Repurposing 7 Binary to 7-segment Decoders as an 8:1 MUX.
This circuit describes how I got a decoder to act as a 2:1 MUX https://everycircuit.com/circuit/4846082110259200
If you string these together, you can increase the number of input channels. This one has 8, and each one can be selected with a 3-bit binary number.
So we can serialize 1 byte of parallel data.
One last interesting thing is going on here. The output needs to be inverted. I could have done this using a NOT gate or using a PNP transistor (like my other multiplexer/demultiplexer circuits). But here I use a trick. If you flip the direction of the LED and have the logic output act as a sink instead of a source, you basically have inverted behavior. A logic 1 will block current through the LED, causing it to be OFF (0). A logic 0 will allow current through the LED, causing it to be ON (1).
Left logic sources: Data In
Top logic sources: Selection
RGB LED: Output
1:8 DEMUX https://everycircuit.com/circuit/5973669939249152
4:1 MUX https://everycircuit.com/circuit/4716273367515136
16:1 MUX https://everycircuit.com/circuit/6080373636988928
