There is a very nice tutorial about hooking up the Arduino to the LCD and using the LiquidCrystal library on the Arduino web-site.Ī couple of things that I needed to change:
Still, I would like to have some idea, about how things are working, before hooking up the wires and uploading someone else’s sample code. The process of controlling the display involves putting the data that want to display into the Data registers and writing instructions in the Command register to display the data.Įffects like scrolling text are achieved by a combination of instructions:įortunately, the the LiquidCrystal Library simplifies the communication, so you do not really need to worry about most of that. From the reading I did on the Arduino forums, the 4bit mode is sufficient for displaying characters and since it needs less Arduino pins, most examples use that mode. There are two modes of communication to HD44780 compatible LCDs: 4 bit (using only pins 11 to 14) and 8 bit (using pins 7-14). If you use an Arduino to control the LCD, any digital pin will work. The control lines RS, R/W, and E, along with the data lines (pins 7 to 14) are standard digital logic inputs / outputs. It is initially set to “high” to begin writing the transactions to the registry and then (after a small delay to allow for the LCD to accept the data that is sent) set back to “low” to finish the writing cycle. 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.
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
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.
#Coding lcd arduino drivers
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.
#Coding lcd arduino how to
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. A couple of days ago I came across a discarded Meridian PBX phone and naturally, took it apart.
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