I have made several radio panels COM and NAV. Each connected using 2x multiplexers (output and input). In total, I have 4 multiplexers connected to the Arduino like this:
Multiplexer A: for input connected to pin 3
Multiplexer B: for output connected to pin 4
Multiplexer C: for input connected to pin 5
Multiplexer D: for output connected to pin 4
all Both multiplexers share the address line consisting of the following: GND, VCC, S0, S1, S2, S3, D, L and Signal. When I change the input connected on multiplexer A, output from multiplexer B is fine. However, when I change input from multiplexer C, the output on multiplexer B and D changes at the same time!
Why would cause such interference?