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Recently I did a little project with an Arduino board, using an LCD based on that HD44780 chipset. Reliable, fairly standard. The problem in that project was I essentially ran out of digital control lines. By the time I had analog inputs, SPI, I2C, and this LCD going in 4-bit mode (using 6 lines, 7 if not cheating the Read/Write), I was out of pins. That project finished up fine, but I figured I would investigate using a Serially-enabled LCD for the next thing I did.

The problem with serial-enabled LCD’s is that you can get boring HD44780 parallel units for like a dollar from electronics surplus stores, and the serial-enabled ones are like $80. That’s what put me off them in the past, since I see parts and like to buy a couple and have them sitting in reserve for when I want them.

After this last project I ended up buying a couple of the Sparkfun SerLCD modules. Their unit is pretty cheap ($17 for just the backpack, $25 with an LCD). I got the 5-volt version since the arduino is 5V.

With the HD44780 you have to worry a lot about timing and initialization, although there is an arduino library for them which works fine and abstracts a lot of the mess.

The usage of the SerLCD couldn’t really be simpler. If you send it characters, it prints them on the screen. If you send some special single-byte commands it will do functions like turn the display off, move the cursor, set the position, etc. The SerLCD also has backlight PWM control so you can control the brightness of the illumination of the LCD, which is something you can’t do with a raw parallel HD44780 unit. This is all documented in the SerLCD manual [PDF].

Using the SerLCD with an arduino is also really simply. Send characters out the serial port, and you’re done. There’s already an example in the Arduino Playground that shows this. I recently wrote an actual arduino “library” for another chip I was working with, and so I figured I’d try to apply this blundering knowledge to writing a SerLCD library. There probably are a dozen other libraries that do this already, but this one is mine.

Putting together the SerLCD library means that you can address the SerLCD in that nifty Object-Oriented style that other libraries (LiquidCrystal, Serial, SPI, etc) do without having to fuss with too much precursor setup. Should also make the code more portable between your projects too.

I designed the library to use NewSoftSerial, which you can get from Mikal Hart. I think there are rumblings that NewSoftSerial will get rolled into the main Arduino software eventually, but for now you just have to get it manually. I used NewSoftSerial because the Arduino has a dedicated serial interface on digital pins 0/1 which is also shared with the USB-serial interface. So if you wanted to do USB communication at the same time as drive a SerLCD you need to move the SerLCD to other pins which the Serial class doesn’t do. I think the ArduinoMega’s have multiple hardware serial ports, but I wrote this for an Arduino Duemilanove. Mega’s have tons more digital pins anyway to run HD44780’s directly, so who gives a crap.

If you want to use the HardwareSerial port, the library is trivial to change.

In the library I (tried) to implement all the features of SerLCD. I’ve only tested it with the 16×2 display though, so your mileage may vary. I didn’t include anything towards changing the SerLCD bootup splash or resetting the baud rate, since you have to do those when the SerLCD is first powering up and I didn’t want to be bothered. The only issue I encountered with the SerLCD v2.5 firmware seems to be that it would lock up until powered off/on again if you hammered backlight control commands at it too fast. I put a couple of delay() statements in the backlight settings and haven’t have problems.

Using the library is pretty easy. Download the .zip, and unzip it into your Arduino user-contributed-libraries folder (On Windows, this is your My Documents/Arduino/libraries folder, not inside the Arduino IDE directory. I tested this with arduino-0021 on my Duemilanove with an ATMega168 (not the ATMega328, but there’s no reason it shouldn’t work the same), so again – your mileage may vary.

Download the library here. This version is old, the github version is the current one.

You can also download it from github.

The library includes a demo program in the examples directory. Since most of Arduino is LGPL I made this LGPL, but I know most of you people in your plz send me teh codes mindset don’t obey any licenses. If you don’t like LGPL, tough.

A very basic program would be:

#include <NewSoftSerial.h>;
#include <SerLCD.h>;

// NewSoftSerial Object on pin 2
NewSoftSerial NSS(0,2);
// SerLCD object using that NSS
SerLCD theLCD(NSS); 

void setup()
{
  // Remember to start the NewSoftSerial port 
  // before doing things with the SerLCD
  NSS.begin(9600); 
  Serial.begin(9600);
  // This will attempt to initialize the display to 
  // blank with the backlight on 
  theLCD.begin();   
  // Display some massively important informative text
  theLCD.print("Hello, Jerk"); 
}

void loop() 
{
       // nobody cares  
}

WordPress.com’s code tags are still crap

I tried to do this the “right” way and designed SerLCD to inherit from Print::print , that way it picks up all the methods that print() can do – like formatting floats, handling different variable types – without me having to write a stitch of code. Hopefully it also means it’ll keep lockstep with the Print::print automatically that way, so any new features in Print::print are usable by this. I got this idea from this guy’s post where he implements it for an OLED screen. Yes, I know you’re a much better coder than I. Again, it works for me, any your mileage may vary. If you find this useful, enjoy. If you don’t, well then I don’t care.

Here’s a stupid picture (SerLCD’s Rx is connected to arduino digital pin 2):

and here’s a stupid video: