Sorry, you can’t make vvvv run any faster than, I don’t know 120 frames/sec, so that means only 2 updates per sec of your grid at best.
I am pretty sure the arduino has some code somehwere to convert the values it receives from the serial (a string) to a nicely filled array of 64 int elements.
Do you use firmata? (dunno what the current status is on that)
My idea would be to ask the Arduino people (they are almost as nice as the vvvv community ;) ) how you can convert a Serial.read() string that is 64 integers (0 or 1) to something you can feed your LED array with.
Without a code a can’t pinpoint and solve the problem, but I do understand it.
hmm I have arduino<->vvvv communication reading 137 hardware switches (plus some pots) and sending on/off state to the same amount of LED:s using my own serial protocol.
It was a while since I wrote it but I think I encode one 8xLED row as two characters in a string, and then all rows are appended into one string that is sent in one go with the RS232 node. So half a row, 4-LED:s = 4bits = 16 combinations means that each character in the string can be one of 16 symbols, for that I use the series of 16 chars in the ascii chracter table starting from ‘0’ to ‘?’ since at least 0-9 is easily human readable and having them in series makes the arduino code easier.
Arduino code and vvvv patch for 128 red + 9 green LEDs: (colors are of course not important other than that they’re mentioned in the code)