Button with Smart Pi One

In this guide, we will demonstrate how to display a message when a button connected to the Smart Pi One is pressed, using the SmartPi-GPIO library and a pull-down resistor connected to the 3.3V pin.

We will cover the following methods: - CLI commands - Python script - C program

Required Materials

• Smart Pi One
• button (with resistor 10kΩ if necessary)
• Connecting wires
• Breadboard (optional for easier connections)

Wiring Diagram

The button is connected to GPIOG11 (Pin 7) as the input pin for detecting the button press. A 10kΩ pull-down resistor is placed between GPIOG11 and Ground (Pin 7). This setup ensures the pin reads LOW when the button is not pressed and HIGH when the button is pressed due to the connection to 3.3.3V (Pin 1).

Pin Number	Pin Name	Function
1	3.3V	Power Supply
7	GPIOG11	Button Input
7	GND	Ground

Displaying a Message via CLI

You can detect button presses using CLI and print a message accordingly.

Steps:

1. Configure the button pin as input:

   sudo gpio 7 mode in pull-down
   

2. Read the button state:

   sudo gpio 7 read
   

3. Example to display a message: Use a loop to continuously check the button status and display a message when pressed:

   while true; do
     if [ $(sudo gpio 7 read) -eq 1 ]; then
       echo "Button Pressed!"
       break
     fi
     sleep 0.1
   done
   

This will print "Button Pressed!" when the button is pressed.

Using Python

Prerequisites: Configuration of smartpi-gpio

To install SmartPi-GPIO on your Smart Pi One, follow these steps:

1. Update system: ```bash sudo apt update sudo apt-get install -y python3-dev python3-pip libjpeg-dev zlib1g-dev libtiff-dev sudo mv /usr/lib/python3.11/EXTERNALLY-MANAGED /usr/lib/python3.11/EXTERNALLY-MANAGED.old

2. Clone the repository: ```bash git clone https://github.com/ADNroboticsfr/smartpi-gpio.git cd smartpi-gpio

3. Install the library: ```bash sudo python3 setup.py sdist bdist_wheel sudo pip3 install dist/smartpi_gpio-1.0.0-py3-none-any.whl

4. Activate GPIO interfaces: bash sudo activate_interfaces.sh

Displaying a Message with Python

With SmartPi-GPIO and Python, you can write a simple script to detect the button press and display a message.

Steps:

1. Create a Python file:

   nano button_message.py
   

2. Write the following code:

from smartpi_gpio.gpio import GPIO
import time

# Initialize GPIO instance
gpio = GPIO()

# GPIO pin number for the button (GPIOA7)
button_pin = 7

# Configure the button pin as input with pull-down resistor
gpio.set_direction(button_pin, "in", "pull-down")

print("Press the button to display a message...")

while True:
    # Read the button state
    button_state = gpio.read(button_pin)

    if button_state == '1':  # If button is pressed
        print("Button Pressed!")
        break

    time.sleep(0.1)

1. Save and exit (CTRL+X, Y, and Enter).

2. Run the Python script:

   python3 button_message.py
   

When the button is pressed, the message "Button Pressed!" will be displayed.

Displaying a Message with a C Program

You can also detect button presses using a C program and the SmartPi-GPIO library.

Steps:

1. Create a C file:

   nano button_message.c
   

2. Write the following code:

#include <stdio.h>
#include <stdlib.h>
#include "smartpi_gpio.h" // Include SmartPi-GPIO header

int main() {
    // Initialize the GPIO library
    if (gpio_init() == -1) {
        printf("Failed to initialize GPIO.\n");
        return -1;
    }

    int button_pin = 7; // GPIOA7 (Pin 12)

    // Set the button pin as input with pull-down resistor
    gpio_set_direction(button_pin, GPIO_INPUT_PULLDOWN);

    printf("Press the button to display a message...\n");

    while (1) {
        // Read the button state
        int button_state = gpio_read(button_pin);

        if (button_state == 1) {
            printf("Button Pressed!\n");
            break;
        }

        // Small delay to prevent busy-waiting
        usleep(100000); // 100 ms
    }

    // Cleanup and close GPIO
    gpio_cleanup();

    return 0;
}

1. Save and exit (CTRL+X, Y, and Enter).

2. Compile the C program:

   gcc -o button_message button_message.c -lsmartpi_gpio
   

3. Run the program:

   sudo ./button_message
   

When the button is pressed, the message "Button Pressed!" will be displayed.