Low-Cost USB Oscilloscope
Hi everyone.
In terms of actual hardware circuitry, I would like to invite you all to share your views on what just exactly would be required in order to produce a respectable USB-based Digital Storage Oscilloscope. My first initial thought is a 18f4550 teamed up with a fast dedicated ADC and 32K of SRAM. Plus, an analog front-end of some description somewhere in the equation. Is there an easier way or some form of hidden magic inside a 18f4550 or similar? Anyone accomplished a project like this?
Desirable criteria:
1. 5 MHz bandwidth.
2. Dual Trace.
3. 400V.
4. All controls adjustable via Windows XP GUI.
5. Low-cost, compact size.
Regards,
Trent Jackson
If it's under $1,000 it's a toy!
Quote:
Originally Posted by
Luciano
Hi,
You need a microcontroller with an external memory bus.
Even with an external memory bus, the oscilloscope will be
slow or better said just a toy. My assumption here is
that you need an oscilloscope for projects where
microcontrollers are involved. If you need an oscilloscope
for audio signals then go ahead, it will be fast enough.
Try to calculate how fast your oscilloscope could be.
Best regards,
Luciano
For the hobby end user, most test gear is a toy. In my opinion even Bitscope falls into this category. It's not uncommon nowadays for service techs to be using 500MHz + DSOs. Of course an extreme overkill for any enthusiast and not something that you would ever really consider unless there was some considerable financial gain to be made from it from either generating new work or speeding up the process of your current service. If you don’t work with 500MHz gear then chances are you don’t need it.
SRAM: 20nS or thereabout
ADC: 40MSP/s
The upper limitation is the RAM. (1 / 20nS) = 50MSP/s
*Anything greater than this is like trying to generate free power. Or, more commonly an amplifier that supposedly puts out 200WRMS when the DC rails are only good for 100W. Like duh, did I just get ripped off or what…
*The million dollar question I guess is this. Without using too much black magic in the software for interlacing and periodical guess work, how many samples of a waveform is considered to be sufficient analysis? Sure with 40MSP/s you could take one sample of a 40MHz sine wave every second. Won’t look like much of a sine wave on the screen though. If you allowed say 20 samples of every cycle then this might suffice. (40MSP/s / 20) = 2 MHz. Undoubtedly there must be the presence of some host software magic some where a long the line. Hmm, is my DSO really 20MHz or is there just a whole heap of black magic in the software making a lot of assumptions?
Best Regards,
Trent Jackson
Top link: µScope using 16f675
This is real good. This guy has used a PIC 16f675 to make a fully self-contained CRO. For about $5 you can build this thing that simply just plugs into any spare composite video in on your TV. Bandwidth is only a few KHz, but for $5 could you really complain?
Even more notable is that he has also reinvented the game Pong using nothing more than a 16f675!
(*Very scary)
http://members.chello.nl/r.dekker49/.../uscope_e.html
Best Regards,
Trent Jackson