Hi, I’m working with a Rapsberry Pi Pico to make a 16 step sequencer, and wondering how to drive 16 LEDs for display feedback.
The classic solution would be daisy chaining two 74hc595 shift registers, and I think I’ll go with that, but is there any other alternative solution?
I also saw Adafruit NeoPixel products which requires 3 or 4 pins to talk with its built in controller, and come in with different sizes, but I’d like a cheaper solution 
I already have leds.
You could opt for a multiplexer solution lighting leds one at a time in a cyclic way. This saves energy and if the multiplexing is fast enough you will not see any flickering.
A 4 to 16 decoder/demultiplexer like the 74HC154 could work.
is that analog? instead of digital, but I think I can use it anyway, sending 0/5v.
however, in my country that chip is more expensive than the neopixel
How many outputs does the pico have? Wouldn’t that be enough? You can always use simple transistors to switch some more current if that is necessary. Maybe it is a good idea to show the schematic you are following here, so we can read along.
Maybe consider a dedicated led driver like the TLC5940. It has the advantage of only needing a single resistor for all leds. But this particular one is no longer in production and hard to get, maybe you find some replacement or similar chip…
I don’t have schematic yet, I would need to draw.
The board has 26 gpio pins. I’m using 3 for the DAC, 3 for a switch rotary encoder, 1 tempo led, 1 analog for the volume pot, and 4 for switches.
That results in 14 free, but I’d like to add 4 switches more, so I’ll have 10 free I guess
Addressable I2C LED Strip.
Leds do not need a separate output each. Ever heard of tuco-plexing or charlie-plexing (have a look at wikipedia)? Similarly not all switch need their own input.
interesting, I’ll read
well, LED strips usually have a single control pin, not sure how they work (pwm?)