[RandomTask] has posted a nice tutorial on how to use a FTDI serial to usb converter, and a couple analog to digital converters to make a simple software oscilloscope. Using a “Universal Serial to USB converter” and one of many FTDI break out boards, he first reprograms the chip using FTDI’s programming software to put the device into a FIFO (first in first out) mode.
From there a pair of ADC0820 8 bit digital to analog converters are wired up, and input is fed to a couple 555′s for testing. It should be noted that there is no input protection, so things like voltages above 5 volts, or negative voltages are a big no-no with this setup. It still could be very handy while working with micro controllers or other digital circuits.
Data is then sent to the computer and displayed using a VB.net program, which has some basic features like scale and triggering, but also contains a couple bonuses like Calc Freq and Calc V delta calculation.
Many people have these little serial to usb converters, and might be in need of a simple scope. If you’re one of them, then you can cobble this together pretty darn quickly, and cheaply.