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converting my computer to an oscilloscope using usb port

by unwana / February 13, 2006 3:34 AM PST

Before getting my computer to work as an oscilloscope, I need to design some sort of input hardware that will serve as a source of analogue signal to my usb port. I need a simple design (schematics)that can serve as a probe to the usb port and a corresponding device driver.I am also stuck on how to write a software program in matlab to interprete these input signals to graphs on my computer.
please could you assist or refer me to any project on this subject. Thanks.

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Did this back in college, but that's 15 years ago
by kschang / February 14, 2006 2:45 PM PST

Back then state of the art is 486/Pentium, and we were still using ISA slots. We actually build a circuit board that plugs into the ISA slot, with 2 A2D converters for the X and Y channels. My partner and I, that is. Actually, he did all the hardware and I did all the software. I was able to basically scan a bunch of values into an array, look for a zero point, and use that as a start so the waveform doesn't wander all over the place. It was written in Turbo Pascal (i.e. Delphi's predecessor), none of your fancy-shmancy "Matlab" stuff nowadays. Grin 2 channels can be displayed independently, or combined in an XY graph, with scaling, different timing, offsets, and all that. Grin

We actually got the circuit diagram off the Internet, which gave us a starting point. Though we VASTLy underestimated the speed of the PC needed.

I would actually advise you NOT to use USB, unless you want to learn how to build an USB device as well. Keep it simple, use good old fashioned SERIAL port. Plenty of existing code that'll read serial ports in almost any programming language.

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how convert as a oscilloscpe
by qibtiah / February 20, 2012 5:04 PM PST

i also want to know how to make connection between pc and input...i need some idea

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Re: connection
by Kees_B Forum moderator / February 20, 2012 5:22 PM PST

Once you've selected an input port type to (USB 2, USB 3, serial port, parallel port, Bluetooth, IR) all you need to buy or design is the hardware that sends the signal (it has to know the protocol and handshaking used) and the program that reads and processes the signal. A driver for all those port types I mentioned already is included in the OS.
It's different if you decide to design and build your own PCI card with a custom interface. Then you have to do all three things (hardware to send the signal, hardware to receive the signal, driver to 'run' that PCI card) yourself. Then the first thing to decide is if you want to do it In Windows or in Linux.

One possible problem: the frequency of the signal. Assuming you need 100 measurements in one cycle to draw a nice graph, a 10 Mhz signal needs 1 billion measurements a second. No interface is that fast.

You mention "analogue signal to my USB port". That can't be done. USB (like all these interfaces) are digital. So you would need an A/D converter whatever you do.

Best of luck with your project.

Kees

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