Python 3 script to control Arduino PWM

fan_control.py

#!/usr/bin/python3
"""Control an Arduino over the USB port."""

# Based on:
# usb.py
# Created by John Woolsey on 12/17/2019.
# Copyright (c) 2019 Woolsey Workshop.  All rights reserved.

# Reference:
# https://www.woolseyworkshop.com/2020/02/05/controlling-an-arduino-from-a-raspberry-pi/

# Dependencies:
# pip3 install serial
# pip3 install pyserial


# USB_PORT = "/dev/ttyUSB0"  # Arduino Uno R3 Compatible
USB_PORT = '/dev/ttyACM0'  # Arduino Uno WiFi Rev2


# Imports
import serial


# Functions
def print_commands():
   """Prints available commands."""
   print("Available commands:")
   print("  set_fan_1 - Set FAN 1 speed (0-255)")
   print("  set_fan_2 - Set FAN 2 speed (0-255)")
   print("  get_fan_1 - Get FAN 1 speed")
   print("  get_fan_2 - Get FAN 1 speed")
   print("  x - Exit program")


# Main

# Connect to USB serial port at 9600 baud
try:
   usb = serial.Serial(USB_PORT, 9600, dsrdtr=False)
except:
   print("ERROR - Could not open USB serial port.  Please check your port name and permissions.")
   print("Exiting program.")
   exit()
# Send commands to Arduino
print("Enter a command from the keyboard to send to the Arduino.")
print_commands()
while True:
   command = input("Enter command: ")
   if command == "set_fan_1":  # Set speed for FAN 1
      speed = 0
      while True:
         speed = input("Fan speed FAN 1 (0-255): ")
         speed = speed.strip()
         if speed.isdigit():
            break;
      cmd = 'set_fan_1===' + speed
      usb.write(cmd.encode())
      #usb.write(b'set_fan_1===' + speed)
      print("Set speed FAN 1 to :" + speed)
   elif command == "set_fan_2":  # Set speed for FAN 2
      speed = 0
      while True:
         speed = input("Fan speed FAN 2 (0-255): ")
         speed = speed.strip()
         if speed.isdigit():
            break;
      cmd = 'set_fan_2===' + speed
      usb.write(cmd.encode())
      print("Set speed FAN 2 to :" + speed)
   elif command == "get_fan_1":  # turn off Arduino LED
      usb.write(b'get_fan_1')  # send command to Arduino
      line = usb.readline()  # read input from Arduino
      line = line.decode()  # convert type from bytes to string
      line = line.strip()  # strip extra whitespace characters
      if line.isdigit():  # check if line contains only digits
         value = int(line)  # convert type from string to int
      else:
         print("Unknown value for Fan 1: '" + line + "'.")
         value = 0
      print("Fan 1 value:", value)
   elif command == "get_fan_2":  # turn off Arduino LED
      usb.write(b'get_fan_2')  # send command to Arduino
      line = usb.readline()  # read input from Arduino
      line = line.decode()  # convert type from bytes to string
      line = line.strip()  # strip extra whitespace characters
      if line.isdigit():  # check if line contains only digits
         value = int(line)  # convert type from string to int
      else:
         print("Unknown value for Fan 2: '" + line + "'.")
         value = 0
      print("Fan 2 value:", value)
   elif command == "x":  # exit program
      print("Exiting program.")
      exit()
   else:  # unknown command
      print("Unknown command '" + command + "'.")
      print_commands()