Edmunds,

You can see from the varying directions of responses that most, if not all, the people do not know what you really wanted. For all the effort that people have put into trying to help, I think they deserve a better explanation of what you wanted.

Just saying.

Ken

 

Unless I misunderstand, I think the op is passing a PWM signal through 4 of the optos so I don't think any form of multiplexing will work for those signals.

I took it to mean he didn't want to waste another 8 digital output pins to drive the 8 LEDs.

So the charlieplexing would use up only another 4 pins, or a serial shift register another 2 pins.

 

I should go with another I2C 8 port I/O expander along with 4 that I already have on the project.

Getting an MCU with higher pin count and correct set of hardware modules would let you eliminate all these port extenders.