Prerequisites

This project assumes you are familiar with the following projects/lessons:

• Phidgets and the Raspberry Pi
• Make a Website (Raspberry Pi)
• Display Data on Website (Raspberry Pi)
• Display Graph on Website (Raspberry Pi)
• Schedule Tasks with Cron

Setup

Before getting started, make sure you have the following parts.

Logging Soil Data

The first step is to log soil mositure data to a file. To do this, create a Python script called soil.py on your Desktop and copy the code below into the script.

If you need a reminder of how create a Python script with Phidgets, revisit the Getting Started Course.

  
#Add Phidgets library
from Phidget22.Phidget import *
from Phidget22.Devices.VoltageRatioInput import *
#Required for sleep statement
import time
#Used to get current time
from datetime import datetime
#Used to check file status
import os

#Check file status
if(not os.path.isfile('/var/www/html/soil_data.csv')):
    with open('/var/www/html/soil_data.csv','x') as datafile:
        datafile.write("Date,Soil\n")

#Create
soil = VoltageRatioInput()

#Open
soil.openWaitForAttachment(1000)

#Get time
now = datetime.now()

#Format time
time_string = now.strftime("%Y-%m-%dT%H:%M:%SZ")

#Get soil moisture level
soil_string = str(soil.getVoltageRatio())

#Write data to file in CSV format
with open ('/var/www/html/soil_data.csv','a') as datafile:
    datafile.write(time_string + "," + soil_string + "\n")   
  

The Python script above does the following

• Checks if a file called soil_data.csv already exists at /var/www/html. If it does not exist, it creates the file and writes the headers for our CSV file.
• Creates and opens the Soil Moisture Phidget.
• Gets the current time and formats it.
• Gets the current soil moisture value.
• Opens the CSV file at /var/www/html/ and writes a single line including the date and the soil moisture level. This file will later be opened by a webpage and the data will be displayed on a graph.

After creating the Python script and copying the contents above, you can try running the program. If it was successful, you should see a file called soil_data.csv appear at this location: /var/www/html

Schedule With Cron

Next, schedule your Python script to run every minute using the cron command below. If you haven't used cron before, check out this project.

  
* * * * * python3 /home/pi/soil.py
  

Modify Your Website

Next, overwrite your index.html at /var/www/html file with the webpage code below. If you haven't set up a webpage with the Raspberry Pi before, visit the prequisites tab above for more information.

  


    
        
        
        
    
    
    
        

            
Plant Data
            

            

        
        

  

Practice

• Try improving the look of the website.
• Try filtering the data from the file so users can view montly data, yearly data, etc.