Hi d82k,
If I'd wire your matrix I'd make it like this (I changed the SEG connections only):
This way I think the multiplex would be better handled by the driver (and the LedControl library, I think).
Lines would be lines and cols=cols... easier to address them individually.
Col Pin _______ Pin Row
DIN 1|o |24 DOUT
1 23 DIG 0 2| |23 SEG D 13 4
5 2 DIG 4 3| M |22 SEG DP 12 8
GND 4| A |21 SEG E 3 5
7 8 DIG 6 5| X |20 SEG C 16 3
3 17 DIG 2 6| 7 |19 V+
4 14 DIG 3 7| 2 |18 ISET
8 11 DIG 7 8| 1 |17 SEG G 9 7
GND 9| 9 |16 SEG B 19 2
6 5 DIG 5 10| |15 SEG F 6 6
2 20 DIG 1 11| RED |14 SEG A 22 1
LOAD 12|_______|13 CLK
I'm also using a 22kOhm resistor... I think the leds will just light up a bit brighter... but I guess the extra current wont harm them, as per the info in the datasheet.
I'm a also a novice so... I'm still figuring it out too but from what I've read the capacitors' function is to smooth the current drops and stabilise it since the MAX7219 seems to be quite sensible.
Other heads up when connecting more than one matrix is to loop through all of then in the setup function:
void setup() {
for(int index=0;index<lc.getDeviceCount();index++) {
lc.shutdown(index,false);
}
lc.setIntensity(0,8);
lc.clearDisplay(0);
}