Peter,

Nice device the 7219, I used it too, but I phreaked it to drive mains lamps through ZVC opto-isolated triacs. Very tricky to get the circuit values correct to keep the triacs firing until the next refesh, there was no tolerance !

It will be interesting to drive an LED matrix with it. What do you propose ? Putting all the rows on the digit drivers and the segments to the columns ?

Steve