so, to clarify. It's my understanding that with SPI, i can use the same 3 serial lines (clock, latch, data) - but address them via "Slave Select" (OE on the 595? )
This would mean that instead of using 6 pins total to drive my matrix, i could reuse the same serial lines, but use slave select to "address" data to either the RGB or the Blanking SR's. Giving a total of 5 pins.
This gets more interesting because i want to add 164/165 to decode my keypad. Also SPI devices - so i'd use 2 more pins (or a 2 to 4 decoder) to be able to now address 4 seperate SPI "busses" - RGB / Blanking / Keypad Out / Keypad in.
On top of that, my last point was that I was just wondering why the matrix version could not have all 4 SRs on one SPI rather then 2 seperate..
is that any clearer?