I have a very puzzling question:::
Built two Charlieplex modules. One is 4x12 the second one is 5x20. Each have the same resistors and drive LED's of different ratings. The 5x20 module has rating 2.2v 4x12 has 3.2v rating I have tested each of the modules separately and they work just fine. However, when I plug both into a single Arduino there is a problem. If I try to turn on an LED in the 5x20 matrix the LED turn on no problem. However, if I then try to turn on any LED in the 4x12 matrix the Pin 0 and Pin 1 get set as OUTPUT and Pin 1 as HIGH. I can't then turn this off? It does not make any difference which LED I turn on in the 4x12 matrix.
I have double checked all of the settings and rewired each board twice only to find the same result.
Is there a limitation in the Arduino that will allow only one module of Charleplex LED's to be run at one time?
Arduino is Mega 2560: