![]() Pin 6, the Clock (Enable) line, tells the display when you are actually ready to perform the instructions. The downside is that I will not be able to read from the LCD this way, but hey you can’t have it all! To save a pin on my Arduino, I connected the R/W pin to ground (essentially keeping it in write mode all the time). The R/W line (pin 5) indicates whether you intend to read from registers (high) or write to the registers (low). When you write with the RS pin set to high, you are accessing the Data Register and writing characters/data to be displayed on screen. When you perform a read or write with RS (pin 4) set to low, you are accessing the Command Register and giving the LCD module commands like “Clear Display”, “Set Cursor Position” etc. These lines indicate what kind of instructions are going to be sent over the data lines (pins 7-14).Ĭharacter LCD modules are accessed through two “registers”, the Command Register, and the Data Register. Pins 4, 5 and 6 are the control lines for the LCD. To my surprise, greater contrast comes with lower voltage and you should never apply a voltage higher than VCC. ![]() Most character LCDs can achieve good display contrast with a voltage between 5V and 0V on pin 3. I connected a 10K Ohm trimpot, to be able to adjust the contrast manually. By changing the voltage or duty cycle of pin 3, the contrast of the display can be adjusted. Pin 2 is VCC and should be connected to +5V power. Pin 1 is GND and should be grounded to the power supply. The first three pins provide power to the LCD module. Digital I/O pin (Not used in 4-bit operation mode).It is set to high to begin writing an instruction and then to low to finish writing. RS=0: Command transaction, RS=1: Data transaction Contrast adjustment (Analog, Voltage range 0-Vcc, Highest contrast at 0).Here is a description of the LCD pin functions: My LCD had only 14 pins, so no backlight to worry about. Most LCDs with a backlight will already include a current limiting resistor in series, but make sure you confirm that before hooking it up. The value of that resistor depends on the the maximum backlight current and the typical backlight voltage drop, which should be listed in the LCD datasheet. You will need to have a current limiting resistor between the 5v rail and pin 15 of the LCD. This type of LCDs will have 14, or 16 pins, with pins 1-14 used to power and communicate with the LCD and pins 15 and 16 powering the optional backlight. After some poking around on the Internets, I confirmed that the drivers at the back of my “new” LCD were indeed compatible with the Hitachi one. The standard 14 pin female header on my LCD was a good sign. The LiquidCryslal Arduino library seemed like the place to start, but its description specifically mentioned that it works with LCDs based on the Hitachi HD44780 driver. The next thing to find out was how to hook this up to my Arduino Uno. On the back of the LCD I could see five KS00065B LCD Driver chips. The pins were helpfully labeled on the front of the panel (from 1 to 14). There was a ribbon cable attached to the LCD with a 14 pin female connector. Among some of the more promising salvaged components was a 40 x 2 character LCD. set up the LCD's number of columns and rows:Īfter initializing the LCD screen, we can display text on it using the lcd.print() function.A couple of days ago I came across a discarded Meridian PBX phone and naturally, took it apart. initialize the library with the numbers of the interface pins The code for initializing the LCD screen is as follows: #include We will define the number of columns and rows of the LCD screen and the pins that we have connected the LCD screen to. Next, we will initialize the LCD screen in the setup function. To do this, go to Sketch > Include Library > LiquidCrystal. The first step is to include the LiquidCrystal library in the Arduino IDE. Now that the wiring is complete, let’s move on to the programming part. B pin of the potentiometer to the GND pin of the Arduino UNO. ![]() ![]() A pin of the potentiometer to the 5V pin of the Arduino UNO.D4-D7 pins of the LCD screen to pins 5-8 of the Arduino UNO.E pin of the LCD screen to pin 11 of the Arduino UNO.RW pin of the LCD screen to the GND pin of the Arduino UNO.RS pin of the LCD screen to pin 12 of the Arduino UNO.V0 pin of the LCD screen to the middle pin of the potentiometer.VDD pin of the LCD screen to the 5V pin of the Arduino UNO.VSS pin of the LCD screen to the GND pin of the Arduino UNO.Connect the LCD screen to the Arduino UNO as follows: ![]() The first step is to wire the components together. Before we dive into the programming aspect of this project, let’s first discuss the components required to make this project: ![]()
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