After building up a Xilinx XC9572XL breakout board from Dangerous Prototypes, Karl Hans Janke needed a JTAG interface (a device to access on-chip debug modules and for other purposes). Instead of forking out for the commercial product, Karl instead device his own version using an Arduino - for next to no cost at all. His Arduino sketch allows direct interaction with the JTAG interface from a serial terminal.
Karl continues with more about the concept of debugging and the JTAG specification, as well as hosting the required sketch for download on his website. And for more, we're on twitter and Google+, so follow us for news and product updates as well.