This is a oscilloscope-like circuit for the Tinusaur, it is not a real oscilloscope but could be used as a base for one.
It is built on top of the Tinusaur board (Atmel AVR ATiny85) and Nokia 3310/5110 LCD (PCD8544 controller).
There is also simple preamplifier for the electret microphone connected to the ADC of the MCU.
The audio signal source is combination of my DSO Quad (it has built-in signal generator) and a speaker.