I’ve got an Arduino UNO board, and a Hitachi HD44780 type LCD. I wanted to write a python program to communicate with the Arduino board. The board can be connected to the computer via USB, and it appears as a COM port. Therefore we can easily communicate with the Arduino serial interface with python.

My aim is to create a python program that takes the input from the keyboard and display on the LCD. The LCD is connected to the Arduino board as mentioned in the Arduino example:

The following is the code for the Arduino:

// include the library code:
#include <LiquidCrystal.h>

// initialize the library with the numbers of the interface pins
LiquidCrystal lcd(12, 11, 5, 4, 3, 2);

void setup() {
  Serial.begin(9600);
  lcd.begin(16, 2);
  lcd.print("start");
}

void loop() {
  if (Serial.available()) {
    delay(100);  //wait some time for the data to fully be read
    lcd.clear();
    while (Serial.available() > 0) {
      char c = Serial.read();
      lcd.write(c);
    }
  }
}

To access the serial ports you need to set up the pySerial module for python. The Python code:

import serial
import time

s = serial.Serial(11, 9600) #port is 11 (for COM12), and baud rate is 9600
time.sleep(2)    #wait for the Serial to initialize
s.write('Ready...')
while True:
    str = raw_input('Enter text: ')
    str = str.strip()
    if str == 'exit' :
        break
    s.write(str)

I’m on a windows machine, and by default the Arduino is connected to COM12. Note that we need to wait for a little while after initializing the serial connection.

Gist: https://gist.github.com/4460208

Reference: http://playground.arduino.cc/interfacing/python