Using limited I/Os effectively

Projects General Guidance
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Hi my name is Cody, have had an Arduino Uno for a couple years, but still an amateur building on my skills every other month or so.

Ik most the basics and am trying to make a more interactive program besides just blinking lights, etc. I have a handful of sensors, particularly a joystick. I got it all setup and can view the X/Y on the monitors and even have IF statements to tell me what quadrant the joystick is in like a TIC TAC TOE board I.e. (upper l, upper middle, upper right, etc.).

My project idea is to use 9 LEDS and have them turn on/off as I move the joystick around just as a practice programming joystick movement. I haven’t wired the LEDs yet, but initial thought was to hard wire each LED to a PIN and IF the joystick is in that quadrant to turn the LED to HIGH… overall not to complicated, except for the fact that I don’t think I have enough pins w/ the joystick or if I do none will be left for any other functionality I.e. another sensor, LCD, etc.

Is there a smarter way to tell an individual pin to turn on/off without using 1 pin per LED?

I was thinking of trying to give each row & column a number 1-3 (total of 6 pins: 3x + 3y) and say it’s in the upper right square send a signal through all 3 right hand squares, but only send the signal through the top row of squares i.e. where the 2 signals intersect would be the only square getting full power (don’t mean changing the power output per say, though maybe that is an option… just mean if that square gets 2 YES indicators to turn on)

So if you made it a 4x4 grid instead of needing 16 pins you’d only need 8?

Ik this is a very roundabout question for a very simple project, but feel I have seen people get more functionality out of an UNO than just a joystick and 9 LEDs, but unsure how I could wire it without the number of pins I’m using going through the roof or needing multiple boards.

Any advice or suggestions appreciated!

Edit: searching on YT I have seen things for “chasers” and Cubes, but think the difference between these and what I want to do is individual control… I.e. a chaser, all the LEDs are getting the same input, but delayed… think I similar thing is done with the cubes so even though it’s an 8x8x8… not every LED is getting it’s own signal… still investigating

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You could Google "charlieplexing"

1 Like
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There are also LED matrix that use a MAX7219 to drive them. They only use 3 or 4 pins to control 64 (or way more) LEDs.

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Yes I think this is what I need to learn! Thank you

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Okay I see what you are saying, will probably grab one of those for that is the functionality I am looking for, but was trying to wire it in a more basic setup… I mean basically trying to make that myself using a breadboard, LEDs and resistors… reinventing the wheel but as a learning exercise

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Aliexpress links; Single:

Quad:

Green is nicest. :grin:

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It is never too early to discover and start working with smart LEDs.

Neopixels are one kind. Google it. You can have a large number of LEDs and run them from one pin… no additional hardware except a capacitor and a resistor.

Also I mention the wokwi.com simulator, where you can wire up all kindsa stuff without waiting for the delivery man to bring new supplies and without burning your fingers.

a7

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Another method to utilize more outputs with less pins is using a SIPO shift register such as the SN74HC595. There are some good tutorials on Youtube for it, but you can drive 8 outputs using 3 pins. I used it to drive my 8 channel relay board with 3 pins, and it is very reliable so far.

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3X3 == 9 LEDS, but 3X3 matrix needs only 6 outputs:
3 Outputs for x-cord
3 Outputs for y-cord

image

DO NOT FORGET THE CURRENT LIMITING RESISTORS (3)

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