Photoresistor with Smart Pi One

In this guide, we will demonstrate how to read values from a photoresistor connected to the Smart Pi One, using the SmartPi-GPIO library.

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

Required Materials

• Smart Pi One
• Photoresistor
• Resistor (typically 10kΩ for voltage divider)
• Connecting wires
• Breadboard (optional for easier connections)

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
   

2. Clone the repository:

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

3. Install the library:

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

4. Activate GPIO interfaces:

   sudo activate_interfaces.sh
   

Wiring Diagram

The photoresistor is connected to 3.3V (Pin 1). The GND connected to Ground (Pin 6). The Photoresistor Input is connected to GPIOG11 (Pin 7), which will be used to read the voltage.

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

Reading Values via CLI

You can read values from the photoresistor using CLI.

Steps:

1. Configure the pin for analog reading (if necessary, depending on your configuration):

   sudo gpio 12 mode in
   

2. Read the value from the photoresistor:

   sudo gpio read 12
   

3. Example to continuously read and display values: Use a loop to read the photoresistor status and print its value:

   while true; do
     value=$(sudo gpio read 12)
     echo "Photoresistor Value: $value"
     sleep 1
   done
   

This will print the current value read from the photoresistor every second.

Using Python

Reading Values with Python

With SmartPi-GPIO and Python, you can write a simple script to read the value from the photoresistor.

Steps:

1. Create a Python file:

   nano photoresistor_read.py
   

2. Write the following code:

from smartpi_gpio.gpio import GPIO
import time

# Initialize GPIO instance
gpio = GPIO()

# GPIO pin number for the photoresistor (GPIOA0)
photoresistor_pin = 12

# Configure the pin as input
gpio.set_direction(photoresistor_pin, "in")

print("Reading values from the photoresistor...")

while True:
    # Read the value from the photoresistor
    value = gpio.read(photoresistor_pin)
    print(f"Photoresistor Value: {value}")
    time.sleep(1)  # Read every second

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

2. Run the Python script:

   python3 photoresistor_read.py
   

This will continuously print the current value read from the photoresistor every second.