I recently purchased a "Logic Sniffer", which is a USB hosted 16 channel logic analyzer at a price of $50.

• "Logic Sniffer".
• Support Forums
• General overview.
• A history of my experiences setting it up.
• Client software.
• Firmware.

If you get one of these, as soon as you receive it you will want to update the firmware (even in 2013 it is still shipping with 2011 firmware), and obtain an up to date version of the client software. Then away you go (maybe).