I have been playing with USB using Ztex's USB module. I plan to make an oscilloscope and function generator.
Therefore I would need an AD and DA chip with 12 bit resolution. And quite fast ones also. Plus I can't really handle the surface mounted ones yet, so DIP would be good or a break out board with DIP pins. Could someone please point me in the right direction.
Then other stupid question. If I have understood right a AD chip only handles single polarity of signal. I ques I need an op amp to convert from dual polarity to single polarity - or what? Are there any example schematics in the net. I will try with google but if someone can point me to one - thanks.
How about DA How can I output dual polarity signals with it? Op-Amp again?
Sorry for stupid questions....
Best Regards Kari
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PICs, Displays,Relays - USB-SPI-I2C http://www.byvac.com
USB and FPGA boards http://www.ztex.de
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I suggest that you subscribe to Circuit Cellar and/or Nuts and Volts. Start reading the articles, and use your subscriberhood to go through the archives. A USB O-scope is such an obvious project, it has to have been done.
I think this might be a pretty difficult project, if you are not already familiar with high-speed A/D/A stuff. A lower-speed (audio) scope is a much easier project because you can modify an existing sound card to get DC response. I recommend a cheap USB sound device for this purpose.
Complete schematics, board layouts, photos, and discussion at "Sound Card DC Input Modification".
The unit I show there is fairly easy to work on, and there is room inside the metal case for the small circuit you need to add. Connections are made to the main circuit board at easy-to-find locations, and don't require any surface-mount work. For example, the existing inputs are AC coupled through small can electrolytics with through-holes, not surface mount chips (like other USB sound devices I've worked on), so you can easily clip them out and solder to the leads.
Since you already own Daqarta, the other beauty of using a sound card is that it already works with the software you've got. Even if you were planning to use another software package, using a sound card would still be a powerful advantage over writing your own code.
If you need higher sample rates than 48000 Hz, this cheap USB device won't do the job. There are cards that sample at
192000 Hz, but if you want MHz ranges this approach won't work. But then, at MHz ranges constructing a homebrew circuit would not be for the faint of heart... better to buy a cheap hardware benchtop unit.
Just my 2 cent's worth...
Best regards,
Bob Masta DAQARTA v6.00 Data AcQuisition And Real-Time Analysis
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Scope, Spectrum, Spectrogram, Sound Level Meter Frequency Counter, FREE Signal Generator Pitch Track, Pitch-to-MIDI Science with your sound card!
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