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Hands-on - A digital oscilloscope
Let's build a simple digital oscilloscope.
- Single channel, about 100 MSPS (mega-samples-per-second)
- RS-232 based (we'll look into USB too)
- Inexpensive!
A simple digital oscilloscope recipe
Using parts from KNJN.com, here are the basic items of our recipe.
Here's how they look.
![](images/FlashyHands-on/Flashy_PlutoKit_labels.jpg)
We also need the following (these are common items, hopefully available in many people's lab).
- A small DC adapter 5V to 9V, 100mA or more.
- An RS-232 extension cable.
- A little screwdriver.
- And of course, an oscilloscope probe.
![](images/FlashyHands-on/Flashy_MiscParts.jpg)
Now let's put things together.
1. Pluto
The male connector needs to be soldered on Pluto.
Let's also screw-in the two standoffs.
![](images/FlashyHands-on/Flashy_PlutoConnector.jpg)
2. Flash
Now for Flash. The female connector goes on Flash's bottom. Place it and solder it there.
![](images/FlashyHands-on/Flashy_FlashBottomConnector.jpg)
The BNC goes on Flash's top.
Let's make sure the BNC signal and ground leads go into the right spots.
![](images/FlashyHands-on/Flashy_FlashBNC.jpg)
Then return the board to solder the BNC.
3. Pluto and Flash combo
With the connectors soldered, the two boards mate easily, and the top standoff screws can be added.
![](images/FlashyHands-on/Flashy_PlutoFlashyCombo.jpg)
4. Let's power it up
Now TXDI can be connected to Pluto.
We add the RS-232 connection to a PC, the 9V (or so) power adapter, and the oscilloscope probe on the BNC.
![](images/FlashyHands-on/Flashy_PlutoFlashTXDI.jpg)
We are ready to probe!
5. The software
Let's run the Flash software provided with Pluto.
First we get a flat trace.
![](images/FlashyHands-on/Flashy_Software.gif)
Let's probe something.
We fire up our signal generator, select triangular signal, here it is!
![](images/FlashyHands-on/Flashy_SoftwareTrace.gif)
6. Possible improvements
Here are a few ideas:
- Use a Pluto-II instead of a Pluto (Pluto-II has a boot-PROM so can be active at power-up, and the bigger FPGA allows more features in the oscilloscope). Or even a Pluto-3 and a FlashyD to get a two channels oscilloscope. Or use a different Flashy revision - for example rev. K allows precise frequency measurements and equivalent-time sampling.
- Make the oscilloscope USB-based (see here) or use a Saxo or Xylo board instead of a Pluto (which are natively USB controlled/USB-powered, and support FlashyD = two channels).
- Another possibility is to add an LCD (like KNJN item#5300) but don't use a Pluto FPGA board in this case (it wouldn't work because its FPGA is too small to drive the LCD while the oscilloscope is running).
That's it. Your turn to experiment!