However looping through all the elements is really slowing things down since they all have to pass thu serial connection.
Just extend whatever your serial protocol is to contain commands that allow you to address multiple points on your matrix at once. There's no reason to have more than one serial transmission to update the entire array.
If the values of grid are from 0 to 255 then you can declare it as an arrray of bytes
QuoteIf the values of grid are from 0 to 255 then you can declare it as an arrray of bytesYes! So do I use bitwise math? I'm just learning this - not quite there, yet.Can you give me an example? Like, how do I get the values in and out so I can use them as ints in my logic?