This is a simple PC voltage oscilloscope using only a PIC12F675, a 20MHz oscillator, and a RS232 level shifter. The PIC takes a sample on GP2, immediately sends it to the PC at 115,200 baud using an software asynchronous serial routine, and repeats. It sends a 8-bit value that is read by the Visual Basic software and displayed on the screen (see examples below). The Visual Basic software deduces the time period between submissions and adjusts the display accordingly.
Visual Basic code example: 675OscilloscopeDR1r1.zip