Alvaro,
Thanks!
The Peggy is this product, designed by Evil Mad Scientist Laboratories - http://www.evilmadscientist.com/article.php/Peggy2.
The rows are sinked through STP16DP05 LED Drivers. The columns are provided current by STX790A PNP transistors, controlled by 74HC154 multiplexers.
The multiplexers cycle through the 30 columns as fast as the microcontroller can handle it, and the LED driver sinks the appropriate LEDs in that powered column. The refresh rate is not visible, so it's pretty fast.
The display can be modulated with software PWM, as described here - Programming Peggy 2.0 | Evil Mad Scientist Laboratories
Could you describe to me the benefits of using a CPLD/FPGA? Our current setup is pretty straightforward currently, but we're always interested in ideas to improve it.