I purchased a USB based logic analyzer from http://www.usbee.com/ called USBee SX for about $150 and then later purchased the professional software for it. It is was one of the neatest gadgets I have used lately.
I have utilized the logic analyzer on several projects recently, involving VGA, USART, SPI, and even DCC signals. The professional suite software allows for the decoding of custom protocols not included in the program. Hence the tinkering with DCC signals.
This picture demonstrates the logic analyzer with DCC signals on Channels 0 and 1.
This picture demonstrates decoding of VGA signals from my Spartan 3 FPGA board. If you look closely at one of the timing parameters at the bottom, it reads close to 59.9 Hz.
These SPI signals were decoded from a recent project I am working involving a Resistive Touch Screen. I have utilized the Analog Devices IC AD7843.
