First we need to install the serial library, as this helps to communicate with Arduino via the USB port communication. Type the following command to install the library:

sudo apt-get install python-serial

The following code controls Arduino from Raspberry Pi; you can now either copy the code inside a file called ControlArduinoFromRasp.py, or just get the complete code from the folder for this project.

The following snippet imports the serial library in Python:

import serial 

We define the serial communication:

Arduino_UNO = serial.Serial('/dev/ttyACM0', 9600) 

Print a message to see that the communication is done:

print("Hello From Arduino!") 

While this executes, the user can enter a command:

while True: 
      command = raw_input('Enter the command ') 
      Arduino_UNO.write(command) 

If it's an H it prints the message; in case it is false it displays LED off:

      if command == 'H': 
            print('LED ON') ...