20 4 lcd display pin diagram factory
The invention of LCD gives new life to electronic industries and replaces lED and gas plasma techniques. It also replaces the CTR (cathode ray) tube that used for visual display. The input power consumed by the liquid crystal display is less then light-emitting diode and plasma display. In today"s post, we will have look at 20 x 4 LCD, its features, working, applications, and practical implementation in different electronic devices. So let"s get started with the Introduction to 20x4 LCD Module.
In a 20x4 LCD module, there are four rows in display and in one row twenty character can be displayed and in one display eighty characters can be shown.
The liquid crystal display interfacing code is easily accessible. We just required eleven input and output pinouts for the interfacing of the LCD screen.
It is the detailed tutorial on the 20x4 LCD module I have mentioned each and everything related to this Liquid crystal display. If you have any question about it ask in comments. Thanks for reading.
Lcd stands for liquid crystal display. Character and graphical lcd’s are most common among hobbyist and diy electronic circuit/project makers. Since their interface serial/parallel pins are defined so its easy to interface them with many microcontrollers. Many products we see in our daily life have lcd’s with them. They are used to show status of the product or provide interface for inputting or selecting some process. Washing machine, microwave,air conditioners and mat cleaners are few examples of products that have character or graphical lcd’s installed in them. In this tutorial i am going to discuss about the character lcd’s. How they work? their pin out and initialization commands etc.
Character lcd’s come in many sizes 8×1, 8×2, 10×2, 16×1, 16×2, 16×4, 20×2, 20×4, 24×2, 30×2, 32×2, 40×2 etc .Many multinational companies like Philips, Hitachi, Panasonic make their own custom type of character lcd’s to be used in their products. All character lcd’s performs the same functions(display characters numbers special characters, ascii characters etc).Their programming is also same and they all have same 14 pins (0-13) or 16 pins (0 to 15).
In an mxn lcd. M denotes number of columns and n represents number of rows. Like if the lcd is denoted by 16×2 it means it has 16 columns and 2 rows. Few examples are given below. 16×2, 8×1 and 8×2 lcd are shown in the picture below. Note the difference in the rows and columns.
On a character lcd a character is generated in a matrix of 5×8 or 5×7. Where 5 represents number of columns and 7/8 represent number of rows. Maximum size of the matrix is 5×8. You can not display character greater then 5×8 dimension matrix. Normally we display a character in 5×7 matrix and left the 8th row for the cursor. If we use the 8th row of the matrix for the character display, then their will be no room for cursor. The picture below shows the 5×8 dot matrix pixels arrangement.
To display character greater than this dimension you have to switch to graphical lcd’s. To learn about graphical lcds here is a good tutorialGraphical Lcd’s Working and Pin out.
The picture above shows the pin out of the character lcd. Almost all the character lcd’s are composed of the same pin out. Lcd’s with total pin count equal to 14 does not have back light control option. They might have back light always on or does not have a back light. 16 total pin count lcd’s have 2 extra A and K pins. A means anode and K cathode, use these pins to control the back light of lcd.
Character Lcd’s have a controller build in to them named HD44780. We actually talk with this controller in order to display character on the lcd screen. HD44780 must be properly handled and initialized before sending any data to it. HD44780 has some registers which are initialized and manipulated for character displaying on the lcd. These registers are selected by the pins of character lcd.
When we send commands to lcd these commands go to Command register and are processed their.Commands with their full description are given in the picture below.When Rs=0 command register is selected.
When we select the register Rs(Command and Data) and set Rw(read – write) and placed the raw value on 8-data lines, now its time to execute the instruction. By instruction i mean the 8-bit data or 8-bit command present on Data lines of lcd. For sending the final data/command present on the data lines we use this enable pin.Usually it remains en=0 and when we want to execute the instruction we make it high en=1 for some mills seconds. After this we again make it ground en=0.
To set lcd display sharpness use this pin. Best way is to use variable resistor such as potentiometer a variable current makes the character contrast sharp. Connect the output of the potentiometer to this pin. Rotate the potentiometer knob forward and backward to adjust the lcd contrast.
NOTE: we can not send an integer, float, long, double type data to lcd because lcd is designed to display a character only. Only the characters that are supported by the HD44780 controller. See the HD44780 data sheet to find out what characters can we display on lcd. The 8 data pins on lcd carries only Ascii 8-bit code of the character to lcd. How ever we can convert our data in character type array and send one by one our data to lcd. Data can be sent using lcd in 8-bit or 4-bit mode. If 4-bit mode is used, two nibbles of data (First high four bits and then low four bits) are sent to complete a full eight-bit transfer. 8-bit mode is best used when speed is required in an application and at least ten I/O pins are available. 4-bit mode requires a minimum of seven bits. In 4-bit mode, only the top 4 data pins (4-7) are used.
Command 0x30 means we are setting 8-bit mode lcd having 1 line and we are initializing it to be 5×7 character display.Now this 5×7 is some thing which every one should know what it stands for. usually the characters are displayed on lcd in 5×8 matrices form. where 5 is total number of columns and is number of rows.Thus the above 0x30 command initializes the lcd to display character in 5 columns and 7 rows the last row we usually leave for our cursor to move or blink etc.
NOTE:You can send commands in hexadecimal or decimal form which one do you like the result is same because the microcontroller translate the command in 8-bit binary value and sends it to the lcd.
Character Lcd’s can be used in 4-bit and 8-bit mode.Before you send commands and data to your lcd. Lcd must first be initialized. This initialization is very important for lcd that are made by Hitachibecause they use HD44780 driver chip sets. Hd44780 Chip set first has to be initialized before using it. If you don’t initialize it properly you will see nothing on your lcd.
In 4-bit mode the high nibble is sent first before the low nibble and the En pin is toggled eachtime four bits is sent to the LCD. To initialize in 4-bit mode:
To learn more about the difference between 4-bit and 8-bit character lcd mode and operation with demo example visit the tutorial link given below. Demo examples are very easy to understand and one can make changes easily in the code. Please also give us your feed back on the post.
A 20x4 LCD display is very basic module and is very commonly used in various devices and circuits. These modules are preferred over seven segments and other multi segment LEDs. The reasons being: LCDs are economical; easily programmable; have no limitation of displaying special & even custom characters (unlike in seven segments), animations and so on.
A 20x4 LCD means it can display 20 characters per line and there are 4 such lines. In this LCD each character is displayed in 5x7 pixel matrix. This LCD has two registers, namely, Command and Data. This is standard HD44780 controller LCD.
Out of boredom I figured out I"ll write a library from scratch to interface the character LCD display which I got from ebay, quite cheap. Less than 7 pounds. However, I have written before a simple code to interface an LCD from scratch for 8051. So I have some experience and understanding how the character LCD works. The difference now will be, I" ll be using 4 bits, instead of 8 bits to communicate and read the busy flag. Essentially improving the previous code. I chose to write it for Arduino this time, because I have Sanguinololu bought for my 3D printer, and at some point I want to write a LCD user interface for it, from scratch. There won"t be anything spectacular about this tutorial, there are already good articles about this stuff for all kinds of devices. Moreover, arduino has bunch of LCD libraries available for download for free. BUT... in this tutorial I"ll describe problems I encountered and try to be as descriptive I can be so you can understand how the character LCD works, making you able to interface it with any micro-controller available, and even driving it by hand.
If you are a careful reader you would notice, that the LCD in the circuit diagram is 16x2 instead 20x4 like in title. That"s because in eagle by default I couldn"t find one with 20x4. However, most of the displays will use HD44780 as LCD controller, so if you understand how to use a 16x2 or 20x4 display or any character display with this chipset, you should be able to cope with any sized character LCDs. Even the pins are the same for these displays.
After we have wired the LCD I"ll do my best to explain more or less how the LCD works. The addresses, initializations etc. I"ll be referring to this datasheet a lot, so keep it open when reading this article. Off-topic: One thing I want to teach beginners is to read datasheets, in my opinion very valuable skill to have. Even though the HD44780 datasheet is not the best ones I"ve read, I"ll try to fill in the gaps.
I will elaborate on the pins as we go on. The main thing is to understand briefly more or less what they are for. Even though when we will be reading the instruction sheet, you"ll see that the datasheet already provides which control pins you have to set HIGH and which LOW. So don"t worry about it so much.
As the names already suggest instruction register will be accessed for configuring and writing instructions to the LCD. DR register on the other hand will be used for writing the data you want for the display to show (not exactly accurate). You can see DR register as a buffer between two RAMs. It"s a temporary register which will eventually write itself automatically in of the available RAMs - CGRAM or DDRAM, depending on what you have written in IR.
DDRAM is used to temporary store the characters the display will show. So by changing the DDRAM, you will write text on your display. DDRAM stores the characters, how they will be drawn, depending on the code (page 10). You have the ability to put like 8 custom characters in CGRAM, but I won"t be elaborating on that. Actually, that would be a good homework. Try to read the datasheet and improve my code to support custom characters. It"s not that hard believe me.
Basically a busy flag is an indicator that the data from DR register is being written to one of the RAMs. You don"t want to change your data until it has finished writing it to the LCD. Otherwise the data will be corrupt and you end up showing Japanese characters (maybe). Basically the pin D7 is the busy flag, while it logic HIGH it means the data is being written to the LCD, when it"s 0 obviouslly it"s not busy anymore.
Address counter is basically a register, which specifies which block of RAM you want to either read or write to the LCD. It applies to both of the RAMs - DDRAM and CGRAM. While configuring the device, we will be able to set AC to be incremented or decremented automatically, so for most cases you won"t need to worry about it. Until we get to assigning coordinates where the text should be written.
But there is one important thing which I want to elaborate on, I even got confused on this matter. Basically the datasheet will tell you that there it has two modes 1-line display and 2-line display. From our perspective I have 4 line display, so how come there isn"t 4-line display available for DDRAM?
So how did I come up with those numbers. We know that HD44780 can hold up to 80 characters in DDRAM, also we know that 1st line and 2nd line acts as a single 40 character line. It means that when we write 20th character on line 1 it will be 3rd line on the real device. Then just by adding 20, we can get each of the starting addresses.
So far we have covered the main structure of the HD44780 LCD driver. You should now have an intuition of how the data is passed around and how it is stored. For CGRAM, you"ll have figure that on your own. Believe me it"s not that hard.
First thing we want to do is to initialize the display. Please see the Figure 24 on page 46 in datasheet. It has a nice diagram for the initialization.
Note: As you can see in the diagram above, after we have initialized 4 bit mode, the following data will be sent in two blocks. 1. we send the upper bits and the lower one. I will elaborate how to do it later on, but for now think of them as a single byte. For example, function set will be 0010 NF00.
It" s basically instruction to enable/disable the display, to show/hide the cursor and to make the cursor blink. Please refer to page 28 in datasheet.
As you can see it has 3 bits called D, C and B. Those are for configuring the things I mentioned before. But for initializition, we just turn off the display.
Final step you have to take to initialize the display. Basically in entry mode you configure whether the address counter (AC) will increment or decrement automatically and whether the display will shift instead of the cursor.
At this point we kind of have initialized the display, however we have to turn on the display. So after this, we have to call another Display on/off controlinstruction, this time we want to switch it on. And if you want for debugging or any other reason, you can enable now the cursor and the blinking of the cursor as well.
So the first function sendCommand,is for sending 8 bits in parallel. I couldn"t figure out how to merge with 4 bit function, because it is slightly different.
Anyway, remember at the beginning I was describing how the data is sent to the HD44780. Just enable the pins D7-D4 pins accordingly, either wait for busy flag or for couple ms. Taking into account what I now said, we can construct a simple code for sending a byte
Now we have to construct a function which will allow us to send a byte in two blocks. Important is to remember what is shown in figure 9 on page 22. is to trigger the enable pin E, when we have data ready to be sent. It has to be twice, since we are sending the upper bits and the lower bits.
Remember, I was writing that you have to wait until the data is written in the RAM, either you substitute the lcdBusy() function for something like delay(1) or let"s write a function for checking the busy flag. See page 24 in datasheet, what command we have to send to read the busy flag, and which bit we will have to read.
So from the datasheet, we can see that we have to set RS to 0 and R/W to 1, and the BF is located on pin DB7. Taking all that into account, we can now write a function to wait until LCD has finished writing data to RAM. Another thing, because we are using 4 bits, we have to trigger the enable pin to read the upper 4 bits and then lower 4 bits. since we are only interested in BF for now, we can make a dummy trigger.
Basically those are all the necessary functions to communicate with the LCD. Now just to simplify our life, we can write a function to send string of characters automatically. I like to send a pointer to the string of characters and then just increment it until we reach the end. Just see my code you"ll understand.
Now you should be able to send text in a very user friendly manner. It probably would be a good idea to implement a way to move the cursor around the screen. See page 24 in datasheet, on how to set CGRAM address.
Okay, now we have the ability to move the cursor by specifying it"s address. However, it is not very user friendly, it would be easier for a programmer to be able to write XY coordinates rather than CGRAM address. So let"s make a coordinate mapping function.
And that"s it! You have implemented all the basic functions to use a 20x4 HD44780 based character LCD display. I wrote a simple class like library for the arduino.
The Displaytech 204G series is a lineup of 20x4 character LCD modules. These modules have a 98x60 mm outer dimension with 77x25.2 mm viewing area on the display. The 204G 20x4 LCD displays are available in STN or FSTN LCD modes with or without an LED backlight. The backlight color options include yellow green, white, blue, pure green, or amber color. Get a free quote direct from Displaytech for a 20x4 character LCD display from the 204G series.
ERM2004FS-3 is small size 20 characters wide,4 rows character lcd module,SPLC780C controller (Industry-standard HD44780 compatible controller),6800 4/8-bit parallel interface,single led backlight with white color included can be dimmed easily with a resistor or PWM,fstn-lcd positive,black text on the white color,high contrast,wide operating temperature range,wide view angle,rohs compliant,built in character set supports English/Japanese text, see the SPLC780C datasheet for the full character set, It"s optional for pin header connection,5V or 3.3V power supply and I2C adapter board for arduino.
Newhaven 20x4 character Liquid Crystal Display shows characters with dark pixels on a bright yellow/green background when powered on. This transflective LCD Display is visible with ambient light or a backlight while offering a wide operating temperature range from -20 to 70 degrees Celsius. This NHD-0420AZ-FL-YBW-33V3 display has an optimal view of 6:00. This display operates at 3.3V supply voltage and is RoHS compliant.
Adjust the length, position, and pinout of your cables or add additional connectors. Get a cable solution that’s precisely designed to make your connections streamlined and secure.
Easily modify any connectors on your display to meet your application’s requirements. Our engineers are able to perform soldering for pin headers, boxed headers, right angle headers, and any other connectors your display may require.
Choose from a wide selection of interface options or talk to our experts to select the best one for your project. We can incorporate HDMI, USB, SPI, VGA and more into your display to achieve your design goals.
Choose from a wide selection of changes including shape, size, pinout, and component layout of your PCB to make it a perfect fit for your application.
Including
In this situation, if it isn"t already working, looking at or attempting to use the bundled LiquidCrystal_I2c i/o class example is useless since it uses a default constructor with no pin mappings. When no pin mappings are specified, the library will default to the pin mappings for fm"s LCD xio "backpack" which nobody will have and is a different pin mapping from any of the backpacks that are sold on places like amazon, e-bay, bangGood, etc....
For those that don"t know how to fill in the constructor for the newLiquidCrystal LiquidCrystal_I2C object, my suggestion is to use the hd44780 library instead as it is easier to use since it can figure out i2c address and pin mappings so all the examples should "just work" out of the box and sketch code can use a simple / generic constructor to use the self configuration capabilities of the hd44780_I2Cexp i/o class.
Ms.Josey 
Ms.Josey