Automating Photo Capture with Crontab on a Raspberry Pi

1. Project Overview

• Description: This project automates photo capture on a Raspberry Pi, setting up a task to take photos twice a day and upload them to Google Drive. It utilizes crontab for scheduling, Python for capturing and processing the image, and Google Apps Script for storing photos in the cloud.

• Objective: Demonstrate how to use crontab on embedded systems to automate repetitive tasks and improve data accessibility.

• Applications: Monitoring, surveillance, IoT projects, environmental data logging, etc.

2. What is Crontab?

• Overview: crontab is a scheduling tool in Unix/Linux systems that enables automated execution of commands or scripts at specific intervals, making task automation easy and reliable.

• How It Works: crontab uses a configuration file where each line represents a scheduled task. The tasks run according to a specified syntax.

• Basic Syntax:

minute hour day_of_month month day_of_week command

• Examples:

• 0 3 * * * /home/pi/backup.sh: Runs a backup script every day at 3:00 AM.
• */15 * * * * /home/pi/check_status.sh: Runs a script every 15 minutes. 

3. Materials and Tools

• Hardware:

• Raspberry Pi (with a compatible camera).

• Camera

• Software:

• Python: Script to capture and upload photos.

• Google Apps Script: Configured to receive and store photos in a Google Drive folder.

• crontab: Used to automate the Python script execution.

4. Project Steps

• Step 1: Set Up the Camera on Raspberry Pi

• Connect and enable the camera.

• Run an initial test to ensure the camera works correctly.

• Step 2: Create the Python Script for Capture and Upload

• Code to capture a photo, convert it to Base64, and send it to Google Drive using Google Apps Script.

• Example code snippet:

import requests
import base64
import json

def upload_photo_to_gdrive(photo_path):
    url = "https://script.google.com/###"  # Replace it with the URL of your script of Google Apps
    
    # Read the file and convert it to Base64
    with open(photo_path, "rb") as file:
        encoded_file = base64.b64encode(file.read()).decode("utf-8")

    # JSON format Data
    data = {
        'file': encoded_file,
        'filename': 'photo.jpg',
        'mimetype': 'image/jpeg'
    }
    
    # JSON format Data
    headers = {'Content-Type': 'application/json'}
    response = requests.post(url, data=json.dumps(data), headers=headers)
    print(response.text)  # Imprimir la respuesta de Google Apps Script

if __name__ == "__main__":
    photo_path = "photo.jpg"  # User the desired name
    upload_photo_to_gdrive(photo_path)

• Step 3: Set Up Google Apps Script

• Create a new Google Apps Script in Drive to receive images.

• Configure the script to handle image uploads and save them to a specific folder.

function doPost(e) {
try {
// Check the folder by id
var folder = DriveApp.getFolderById("USE THE FOLDER ID");
// Decode on Base64
var data = JSON.parse(e.postData.contents);
var fileData = Utilities.base64Decode(data.file);
var blob = Utilities.newBlob(fileData, data.mimetype, data.filename);
// Create the folder on Google Drive
var file = folder.createFile(blob);
return ContentService.createTextOutput("File uploaded: " + file.getName());
} catch (error) {
return ContentService.createTextOutput("Error App Script: " + error.message);
}
}

• Step 4: Set Up Crontab to Run the Script Automatically

• Add the following command to crontab to execute the Python script at 5:30 AM and 5:30 PM daily:

30 5,17 * * * /usr/bin/python3 /home/pi/upload_photo.py >> /home/pi/photo_log.log 2>&1

• Explanation:

• 30 5, 17: Runs the script at 5:30 AM and 5:30 PM.

• Log Redirection: Directs output and errors to photo_log.log for troubleshooting.

5. Testing and Results

• Verifying Crontab Execution:

• Check the photo_log.log file to confirm that the task runs correctly.

• Verify that images appear in the specified Google Drive folder.

• Common Errors and Solutions:

• Permission issues: Ensure the script has the necessary permissions.

• Network errors: Make sure the Raspberry Pi is connected to the internet.

6. Conclusions

• Automation and Consistency: crontab allows consistent photo capture and upload without manual intervention.

• Scalability: This setup can be adapted to capture other sensor data, monitor environments, and more.

• Flexibility of Crontab: Highlights how crontab can schedule tasks at various intervals, supporting multiple automation applications.

7. Next Steps and Project Expansion

• Power Optimization: Set up the Raspberry Pi to turn off the camera and reduce CPU frequency during inactive hours.

• Notifications: Configure notifications to alert when new photos are captured and uploaded.

• Additional Applications: Add image processing or object recognition to the captured photos.