user58338: I want to merge two projects: a "Don't touch your face" hat for Nano and a 7-segment 4-digit display for Uno. I tested both independently and they work. I added an RGB LED to the first, so I use 6 digital pins: 2 for the ultrasonic sensor, 1 for the buzzer, and 3 the RGB LED.
The Nano project takes 6 digital pins and no analog pins, leaving 4 digital pins and 8 analog pins. The Arduino Uno takes 12 digital pins. So I suppose that it's possible to replace the digital pins of the Uno with analog ones at the right voltage.
Even without the Nano project claiming 6 digital pins, the Nano only has 11 digital pins (D2-D12), not enough for a 7-segment 4-digit display. But I couldn't find a tutorial online on how to do so.
Is it possible to use a 7-segment 4-digit display on Arduino Nano?

user81935: There are chips such as the MAX7219 designed to control 7 segment displays from devices such as an Arduino, there are also some well-established libraries such as LEDCONTROL to drive them. In fact the MAX7219 doesn't have to drive 7 seg displays, you can use it to drive any collection of up to 64 LEDs, I use one for a simple illuminated Christmas tree. You'll need some basic soldering skills to connect the chip to an Arduino but it's very simple.
E.g. see: https://www.maximintegrated.com/en/products/power/display-power-control/MAX7219.html

58338: <p>I want to merge two projects: a <a href="https://www.hackster.io/elegoo-official/don-t-touch-your-face-hat-337f4e" rel="nofollow noreferrer">&quot;Don't touch your face&quot; hat for Nano</a> and a <a href="https://create.arduino.cc/projecthub/aboda243/how-to-use-4-digit-7-segment-without-library-b8e014" rel="nofollow noreferrer">7-segment 4-digit display for Uno</a>. I tested both independently and they work. I added an RGB LED to the first, so I use 6 digital pins: 2 for the ultrasonic sensor, 1 for the buzzer, and 3 the RGB LED.</p>
<p>The Nano project takes 6 digital pins and no analog pins, leaving 4 digital pins and 8 analog pins. The Arduino Uno takes 12 digital pins. So I suppose that it's possible to replace the digital pins of the Uno with analog ones at the right voltage.</p>
<p>Even without the Nano project claiming 6 digital pins, the Nano only has 11 digital pins (D2-D12), not enough for a 7-segment 4-digit display. But I couldn't find a tutorial online on how to do so.</p>
<p>Is it possible to use a 7-segment 4-digit display on Arduino Nano?</p>
 81935: <p>There are chips such as the MAX7219 designed to control 7 segment displays from devices such as an Arduino, there are also some well-established libraries such as LEDCONTROL to drive them. In fact the MAX7219 doesn't have to drive 7 seg displays, you can use it to drive any collection of up to 64 LEDs, I use one for a simple illuminated Christmas tree. You'll need some basic soldering skills to connect the chip to an Arduino but it's very simple.</p>
<p>E.g. see: <a href="https://www.maximintegrated.com/en/products/power/display-power-control/MAX7219.html" rel="nofollow noreferrer">https://www.maximintegrated.com/en/products/power/display-power-control/MAX7219.html</a></p>
