SparkFun Inventor's Kit Experiment Guide - v4.1

Contributors: Joel_E_B, bboyho

Circuit 4A: LCD "Hello, World!"

Printing “Hello, world!” is usually the first thing that programming tutorials will have you do in a new language. This guide starts by blinking an LED, but now we’re going to print out real text using a Liquid Crystal Display (LCD).

Parts Needed

Grab the following quantities of each part listed to build this circuit:

New Components

Character Liquid Crystal Display (LCD)

Character LCDs are designed to show a grid of letters, numbers and a few special characters. This makes them great for printing data and showing values. When current is applied to this special kind of crystal, it turns opaque. This is used in a lot of calculators, watches and simple displays. Adding an LCD to your project will make it super portable and allow you to integrate up to 32 characters (16 x 2) of information.

New Concepts

Contrast

Pin 3 on the LCD controls the contrast and brightness of the LCD. Using a simple voltage divider with a potentiometer, the contrast can be adjusted. As you rotate the knob on the potentiometer, you should notice that the screen will get brighter or darker and that the characters become more visible or less visible. The contrast of LCDs is highly dependent on factors such as temperature and the voltage used to power it. Thus, external contrast knobs are needed for displays that cannot automatically account for temperature and voltage changes.

Pixels

If you look closely at the characters on the LCD, you will notice that they are actually made up of lots of little squares. These little squares are called pixels. The size of displays is often represented in pixels. Pixels make up character space, which is the number of pixels in which a character can exist.

Hardware Hookup

The LCD has 16 pins, and it is polarized. The pins are numbered from left to right, 1 through 16. The LCD utilizes an extremely common parallel interface LCD driver chip from Hitachi called the HD44780. Thankfully, the Arduino community has developed a library to handle a great deal of the software-to-hardware interface. Below is a list of each of the pins on the LCD.

Ready to start hooking everything up? Check out the circuit diagram and hookup table below to see how everything is connected.

Circuit Diagram

Note for Advanced Users: If you know how to read datasheets and schematics, you can also refer to the schematic below as an alternative.

Having a hard time seeing the circuit? Click on the image for a closer look.

Hookup Table

Open the Sketch

To open the code, go to: File > Examples > SIK_Guide_Code-master > SIK_Circuit_4A-LCDHelloWorld

You can also copy and paste the following code into the Arduino IDE. Hit upload, and see what happens!

language:cpp
/*
  SparkFun Inventor’s Kit
  Circuit 4A-HelloWorld

  The LCD will display the words "Hello World" and show how many seconds have passed since
  the RedBoard was last reset.

  This sketch was written by SparkFun Electronics, with lots of help from the Arduino community.
  This code is completely free for any use.

  View circuit diagram and instructions at: https://learn.sparkfun.com/tutorials/sparkfun-inventors-kit-experiment-guide---v41
  Download drawings and code at: https://github.com/sparkfun/SIK-Guide-Code
*/

#include <LiquidCrystal.h>          //the liquid crystal library contains commands for printing to the display

LiquidCrystal lcd(13, 12, 11, 10, 9, 8);   // tell the RedBoard what pins are connected to the display

void setup() {

  lcd.begin(16, 2);                 //tell the lcd library that we are using a display that is 16 characters wide and 2 characters high
  lcd.clear();                      //clear the display
}

void loop() {

  lcd.setCursor(0, 0);              //set the cursor to the 0,0 position (top left corner)
  lcd.print("Hello, world!");       //print hello, world! starting at that position

  lcd.setCursor(0, 1);              //move the cursor to the first space of the bottom row
  lcd.print(millis() / 1000);       //print the number of seconds that have passed since the last reset
}

What You Should See

The LCD screen will show “Hello, world!” On the row below, a counter will count every second that passes.

Contrast Adjust

If you are not seeing any characters, are seeing barely visible characters, or see just white rectangles, then you need to adjust the contrast. Twist the potentiometer very slowly until you can clearly read the display. If you reach the end of the potentiometer's rotation, try twisting in the opposite direction.

Program Overview

1. Import the LCD library.
2. Make an LCD object called “lcd” that will be controlled using pins 8, 9, 10, 11, 12 and 13.
3. “Begin” the LCD. This sets the dimensions of the LCD that you are working with (16 x 2). It needs to be called before any other commands from the LCD library are used.
4. Clear the display.
5. Set the cursor to the top left corner lcd.setCursor(0,0);, then print “Hello, world!"
6. Move the cursor to the first space of the lower line lcd.setCursor(0,1);, then print the number of seconds that have passed since the RedBoard was last reset.

Code to Note

Coding Challenges

Troubleshooting