{"id":48,"date":"2008-10-17T19:33:44","date_gmt":"2008-10-17T19:33:44","guid":{"rendered":"http:\/\/blog.danplanet.com\/wordpress\/?p=48"},"modified":"2008-10-17T19:33:44","modified_gmt":"2008-10-17T19:33:44","slug":"driving-a-4-bit-lcd-with-an-arduino","status":"publish","type":"post","link":"https:\/\/www.danplanet.com\/blog\/2008\/10\/17\/driving-a-4-bit-lcd-with-an-arduino\/","title":{"rendered":"Driving a 4-Bit LCD with an Arduino"},"content":{"rendered":"

I received my Arduino<\/a> Diecimilia today.  Man, what a cool little device.  I ordered it last weekend with the intent of using it to learn about programming microcontrollers, in hopes of making some neat toys.  One of the first things I wanted to be able to do right away was drive an LCD display.  This is very important because I feel that all devices should have LCD displays.  All of them.  Nowadays, I look down on printers without LCD displays (and network cards for that matter) with utter disgust.<\/p>\n

Anyway, I went to SurplusGizmos<\/a> and found myself a nice and cheap 16×2 backlit LCD display.  It uses the KS0066 controller chip, which is supposedly compatible with the legendary Hitachi HD44780 command set.  Because I couldn’t wait for the Arduino to come, I tested it first with a parallel port and lcdproc<\/a>.<\/p>\n

When the Arduino came today, I was ready to try the LCD with it.  Using the integrated LiquidCrystal library, I was able to drive it in 4- and 8-bit mode.  However, in 4-bit mode, the LCD seemed to have trouble keeping up, as long strings would get garbled pretty badly.  It worked fine in 8-bit mode, so I figured this was likely due to the controller switching upper\/lower nibbles too quickly.<\/p>\n

So, in a bit of shameful C++ fu, I created a derivative library that just subclasses the existing one and puts a 2ms delay after each write operation.  This seems to completely clear up the problem, and I can happily have four digitial IO lines back as a result.<\/p>\n

The code is extremely simple, so I’ll just post it here for the taking.  The header is:<\/p>\n

#include “..\/LiquidCrystal\/LiquidCrystal.h”<\/p>\n

class Slow4BitLCD : public LiquidCrystal {
  public:
    Slow4BitLCD(uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t);
    void write(uint8_t);
};<\/div>\n

…and the implementation is:<\/p>\n

#include <inttypes.h>
#include “WProgram.h”<\/p>\n

#include <Slow4BitLCD.h>
#include “..\/LiquidCrystal\/LiquidCrystal.h”<\/p>\n

Slow4BitLCD::Slow4BitLCD(uint8_t rs, uint8_t rw, uint8_t en, uint8_t d0, uint8_t d1, uint8_t d2, uint8_t d3)
  : LiquidCrystal::LiquidCrystal(rs, rw, en, d0, d1, d2, d3)
{}<\/p>\n

void Slow4BitLCD::write(uint8_t value) {
  LiquidCrystal::write(value);
  delayMicroseconds(2000);
}<\/div>\n

Create an Arduino library called “Slow4BitLCD” and put those two files in (with .h and .cpp extensions, respectively) and you should be in business.<\/p>\n

<\/p>\n","protected":false},"excerpt":{"rendered":"

I received my Arduino Diecimilia today.  Man, what a cool little device.  I ordered it last weekend with the intent of using it to learn about programming microcontrollers, in hopes of making some neat toys.  One of the first things … Continue reading →<\/span><\/a><\/p>\n","protected":false},"author":1,"featured_media":0,"comment_status":"closed","ping_status":"open","sticky":false,"template":"","format":"standard","meta":{"footnotes":""},"categories":[11],"tags":[],"class_list":["post-48","post","type-post","status-publish","format-standard","hentry","category-hardware"],"yoast_head":"\nDriving a 4-Bit LCD with an Arduino - Right Angles<\/title>\n<meta name=\"robots\" content=\"index, follow, max-snippet:-1, max-image-preview:large, max-video-preview:-1\" \/>\n<link rel=\"canonical\" href=\"https:\/\/www.danplanet.com\/blog\/2008\/10\/17\/driving-a-4-bit-lcd-with-an-arduino\/\" \/>\n<meta property=\"og:locale\" content=\"en_US\" \/>\n<meta property=\"og:type\" content=\"article\" \/>\n<meta property=\"og:title\" content=\"Driving a 4-Bit LCD with an Arduino - 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