brown wrote:

On 28/08/2024 08:39, Liz Tuddenham wrote:

The recent thread on high-end oscilloscopes has reminded me of a project
that I shelved some years ago and might be due for resurrection:  I am
looking for a real-time display about 3" x 4" that can behave as an X-Y
oscilloscope with a bandwidth of about 100 Kc/s; a flat panel would be
ideal.
>
Currently I am using an actual X-Y oscillocsope to monitor the output
from a stereo gramophone cartridge, which allows me to check historic
discs for damage or faulty recording geometry.  The tube is about 14"
long, which means it has to be a standalone shelf unit and I can't build
anything like it into portable equipment.

>
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.

 
or any other sound card scope software,

>
I think the OP wants a "real-time" X-Y display.  If it is acceptable to
treat this as a two-step process -- acquire data, display -- then
it becomes a lot easier to implement.

>
I think few millisecods latency will go unnoticed,
>

Does it *simultaneously* sample each channel?  Or, toggle between them?

 
It makes an audio recording using commodity PC sound hardware.
https://www.ti.com/product/PCM2900C has 2 ADC channels

>
But, is that true of ALL "sound cards".

>
That is not important, avoid unsuitable devices.
>

The advantage would be that you could locate the data acquisition
hardware separately from the (COTS) display.

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

>
The OP seems to want to avoid writing any code.  And, to be fair, capturing
two 100KHz signals and pushing them onto a display while ERASING any previous
display content is a bit of a job, especially if you want to truly mimic
a 'scope in X-Y mode (where the display's persistence allows some portion
of "old" traces to remain visible before fading away (with the LCD, the
software would have to perform that function)

>

(think about how you would decide *what* to erase, given that a particular
pixel may have been painted as part of N consecutive cycles -- even if it
is the "oldest" pixel in a time-sorted list)

>
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.

OP wants to see needle movement
High speed camera and play back at any speed.
Smartphone?
I think mine has a high speed mode, but a bit more speed you should be able to get for a few dollars?