Driving LEDs with two pins?

Question

Arduino

How to connect three LEDs to ARDUINO via two pins and turn on/off each of them independently?

Answer 1

Depends on how strictly to follow the task statement. You can connect some driver via I2C (as Alexander advises).
You can buy a regular 2 to 4 decoder and just blink the LEDs in turn. If you do this very quickly, you will not see that they are blinking (visually, it will not have time to go out).
The first method is better because you can hang many, many devices on one I2C bus (not just your LED controller) and it is simpler in terms of programming. The second one is better because any two GPIOs and a decoder will go cheaper, but you will have to make a more complex program on an arduino.

Answer 2

I2C I/O device type PCF8574

Answer 3

Easily.
Here is the diagram:
https://yadi.sk/i/GzClHuh3zrlSpQ
control is obvious. power supply + 3.3v.
R1 and R2 are chosen so that with ONE
low level at the output, LED3 does not light, but
only burns with TWO zeros.

Answer 4

On 2 pins, you can connect 4 LEDs and control all 4-I
will look like independently.
Search Google for "2 LEDs per output" there are diagrams and code.
Briefly, we hook two LEDs to one output: One is the anode of the other cathode. The second conclusions of the LEDs through resistors, respectively, one to + the other to -.
The output is configured as an input - the LEDs are off.
Output output \u003d 0 - one is on, 1 - the other is on, quickly change the state (0-1-0-1-0 ....) - both are on