Low-Cost USB Oscilloscope

[PJALM]

Here is a very simple one I found that uses a 18F4550.

http://ostry.w.szu.pl/miniscope.php?lang=en

They also have some more complex models as well but this one includes everything and its free.

[malc-c]

Here is a very simple one I found that uses a 18F4550.

http://ostry.w.szu.pl/miniscope.php?lang=en

They also have some more complex models as well but this one includes everything and its free.

OK downloaded the exe, browsed the files etc... but there is no scematic. It states on the website

Project of digital storage oscilloscope, hardware is just PIC18F4550 and few passive components.

Browsing the site there is an updated miniscope2 which shows a PCB which has a bit more than a few descrete components but the chips look too small to be a 18F4550 (assuming its a 40 pin device)



Do you still have the schematic and can you post it here or provide a link to where it can be downloaded from ?

EDIT - just re-read the bit about the ver2 -Based on AT91SAM7S64 microcontroller. - Doh !

[T.Jackson]

Here is a very simple one I found that uses a 18F4550.

http://ostry.w.szu.pl/miniscope.php?lang=en

They also have some more complex models as well but this one includes everything and its free.

Hi

The sample rate of 25kSPS won't allow for much. Won't even cover the audio spectrum. (25kSPS / 10) = 2.5KHz. For some half-decent performance, at least half a dozen or so chips are required. Analog front-end using an OPAMP, discrete ADC (at least capable of 2MSP/s), SRAM - 32KB, address counter IC, micro controller to shuffle the sampled data to the host - (PC in this case), calibrated time base’s - micro controller won't be fast enough to set sample rate or address the SRAM. Big job to come up with some decent goods. Doubt I’ll bother if I can’t get at least 1MHz of solid bandwidth.

Best Regards,

Trent Jackson

[T.Jackson]

Using a PIC18f4550 @40MHz and an analog front-end - here's my calculated guess at what to expect if things are done right. Internal ADC conversion time: (2 - 3) uS, assuming a source impedance < 200 ohms. 1 / say 2.5uS = 250kSP/S Allow most of the internal RAM for buffering. 2KB? Time taken to fill RAM? At least a few cycles. Knock off say another (2 - 3) uS from the sample rate?. At best, very best - my guess is something like 100kSP/S. Useable bandwidth of about 10KHz without any software magic in the Windows UI.

However, I reckon the author of Bitscope would manage to squeeze about (200 - 300) Khz out of this arrangement...

Here's how I think he does it: (waveform is all there but scattered)

1. Fill RAM with samples (using fastest time base.)
2. Retrieve samples from RAM & send to PC.
3. Buffer samples.
4. Analyze / sort samples (not too sure of the algorithm.)
5. Render and apply anti-aliasing to waveform.

With step 4 it might be as simple as looking for consistencies of samples and ignoring them. But what I do know for sure is that it works because the waveform is actually all there, but it’s scattered. Parts of it might be in the first few hundred samples while the rest of it might be residing in the last few thousand.

Am I kind of on the right path?, anyone care to add?

Best regards,

Trent Jackson

[T.Jackson]

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

[mister_e]

maybe i have some eyes problem... but it use a 12F675 which make it, by far, more impressive...

Amazing what we can do with ONLY 1K of code and a 8 pin PIC...

[T.Jackson]

Right you are. It's uses a 12f675. I think I must be the one with an eye problem. All round very impressive indeed.

Trent Jackson

[peu]

did you guys saw this one: http://www.semifluid.com/?cat=9 ?


Pablo