Using an Ultrasonic Sensor with Smart Pi One

This page describes how to use an ultrasonic sensor (e.g., HC-SR04) with the Smart Pi One, providing detailed steps, wiring instructions, and code examples in both Python and C.

Required Materials

• Smart Pi One
• Ultrasonic sensor (e.g., HC-SR04)
• Connecting wires
• Breadboard (optional for easier connections)
• 1kΩ and 2kΩ resistors (for voltage divider)

Required Materials

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

Wiring Diagram

Below is a sample wiring diagram for connecting an ultrasonic sensor to the Smart Pi One:

HC-SR04 Pin	Smart Pi One Pin	Description
VCC	5V	Powers the sensor (5V supply)
GND	GND	Ground connection
TRIG	7	Trigger pin connected to GPIO
ECHO	8	Resistors used to step down voltage from 5V to 3.3V to protect the GPIO pin - 1kΩ + 2kΩ (Voltage Divider)

Important Note:

• ECHO pin (GPIO8) requires a voltage divider to step down the 5V output signal from the sensor to 3.3V, which is safe for the GPIO pin on the Smart Pi One.
• Connect a 1kΩ resistor between the ECHO pin and the GPIO pin.
• Connect a 2kΩ resistor between the GPIO pin and GND to complete the voltage divider.

Prerequisites: Configuration of smartpi-gpio

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

1. Update system:

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

1. Clone the repository:

git clone https://github.com/ADNroboticsfr/smartpi-gpio.git
cd smartpi-gpio

1. Install the library:

sudo python3 setup.py sdist bdist_wheel
sudo pip3 install dist/smartpi_gpio-1.0.0-py3-none-any.whl

1. Activate GPIO interfaces:

sudo activate_interfaces.sh

Using Python

Prerequisites: Configuration of smartpi-gpio

1. Open a terminal on your Smart Pi One.
2. Create a new Python file using nano:

nano ultrasonic_sensor.py

1. Copy and paste the following Python code into the file:

import time
from smartpi_gpio.gpio import GPIO

# Initialize GPIO
gpio = GPIO()
TRIG = 7
ECHO = 8

# Set GPIO pins
gpio.setup(TRIG, gpio.OUT)
gpio.setup(ECHO, gpio.IN)

try:
    while True:
        # Send a pulse
        gpio.output(TRIG, gpio.HIGH)
        time.sleep(0.00001)  # 10 microseconds
        gpio.output(TRIG, gpio.LOW)

        # Wait for the echo to start
        while gpio.input(ECHO) == gpio.LOW:
            start_time = time.time()

        # Wait for the echo to stop
        while gpio.input(ECHO) == gpio.HIGH:
            end_time = time.time()

        # Calculate distance
        duration = end_time - start_time
        distance = (duration * 34300) / 2  # Speed of sound is 34300 cm/s

        print(f"Distance: {distance:.2f} cm")
        time.sleep(1)  # Wait 1 second before next measurement
except KeyboardInterrupt:
    pass
finally:
    gpio.cleanup()  # Clean up GPIO

1. Save the file by pressing CTRL + X, then Y, and finally Enter.

Running the Python Script

To run the Python script, use the following command:

sudo python3 ultrasonic_sensor.py