This is where i run into a problem. The led matrix works by having 8 grounds (one for each row) and 16 inputs (8 green and 8 red). So my question is: Is there a configuration so that the "ground" pins arent the pins going into the TLC5940? I was hoping to use the TLC5940 to control the 16 input pins and have the 8 ground routed directly to the arduino Otherwise i simply wont have enough pins.
The TLC5940 is designed as a 'current sink' which means a connection is either switched off, or looks like it is connected to ground (it sinks current and doesn't source current)
There are some current source/high side chips from TI, or you could use ordinary shift registers to drive the anodes. That'd only need 2 to 4 pins (depending on the type), and if you are careful, you could share the clock and enable for both red and green 'channels'.
A nicer display would have been common anode, where 16 cathode connections would be available for connection to the TLC5940.
HTH
GB
BTW, one TLC5940 could sink current from two of those displays.
As was said you can't drive a matrix from two TLC5940s. However you can multiplex one of them to drive a matrix, like I did here:- http://www.thebox.myzen.co.uk/Hardware/Mini_Monome.html
But if it is just a single colour matrix it is a bit of a waste using this chip.