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152 changes: 90 additions & 62 deletions content/micropython/03.micropython/01.basics/00. digital-io/digital-io.md
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---

featured: micropython-101
title: '2. Micropython Basics - Digital I/O'
description: 'Learn the basics for loops on MicroPython.'
title: 'Digital I/O'
description: 'A guide to digital inputs and outputs using MicroPython.'
author: 'Pedro Lima'
hero_image: "./hero-banner.png"

tags: [MicroPython, Digital I/O]
---

Digital pins are fundamental for interacting with the physical world using your Arduino board. In this chapter, we'll explore how to use digital pins in MicroPython to:
Digital pins are fundamental for interacting with the physical world using your Arduino board. With them, you can:

- Control outputs, such as turning an LED on and off.
- Read inputs, like detecting the state of a button.
Expand All @@ -20,29 +17,77 @@ Digital signals have two distinct values:

Although they can only represent two states, digital signals are highly useful. Being binary in nature, they directly interface with microcontrollers and processors, making them ideal for tasks requiring fast, on/off communication, such as reading sensors or controlling simple outputs. Their simplicity also gives them a natural resilience to electrical noise, as noise only disrupts digital signals when it is strong enough to cross the threshold between HIGH and LOW states. This makes them reliable for clear, consistent communication in various environments.

In this chapter, we'll explore how to use digital pins in MicroPython.

## Requirements

Before we start, let's check the requirements:

### MicroPython Compatible Arduino Boards

MicroPython is officially supported on several Arduino boards. Here’s a list of the compatible boards:

- [Portenta C33](https://store.arduino.cc/products/portenta-c33)
- [Arduino GIGA R1 WiFi](https://store.arduino.cc/products/arduino-giga-r1-wifi)
- [Portenta H7](https://store.arduino.cc/products/portenta-h7)
- [Portenta H7 Lite](https://store.arduino.cc/products/portenta-h7-lite)
- [Portenta H7 Lite Connected](https://store.arduino.cc/products/portenta-h7-lite-connected)
- [Opta](https://store.arduino.cc/products/opta)
- [Opta Wifi](https://store.arduino.cc/products/opta-wifi)
- [Opta RS485](https://store.arduino.cc/products/opta-rs485)
- [Arduino Nano RP2040 Connect](https://store.arduino.cc/products/arduino-nano-rp2040-connect)
- [Nicla Vision](https://store.arduino.cc/products/nicla-vision)
- [Arduino Nano 33 BLE](https://store.arduino.cc/products/arduino-nano-33-ble)
- [Arduino Nano 33 BLE Rev2](https://store.arduino.cc/products/arduino-nano-33-ble-rev2)
- [Arduino Nano 33 BLE Sense](https://store.arduino.cc/products/arduino-nano-33-ble-sense)
- [Arduino Nano 33 BLE Sense Rev2](https://store.arduino.cc/products/arduino-nano-33-ble-sense-rev2)
- [Arduino Nano ESP32](https://store.arduino.cc/products/arduino-nano-esp32)

### Hardware Components

In this guide, we will be using some additional electronic components:
- LEDs (optional if using the onboard LED)
- Current-limiting resistor (e.g. 220Ω) if using an external LED
- Jumper wires
- Pushbutton
- Breadboard

### Software Requirements

- [Arduino Lab for Micropython](https://labs.arduino.cc/en/labs/micropython) - Arduino Lab for MicroPython is an editor where we can create and run MicroPython scripts on our Arduino board.

***Note that the editor is also available online, at [Arduino Cloud - Arduino Labs for MicroPython](https://lab-micropython.arduino.cc/)***

## Board and Editor Setup

1. Open the [Arduino Lab for MicroPython]() application.
2. Plug the Arduino board into the computer using a USB cable.
![Connect board to computer.]()
3. Press the connection button on the top left corner of the window.
![Connect the editor to the board.]()
4. The connected Arduino board should appear, and we can click it:
![Select board.]()

***Need help installing MicroPython on your board? Visit the [MicroPython installation guide]().***

## Digital Outputs

To control digital outputs in MicroPython, we use the `Pin` class from the `machine` module. Setting a pin as an output allows you to control devices like LEDs, relays, or other actuators.

### Code Example: Blinking an LED

Let's create the classic "Blink" example, where we turn an LED on and off at regular intervals.

**Components Needed:**
### Circuit Diagram

- Arduino board compatible with MicroPython
- LED (optional if using the onboard LED)
- Current-limiting resistor (e.g., 220Ω) if using an external LED
- Jumper wires
Connect an LED to the Arduino board, following the circuit diagram below:

- Connect the anode (+) of the LED to a digital output pin.
- Connect the cathode (-) of the LED through a resistor to `GND`.

**Circuit Diagram:**
![LED circuit.]()

- **Onboard LED**: Many Arduino boards have an onboard LED connected to a specific pin.
- **External LED**:
- Connect the anode (+) of the LED to a digital output pin.
- Connect the cathode (-) of the LED through a resistor to `GND`.
***You can also use the built-in LED on your board, if you do not have an external LED.***

**MicroPython Code:**
After completing the circuit diagram, copy the following code into your editor, and run the script.

```python
from machine import Pin
Expand All @@ -61,22 +106,24 @@ while True:
time.sleep(1) # Wait for 1 second
```

**Explanation:**
Let's take a look at what's included in this code example:

- **Import Modules**: We import `Pin` from `machine` and `time` for delays.
- **Initialize LED Pin**: Create a `Pin` object, setting the pin number and direction (`Pin.OUT`).
- **Initialize LED Pin**: with the `Pin` object, we set the pin number and direction (`Pin.OUT`).
- **Main Loop**:
- `led.value(1)`: Sets the pin to HIGH, turning the LED on.
- `time.sleep(1)`: Pauses the program for 1 second.
- `led.value(0)`: Sets the pin to LOW, turning the LED off.
- The loop repeats indefinitely, causing the LED to blink.
- `led.value(1)` - Sets the pin to HIGH, turning the LED on.
- `time.sleep(1)` - Pauses the program for 1 second.
- `led.value(0)` - Sets the pin to LOW, turning the LED off.
- `while True:` - The loop repeats indefinitely, causing the LED to blink.



## Digital Inputs

Reading digital inputs allows your program to respond to external events, like button presses or sensor signals. In MicroPython, we use the `Pin` class to set up pins as inputs, and we can specify pull modes to stabilize the input readings.

In this section, we will explain the different pull modes, and then try them out, by connecting a **pushbutton** to the Arduino.

### Understanding Pull Modes

When a digital input pin is not connected to a definite HIGH or LOW voltage, it is said to be "floating," which can result in unreliable readings due to electrical noise. To prevent this, we use internal pull-up or pull-down resistors, activated by specifying the pull mode in the `Pin` constructor.
Expand All @@ -88,40 +135,16 @@ These internal resistors are built into the microcontroller and can be enabled i

![We can create a image here to explain that]()



### Pull-Up Mode
### Example: Pull-Up Mode

In pull-up mode, the input pin is internally connected to a HIGH voltage level. When the input device (like a button) is activated and connects the pin to GND, the pin reads LOW (`0`).

**Circuit Diagram for Pull-Up Mode:**

- Connect one side of the button to **GND**.
- Connect the other side to a digital input pin.

![Demo]() TODO: Show Schematic

### Pull-Down Mode

In pull-down mode, the input pin is internally connected to GND. When the input device is activated and connects the pin to a HIGH voltage level (e.g., 3.3V), the pin reads HIGH (`1`).

**Circuit Diagram for Pull-Down Mode:**

- Connect one side of the button to **3.3V** (or **5V**, depending on your board's logic level).
- Connect the other side to a digital input pin.

![Demo]() TODO: Show Schematic

![Pull-up mode circuit.]()

### Code Example: Reading a Button with Pull-Up Mode

**Components Needed:**

- Arduino board compatible with MicroPython
- Push-button switch
- Jumper wires

**MicroPython Code:**
After completing the circuit diagram, copy the following code into your editor, and run the script.

```python
from machine import Pin
Expand All @@ -139,7 +162,7 @@ while True:
time.sleep(0.1)
```

**Explanation:**
Let's take a look at what's included in this code example:

- **Initialize Button Pin**:
- We set up the pin as an input with a pull-up mode (`Pin.PULL_UP`), enabling the internal pull-up resistor.
Expand All @@ -151,17 +174,16 @@ while True:
- Reads the button state and prints a message accordingly.
- A short delay helps debounce the button.

### Example: Pull-Down Mode

In pull-down mode, the input pin is internally connected to GND. When the input device is activated and connects the pin to a HIGH voltage level (e.g., 3.3V), the pin reads HIGH (`1`).

### Code Example: Reading a Button with Pull-Down Mode

**Components Needed:**
- Connect one side of the button to **3.3V** (or **5V**, depending on your board's logic level).
- Connect the other side to a digital input pin.

- Arduino board compatible with MicroPython
- Push-button switch
- Jumper wires
![Pull-down mode circuit.]()

**MicroPython Code:**
After completing the circuit diagram, copy the following code into your editor, and run the script.

```python
from machine import Pin
Expand All @@ -179,7 +201,7 @@ while True:
time.sleep(0.1)
```

**Explanation:**
Let's take a look at what's included in this code example:

- **Initialize Button Pin**:
- We set up the pin as an input with a pull-down mode (`Pin.PULL_DOWN`), enabling the internal pull-down resistor.
Expand All @@ -191,3 +213,9 @@ while True:
- Reads the button state and prints a message accordingly.
- A short delay helps debounce the button.

## Summary

In this guide, we have looked at different ways of interacting with digital pins on an Arduino, using MicroPython:
- How to use digital outputs (turning on/off an LED)
- How the different pull modes work (`PULL_DOWN`, `PULL_UP`)
- How to read a button press using either pull modes.
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