This is a very simple design of digital oscilloscope. The original project comes from EP 8/2004. The only difference I've made was adding RS232 to USB converter to use it with my laptop. Schematic can by found here: analogue and digital.
There can be seen analogue input section with OPA2350 amplifiers and relays as voltage dividers. ADC is fast television IC, TDA8703. Digital data goes through DS89C420, via USB to PC application showing results.
On the other side we can see lots of addicional tuning SMD components. Making the analogue section work properly was a really hard work, especially with a variety of input frequencies, amplitudes and shapes.
It is harder and harder to find RS232 connector in modern computers. That's why I decided to make this converter. I doubt there is at least one computer without USB. Schematic of USB section can be found here.
Another adventage of this board is a place for separate power supply as the device can't be powered from USB plug. My aim was to separate it from the computer, that's why the USB interface is optoisolated.
The case is a standars steel box. The same was used in my generator project.
The original author of this oscilloscope and author of this application is MKEiA. Here are some screens showing all this working. The input signal is from MAX038 generator.
1kHz - square
1kHz - sin
1kHz - triangle
100kHz - square
100kHz - sin
100kHz - triangle