From Sven Kreiss
Disclaimer: This is an old project of mine. It was done in 2006 and some parts might be out of date. I cannot guaranty proper functionality or fitness for any particular use.
It is an open-source electronic project to build a low-cost digital oscilloscope with an 8-bit microcontroller and a mobile phone display.
- 4 input channels
- no fixed frequencies; the ADC can be run with different clock cycles and then the time for one x-division is displayed in the display; the "td" value (in the images below, 47 microseconds and 9 milliseconds)
- the display also shows a frequency estimate of the signal. The algorithm looks at the time between to successive crossings of the x-axis and calculates a frequency from that. For sine waves, this is reasonably accurate. In the right picture below I measure background noise with a frequency of 49 Hz; the left picture shows a 43 kHz oscillation.
Please be aware that I built only one version. There are many flaws in that one version, but all photos/videos shown here are made with this version.
While playing around with this prototype, I was already making improvements to layout and board which I never built or tested.