This page describes a very low cost logic analyser using an 18F2525 PIC microprocessor and a PC. The PIC is used as a hardware capture device which monitors the datalines and records all changes. The buffering, triggering, interpretation and display is handled by a PC program running under Windows. The hardware cost will vary between ˆ15 (RS232 version) and ˆ 30 (USB version). The analyser can operate in a “Fast Sampling” mode, in which the data is sampled into an internal 1K buffer on the PIC and in “Normal Sampling” or “Continious Sampling ” mode in which all data changes are offloaded to the PC in real time and arbritary sampling buffer size is available.
PicLA: a very low cost Logic Analyser - [Link]
http://www.electronics-lab.com/blog/?p=2433