Oooohhhh... I've touched a raw nerve here...

If you read my replies you will understand there is more than one way of doing anything - AND that INCLUDES multiple ways of scanning a segment at a time rather than switching all the segments on simultaneously which (and I will repeat it again) is sloppy and amateurish for the reasons I have already stated - namely massive power consumption and the almost certain need for additional circuitry to either latch the display on, or to handle the excessive driving power requirements. They haven't made a PIC yet to handle 710mA worth of LED's - and that's me being conservative and driving them at 10mA and not at 25mA! Why have a 6VA PSU when you can get away with 1.5VA? Why have a 7805 and great lump of metal for a Heatsink when you can get away with a 10 cent 78L05?

My 'personal rule' for scanning/refreshing a display within 30mS is based on good scientific principles formed from the reaction and persistance times of the Rods and Cones in your Retina (Human Physiology and Performance not covered in your University Engineering Course?). If you think you can scan an LED in a slower time and still get away without flicker - go for it - you might end up with a patentable idea and make yourself a great deal of money.

You know there is no 'correct' way of doing anything, but there sure are crazy ways of doing things which may still achieve the same goal. If you and a competitor both chose to make a 10-digit Frequency Counter, and your competitor came up with a design that was 25% cheaper to manufacture, used 50% fewer/smaller parts and tumpeted the fact that his used 80% less engery when working than yours - you'd be pretty upset about it!

It's like the old engineering joke, but based on fact... the Americans spent a million Dollars developing a pen that could write upside-down and in zero gravity. The Russians used a Pencil...

Allow me to laugh at the crazy designs/ideas...