lcd display commands quotation
In this tutorial, I’ll explain how to set up an LCD on an Arduino and show you all the different ways you can program it. I’ll show you how to print text, scroll text, make custom characters, blink text, and position text. They’re great for any project that outputs data, and they can make your project a lot more interesting and interactive.
The display I’m using is a 16×2 LCD display that I bought for about $5. You may be wondering why it’s called a 16×2 LCD. The part 16×2 means that the LCD has 2 lines, and can display 16 characters per line. Therefore, a 16×2 LCD screen can display up to 32 characters at once. It is possible to display more than 32 characters with scrolling though.
The code in this article is written for LCD’s that use the standard Hitachi HD44780 driver. If your LCD has 16 pins, then it probably has the Hitachi HD44780 driver. These displays can be wired in either 4 bit mode or 8 bit mode. Wiring the LCD in 4 bit mode is usually preferred since it uses four less wires than 8 bit mode. In practice, there isn’t a noticeable difference in performance between the two modes. In this tutorial, I’ll connect the LCD in 4 bit mode.
Here’s a diagram of the pins on the LCD I’m using. The connections from each pin to the Arduino will be the same, but your pins might be arranged differently on the LCD. Be sure to check the datasheet or look for labels on your particular LCD:
Also, you might need to solder a 16 pin header to your LCD before connecting it to a breadboard. Follow the diagram below to wire the LCD to your Arduino:
There are 19 different functions in the LiquidCrystal library available for us to use. These functions do things like change the position of the text, move text across the screen, or make the display turn on or off. What follows is a short description of each function, and how to use it in a program.
TheLiquidCrystal() function sets the pins the Arduino uses to connect to the LCD. You can use any of the Arduino’s digital pins to control the LCD. Just put the Arduino pin numbers inside the parentheses in this order:
This function sets the dimensions of the LCD. It needs to be placed before any other LiquidCrystal function in the void setup() section of the program. The number of rows and columns are specified as lcd.begin(columns, rows). For a 16×2 LCD, you would use lcd.begin(16, 2), and for a 20×4 LCD you would use lcd.begin(20, 4).
This function clears any text or data already displayed on the LCD. If you use lcd.clear() with lcd.print() and the delay() function in the void loop() section, you can make a simple blinking text program:
Similar, but more useful than lcd.home() is lcd.setCursor(). This function places the cursor (and any printed text) at any position on the screen. It can be used in the void setup() or void loop() section of your program.
The cursor position is defined with lcd.setCursor(column, row). The column and row coordinates start from zero (0-15 and 0-1 respectively). For example, using lcd.setCursor(2, 1) in the void setup() section of the “hello, world!” program above prints “hello, world!” to the lower line and shifts it to the right two spaces:
You can use this function to write different types of data to the LCD, for example the reading from a temperature sensor, or the coordinates from a GPS module. You can also use it to print custom characters that you create yourself (more on this below). Use lcd.write() in the void setup() or void loop() section of your program.
The function lcd.noCursor() turns the cursor off. lcd.cursor() and lcd.noCursor() can be used together in the void loop() section to make a blinking cursor similar to what you see in many text input fields:
Cursors can be placed anywhere on the screen with the lcd.setCursor() function. This code places a blinking cursor directly below the exclamation point in “hello, world!”:
This function creates a block style cursor that blinks on and off at approximately 500 milliseconds per cycle. Use it in the void loop() section. The function lcd.noBlink() disables the blinking block cursor.
This function turns on any text or cursors that have been printed to the LCD screen. The function lcd.noDisplay() turns off any text or cursors printed to the LCD, without clearing it from the LCD’s memory.
This function takes anything printed to the LCD and moves it to the left. It should be used in the void loop() section with a delay command following it. The function will move the text 40 spaces to the left before it loops back to the first character. This code moves the “hello, world!” text to the left, at a rate of one second per character:
Like the lcd.scrollDisplay() functions, the text can be up to 40 characters in length before repeating. At first glance, this function seems less useful than the lcd.scrollDisplay() functions, but it can be very useful for creating animations with custom characters.
lcd.noAutoscroll() turns the lcd.autoscroll() function off. Use this function before or after lcd.autoscroll() in the void loop() section to create sequences of scrolling text or animations.
This function sets the direction that text is printed to the screen. The default mode is from left to right using the command lcd.leftToRight(), but you may find some cases where it’s useful to output text in the reverse direction:
This code prints the “hello, world!” text as “!dlrow ,olleh”. Unless you specify the placement of the cursor with lcd.setCursor(), the text will print from the (0, 1) position and only the first character of the string will be visible.
This command allows you to create your own custom characters. Each character of a 16×2 LCD has a 5 pixel width and an 8 pixel height. Up to 8 different custom characters can be defined in a single program. To design your own characters, you’ll need to make a binary matrix of your custom character from an LCD character generator or map it yourself. This code creates a degree symbol (°):
The Serial Monitor is a convenient way to view data from an Arduino, but what if you want to make your project portable and view sensor values without access to a computer? Liquid crystal displays (LCDs) are excellent for displaying a string of words or sensor data.
This guide will help you in getting your 16×2 character LCD up and running, as well as other character LCDs (such as 16×4, 16×1, 20×4, etc.) that use Hitachi’s LCD controller chip, the HD44780.
As the name suggests, these LCDs are ideal for displaying only characters. A 16×2 character LCD, for example, can display 32 ASCII characters across two rows.
Character LCDs are available in a variety of sizes and colors, including 16×1, 16×4, 20×4, white text on a blue background, black text on a green background, and many more.
One advantage of using any of these displays in your project is that they are “swappable,” meaning that you can easily replace them with another LCD of a different size or color. Your code will need to be tweaked slightly, but the wiring will remain the same!
Before we get into the hookup and example code, let’s check out the pinout. A standard character LCD has 16 pins (except for an RGB LCD, which has 18 pins).
Vo (LCD Contrast) pin controls the contrast of the LCD. Using a simple voltage divider network and a potentiometer, we can make precise contrast adjustments.
RS (Register Select) pin is used to separate the commands (such as setting the cursor to a specific location, clearing the screen, etc.) from the data. The RS pin is set to LOW when sending commands to the LCD and HIGH when sending data.
R/W (Read/Write) pin allows you to read data from or write data to the LCD. Since the LCD is only used as an output device, this pin is typically held low. This forces the LCD into WRITE mode.
E (Enable) pin is used to enable the display. When this pin is set to LOW, the LCD ignores activity on the R/W, RS, and data bus lines; when it is set to HIGH, the LCD processes the incoming data.
D0-D7 (Data Bus) pins carry the 8 bit data we send to the display. To see an uppercase ‘A’ character on the display, for example, we set these pins to 0100 0001 (as per the ASCII table).
The LCD has two separate power connections: one for the LCD (pins 1 and 2) and one for the LCD backlight (pins 15 and 16). Connect LCD pins 1 and 16 to GND and 2 and 15 to 5V.
Depending on the manufacturer, some LCDs include a current-limiting resistor for the backlight. It is located on the back of the LCD, close to pin 15. If your LCD does not contain this resistor or if you are unsure whether it does, you must add one between 5V and pin 15. It should be safe to use a 220 ohm resistor, although a value this high may make the backlight slightly dim. For better results, check the datasheet for the maximum backlight current and choose an appropriate resistor value.
Let’s connect a potentiometer to the display. This is necessary to fine-tune the contrast of the display for best visibility. Connect one side of the 10K potentiometer to 5V and the other to Ground, and connect the middle of the pot (wiper) to LCD pin 3.
That’s all. Now, turn on the Arduino. You will see the backlight light up. As you turn the potentiometer knob, you will see the first row of rectangles appear. If you have made it this far, Congratulations! Your LCD is functioning properly.
We know that data is sent to the LCD via eight data pins. However, HD44780-based LCDs are designed so that we can communicate with them using only four data pins (in 4-bit mode) rather than eight (in 8-bit mode). This helps us save 4 I/O pins!
The sketch begins by including the LiquidCrystal library. This library comes with the Arduino IDE and allows you to control Hitachi HD44780 driver-based LCD displays.
Next, an object of the LiquidCrystal class is created by passing as parameters the pin numbers to which the LCD’s RS, EN, and four data pins are connected.
In the setup, two functions are called. The first function is begin(). It is used to initialize the interface to the LCD screen and to specify the dimensions (columns and rows) of the display. If you’re using a 16×2 character LCD, you should pass 16 and 2; if you’re using a 20×4 LCD, you should pass 20 and 4.
In the loop, the print() function is used to print “Hello world!” to the LCD. Please remember to use quotation marks " " around the text. There is no need for quotation marks when printing numbers or variables.
The function setCursor() is then called to move the cursor to the second row. The cursor position specifies where you want the new text to appear on the LCD. It is assumed that the upper left corner is col=0 and row=0.
There are many useful functions you can use with LiquidCrystal Object. Some of them are listed below:lcd.home() function positions the cursor in the upper-left of the LCD without clearing the display.
lcd.scrollDisplayRight() function scrolls the contents of the display one space to the right. If you want the text to scroll continuously, you have to use this function inside a for loop.
lcd.scrollDisplayLeft() function scrolls the contents of the display one space to the left. Similar to the above function, use this inside a for loop for continuous scrolling.
lcd.display() function turns on the LCD display, after it’s been turned off with noDisplay(). This will restore the text (and cursor) that was on the display.
If you find the default font uninteresting, you can create your own custom characters (glyphs) and symbols. They come in handy when you need to display a character that isn’t in the standard ASCII character set.
The CGROM stores the font that appears on a character LCD. When you instruct a character LCD to display the letter ‘A’, it needs to know which dots to turn on so that we see an ‘A’. This data is stored in the CGROM.
CGRAM is an additional memory for storing user-defined characters. This RAM is limited to 64 bytes. Therefore, for a 5×8 pixel LCD, only 8 user-defined characters can be stored in CGRAM, whereas for a 5×10 pixel LCD, only 4 can be stored.
After including the library and creating the LCD object, custom character arrays are defined. The array consists of 8 bytes, with each byte representing a row in a 5×8 matrix.
This tutorial includes everything you need to know about controlling a character LCD with Arduino. I have included a wiring diagram and many example codes. These displays are great for displaying sensor data or text and they are also fairly cheap.
The first part of this article covers the basics of displaying text and numbers. In the second half, I will go into more detail on how to display custom characters and how you can use the other functions of the LiquidCrystal Arduino library.
As you will see, you need quite a lot of connections to control these displays. I therefore like to use them with an I2C interface module mounted on the back. With this I2C module, you only need two connections to control the LCD. Check out the tutorial below if you want to use an I2C module as well:
These LCDs are available in many different sizes (16×2 1602, 20×4 2004, 16×1 etc.), but they all use the same HD44780 parallel interface LCD controller chip from Hitachi. This means you can easily swap them. You will only need to change the size specifications in your Arduino code.
For more information, you can check out the datasheets below. The 16×2 and 20×4 datasheets include the dimensions of the LCD and in the HD44780 datasheet you can find more information about the Hitachi LCD driver.
Most LCDs have a built-in series resistor for the LED backlight. You should find it on the back of the LCD connected to pin 15 (Anode). If your display doesn’t include a resistor, you will need to add one between 5 V and pin 15. It should be safe to use a 220Ω resistor, but this value might make your display a bit dim. You can check the datasheet for the maximum current rating of the backlight and use this to select an appropriate resistor value.
After you have wired up the LCD, you will need to adjust the contrast of the display. This is done by turning the 10 kΩ potentiometer clockwise or counterclockwise.
Plug in the USB connector of the Arduino to power the LCD. You should see the backlight light up. Now rotate the potentiometer until one (16×2 LCD) or 2 rows (20×4 LCD) of rectangles appear.
In order to control the LCD and display characters, you will need to add a few extra connections. Check the wiring diagram below and the pinout table from the introduction of this article.
We will be using the LCD in 4-bit mode, this means you don’t need to connect anything to D0-D3. The R/W pin is connected to ground, this will pull the pin LOW and set the LCD to WRITE mode.
To control the LCD we will be using the LiquidCrystal library. This library should come pre-installed with the Arduino IDE. You can find it by going to Sketch > Include Library > LiquidCrystal.
The example code below shows you how to display a message on the LCD. Next, I will show you how the code works and how you can use the other functions of the LiquidCrystal library.
After including the library, the next step is to create a new instance of the LiquidCrystal class. The is done with the function LiquidCrystal(rs, enable, d4, d5, d6, d7). As parameters we use the Arduino pins to which we connected the display. Note that we have called the display ‘lcd’. You can give it a different name if you want like ‘menu_display’. You will need to change ‘lcd’ to the new name in the rest of the sketch.
In the loop() the cursor is set to the third column and first row of the LCD with lcd.setCursor(2,0). Note that counting starts at 0, and the first argument specifies the column. If you do not specify the cursor position, the text will be printed at the default home position (0,0) if the display is empty, or behind the last printed character.
Next, the string ‘Hello World!’ is printed with lcd.print("Hello World!"). Note that you need to place quotation marks (” “) around the text. When you want to print numbers or variables, no quotation marks are necessary.
Clears the LCD screen and positions the cursor in the upper-left corner (first row and first column) of the display. You can use this function to display different words in a loop.
This function turns off any text or cursors printed to the LCD. The text/data is not cleared from the LCD memory. This means it will be shown again when the function display() is called.
Scrolls the contents of the display (text and cursor) one space to the left. You can use this function in the loop section of the code in combination with delay(500), to create a scrolling text animation.
This function turns on automatic scrolling of the LCD. This causes each character output to the display to push previous characters over by one space. If the current text direction is left-to-right (the default), the display scrolls to the left; if the current direction is right-to-left, the display scrolls to the right. This has the effect of outputting each new character to the same location on the LCD.
The following example sketch enables automatic scrolling and prints the character 0 to 9 at the position (16,0) of the LCD. Change this to (20,0) for a 20×4 LCD.
With the function createChar() it is possible to create and display custom characters on the LCD. This is especially useful if you want to display a character that is not part of the standard ASCII character set.
Technical info: LCDs that are based on the Hitachi HD44780 LCD controller have two types of memories: CGROM and CGRAM (Character Generator ROM and RAM). CGROM generates all the 5 x 8 dot character patterns from the standard 8-bit character codes. CGRAM can generate user-defined character patterns.
/* Example sketch to create and display custom characters on character LCD with Arduino and LiquidCrystal library. For more info see www.www.makerguides.com */
After including the library and creating the LCD object, the custom character arrays are defined. Each array consists of 8 bytes, 1 byte for each row. In this example 8 custom characters are created.
In this article I have shown you how to use an alphanumeric LCD with Arduino. I hope you found it useful and informative. If you did, please share it with a friend that also likes electronics and making things!
I would love to know what projects you plan on building (or have already built) with these LCDs. If you have any questions, suggestions, or if you think that things are missing in this tutorial, please leave a comment down below.
LCD connected to this controller will adjust itself to the memory map of this DDRAM controller; each location on the LCD will take 1 DDRAM address on the controller. Because we use 2 × 16 type LCD, the first line of the LCD will take the location of the 00H-0FH addresses and the second line will take the 40H-4FH addresses of the controller DDRAM; so neither the addresses of the 10H-27H on the first line or the addresses of the 50H-67H on the second line on DDRAM is used.
To be able to display a character on the first line of the LCD, we must provide written instructions (80h + DDRAM address where our character is to be displayed on the first line) in the Instruction Register-IR and then followed by writing the ASCII code of the character or address of the character stored on the CGROM or CGRAM on the LCD controller data register, as well as to display characters in the second row we must provide written instructions (C0H + DDRAM address where our character to be displayed on the second line) in the Instructions Register-IR and then followed by writing the ASCII code or address of the character on CGROM or CGRAM on the LCD controller data register.
As mentioned above, to display a character (ASCII) you want to show on the LCD, you need to send the ASCII code to the LCD controller data register-DR. For characters from CGROM and CGRAM we only need to send the address of the character where the character is stored; unlike the character of the ASCII code, we must write the ASCII code of the character we want to display on the LCD controller data register to display it. For special characters stored on CGRAM, one must first save the special character at the CGRAM address (prepared 64 addresses, namely addresses 0–63); A special character with a size of 5 × 8 (5 columns × 8 lines) requires eight consecutive addresses to store it, so the total special characters that can be saved or stored on the CGRAM addresses are only eight (8) characters. To be able to save a special character at the first CGRAM address we must send or write 40H instruction to the Instruction Register-IR followed by writing eight consecutive bytes of the data in the Data Register-DR to save the pattern/image of a special character that you want to display on the LCD [9, 10].
We can easily connect this LCD module (LCD + controller) with MCS51, and we do not need any additional electronic equipment as the interface between MCS51 and it; This is because this LCD works with the TTL logic level voltage—Transistor-Transistor Logic.
The voltage source of this display is +5 V connected to Pin 2 (VCC) and GND power supply connected to Pin 1 (VSS) and Pin 16 (GND); Pin 1 (VSS) and Pin 16 (GND) are combined together and connected to the GND of the power supply.
Pins 7–14 (8 Pins) of the display function as a channel to transmit either data or instruction with a channel width of 1 byte (D0-D7) between the display and MCS51. In Figure 6, it can be seen that each Pin connected to the data bus (D0-D7) of MCS51 in this case P0 (80h); P0.0-P0.7 MCS-51 connected to D0-D7 of the LCD.
Pins 4–6 are used to control the performance of the display. Pin 4 (Register Select-RS) is in charge of selecting one of the 2 display registers. If RS is given logic 0 then the selected register is the Instruction Register-IR, otherwise, if RS is given logic 1 then the selected register is the Data Register-DR. The implication of this selection is the meaning of the signal sent down through the data bus (D0-D7), if RS = 0, then the signal sent from the MCS-51 to the LCD is an instruction; usually used to configure the LCD, otherwise if RS = 1 then the data sent from the MCS-51 to the LCD (D0-D7) is the data (object or character) you want to display on the LCD. From Figure 6 Pin 4 (RS) is connected to Pin 16 (P3.6/W¯) of MCS-51 with the address (B6H).
Pin 5 (R/W¯)) of the LCD does not appear in Figure 6 is used for read/write operations. If Pin 5 is given logic 1, the operation is a read operation; reading the data from the LCD. Data will be copied from the LCD data register to MCS-51 via the data bus (D0-D7), namely Pins 7–14 of the LCD. Conversely, if Pin 5 is given a voltage with logical 0 then the operation is a write operation; the signal will be sent from the MCS51 to LCD through the LCD Pins (Pins 7–14); The signal sent can be in the form of data or instructions depending on the logic level input to the Register Select-RS Pin, as described above before if RS = 0 then the signal sent is an instruction, vice versa if the RS = 1 then the signal sent/written is the data you want to display. Usually, Pin 5 of the LCD is connected with the power supply GND, because we will never read data from the LCD data register, but only send instructions for the LCD work configuration or the data you want to display on the LCD.
Pin 6 of the LCD (EN¯) is a Pin used to enable the LCD. The LCD will be enabled with the entry of changes in the signal level from high (1) to low (0) on Pin 6. If Pin 6 gets the voltage of logic level either 1 or 0 then the LCD will be disabled; it will only be enabled when there is a change of the voltage level in Pin 6 from high logic level to low logic level for more than 1000 microseconds (1 millisecond), and we can send either instruction or data to processed during that enable time of Pin 6.
Pin 3 and Pin 15 are used to regulate the brightness of the BPL (Back Plane Light). As mentioned above before the LCD operates on the principle of continuing or inhibiting the light passing through it; instead of producing light by itself. The light source comes from LED behind this LCD called BPL. Light brightness from BPL can be set by using a potentiometer or a trimpot. From Figure 6 Pin 3 (VEE) is used to regulate the brightness of BPL (by changing the current that enters BPL by using a potentiometers/a trimpot). While Pin 15 (BPL) is a Pin used for the sink of BPL LED.
4RSRegister selector on the LCD, if RS = 0 then the selected register is an instruction register (the operation to be performed is a write operation/LCD configuration if Pin 5 (R/W¯) is given a logic 0), if RS = 1 then the selected register is a data register; if (R/W¯) = 0 then the operation performed is a data write operation to the LCD, otherwise if (R/W¯) = 1 then the operation performed is a read operation (data will be sent from the LCD to μC (microcontroller); it is usually used to read the busy bit/Busy Flag- BF of the LCD (bit 7/D7).
5(R/W¯)Sets the operating mode, logic 1 for reading operations and logic 0 for write operations, the information read from the LCD to μC is data, while information written to the LCD from μC can be data to be displayed or instructions used to configure the LCD. Usually, this Pin is connected to the GND of the power supply because we will never read data from the LCD but only write instructions to configure it or write data to the LCD register to be displayed.
6Enable¯The LCD is not active when Enable Pin is either 1 or 0 logic. The LCD will be active if there is a change from logic 1 to logic 0; information can be read or written at the time the change occurs.
For our first project, we’re using both the inbuilt LCD screen and WiFi module to get text data of famous quotes. Since we’re all nerds at DIYODE, we’ve of course chosen to choose famous programming quotes. The center button of the Wio Terminal will be used to load a new quote and display it on the screen.
WiFi is involved here because we’re using a simple Web API to gather data and display it live. Since it’s connecting to WiFi, we could connect it with virtually any other web interface and make it work.
The ‘wasPressed’ variable will be used during the main loop to ensure we only display one new quote when the button is pressed, and not to continue looking for quotes when the button is held. This is typically referred to as state detection, and we’ll talk about this shortly.void setup() {
Text wrapping is the process of bringing text fields down to the next line on the screen if it’s too long – which is often the case with quotes. The LCD library does have this function built-in, but it wasn’t cooperating for us, so we wrote it ourselves!
Essentially, we’re taking ‘chunks’ out of the text with the substring function and writing each to one line of the Wio Terminal’s LCD screen. The ‘len’ variable describes the number of characters on each line. If the function is confusing, just change some values and observe the effects!
The diagram of the pins on the LCD we use is as follows. We have 16 pins on our LCD screen. Depending on the screen we are going to use, the pins can be on the top, bottom, or both sides of the screen. Some very rare screens have 14 pins because there is no backlighting light. Pins 15 and 16 are used to light up the backlight on displays with display lighting. The backlights are separate from the LCD, so we can use the pin of the backlight by plugging it into a digital port. The connections from each pin to the Arduino will be the same, but it can arrange differently you can pins via the LCD. You can look at the LCD’s datasheet for this.
Warning: You may need to solder a 16-pin cap to your LCD before connecting it to the breadboard. Follow the diagram below to connect the LCD to your Arduino:
Allows communication with LiquidCrystal displays (LCDs). I recognized this library as the way an Arduino/Genuino board controls LiquidCrystal displays (i.e. LCDs) based on the Hitachi HD44780 compatible chipset found in most text-based LCDs. The library runs in 4 or 8 bit mode. You can download the latest version from the GitHub repo by clicking here.
Its task specifies the pins that the Arduino uses to connect to the LCD. We can use a random one of the Arduino’s digital pins to control the LCD. We need to put the Arduino pins in parentheses in this order.
Its function adjusts the pins that the Arduino uses to connect to the LCD. You can use any of Arduino’s digital pins to control the LCD. Put the Arduino pins in parentheses in this order: LiquidCrystal(rs, enable, d4, d5, d6, d7); are LCD pins RS, E, D4, D5, D6, D7.
NOTE: Notice that we refer to the screen as ’lcd’. You can give it a different name if you want, such as “screen”. If you change it, you will need to change the LCD to the new name for the rest of the article.
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For example, suppose you want the LCD pin D7 to be connected to 2 from the Arduino pin. Replace D7 with “7”: LiquidCrystal (RS, E, D4, D5, D6, 12);. In this function we must place it in front of the void setup(); section of the program because we define the pins and if we do not place them at the top, we get an error.
This command adjusts the dimensions of the LCD. We should put it in front of any LiquidCrystal function in the void setup(); section of the program. It must specify the number of rows and columns as lcd.begin(columns, rows);. Through these parameters, we indicate how many rows and how many columns our LCD screen has. On 16x2 LDCs, we need to use lcd.begin(16, 2); or you can use lcd.begin(20, 4); on a 20x4 LCD.
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This command can be used in the void setup(); or void loop(); section. Prints a message in the first column and row of the LCD screen. Usage: Printed to the screen with lcd.print ("message");. Note that you must put quotation marks ("") around the text. When you want to print numbers or variables, no quotation marks are required. With lcd.print(); it can print numbers in decimal, binary, hexadecimal, and octet bases. Let’s make an example right away:
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We can use this command in the void setup(); or void loop(); section. Deletes any text or data displayed on the LCD and positions the cursor in the upper-left corner of the screen (first row and first column).
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This command moves the cursor to row 0 and column 0 of the screen, that is, to the upper-left corner of the screen. If we use lcd.home(); after using the lcd.print(); command, it will overwrite it. For example, let’s write “projedefteri” on the screen and then use the command lcd.home(); and then print “12345” on the screen with lcd.print.
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This command is used to set the position of the screen cursor. It is similar to the lcd.home(); command, but more useful than lcd.home();. Because this command places the cursor (and any written text, etc.) anywhere on the screen that we want. We can use it in the void setup(); or void loop(); section of the program.
The cursor position works with the logic lcd.setCursor(column, row);. The column and row coordinates start from zero and are 0-1 and 0-15 respectively (lcd.setCursor(0-1, 0-15)) For example, let’s print the “projedefteri” by using lcd.setCursor(3, 1); in the void setup(); section of the projedefteri program we did above, sliding the cursor to the bottom row and to the right in the third pixel field.
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This command makes the cursor visible. The cursor is a horizontal line that comes below the characters after we print it on the LCD. The lcd.noCurcor() command closes the cursor. lcd.Curcor() and lcd.noCurcor() can be used in the void loop() section to split the blinking cursor, similar to what we see in many text input fields. Let’s make a flashing cursor right away.
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These commands hide and reappear the text on the screen. The clear(); function serves as a memory, cleaning function, while the noDisplay(); and display(); functions allow the text on the screen to be hidden or visible.
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You can use this command to print different types of data to the LCD, for example, you can print temperature and humidity information from DHT11, distance from an HCSR-04 sensor, and proximity information to the screen. We can also use it to print special characters that we create ourselves.
This command allows us to create our own special characters. Each crankcase of a 16x2 LCD has a width of 5 pixels and a height of 8 pixels. We can define 8 different special characters in a single program. For example, let’s write the letter “ç” as a Turkish character on the screen. If you want to make your own special character, click here.
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This command causes the pixel with the cursor to flash and dim approximately once every 500 milliseconds per cycle. It is used in the void loop() field. The lcd.noBlink() command extinguishes the pixel. Let’s make an example right away.
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This command takes everything we print to the LCD and moves it to the left. We should then use it in the void loop () section with a delay command. The command moves the text 40 fields to the left before returning to the first character. This code moves the text “projedefteri” to the left, one second per character. Let’s see it immediately with a sample code.
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lcd.noAutoscroll() turns off the function lcd.autoscroll(). You can use this function before or after the lcd.autoscroll() function in the void loop() section to create floating text or animated sequences.
This command allows us to set the direction in which it printed the text on the screen. The default mode is from left to right using the command lcd.leftToRight(), but you can use this command if you want to write the text in the opposite direction, as in the example below.
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Some Duet 3D mainboards support a dynamically-configured menu system to use on a 12864 display + encoder. As the Duet 3D electronics are capable of being used in many different configurations, with differing requirements, a fixed menu system is not suitable. Therefore the menu structure is defined in files on the Duet mainboard SD card.
Before a 12864 display can be used, the M918 P1 Enn command must be sent to enable it (P1) and set the encoder resolution and direction (Enn, where nn usually needs to be -4, -2, 2 or 4). This command would normally be put in the config.g file. See M918 in the Gcode dictionary for more details. Example:
Folder /menu of the micro SD card installed in the Duet is used to hold menu files. Each file in /menu defines one page on the display. There must be a file called main in /menu, which is the initial file loaded at startup.
The command must be one of the recognised keywords. Most commands cause a display element to be written to the display. Each parameter is similar to a parameter in G- or M-code, i.e. a letter followed by a number or a string, or a colon-separated sequence of numbers. String parameters must always be enclosed in double-quote characters. Parameters may be optional (depending on the command), in which case default values are assumed.
R is the row number for the top of the display element, in pixels counting down from the top of the display, with R0 being the top row. The default is the same row as used for the previous element. The default at the start of the file is 0.
C is the column number for the left hand edge of the display element, in pixels counting from the left, with C0 being the leftmost column. The default is one pixel after the previous element ends. The default at the start of the file is 0.
T is text to be displayed. In firmware 2.02 and later, the letter T can be omitted because an un-prefixed quoted string will be treated as a T parameter.
button[Rnn] [Cnn] [Wnn] [Fnn] T"text" [Vnn] A"action" [L"filename"]Display selectable text using the specified font. If the text is clicked then execute the specified action. Some actions require a filename.
alter[Rnn] [Cnn] [Wnn] [Hn] [Fnn] [Dnn] NvvDisplay the specified value with the specified width to the specified number of decimal places and allow it to be altered
files[Rnn] [Fnn] Nnn I"initial-directory"Display a list of files N files high and allow one of the files to be selected. The list uses the full width of the display. This menu item type is not available when the Duet is used with a Single Board Computer.
The Hitachi HD44780 LCD controller is an alphanumeric dot matrix liquid crystal display (LCD) controller developed by Hitachi in the 1980s. The character set of the controller includes ASCII characters, Japanese Kana characters, and some symbols in two 40 character lines. Using an extension driver, the device can display up to 80 characters.
The Hitachi HD44780 LCD controller is limited to monochrome text displays and is often used in copiers, fax machines, laser printers, industrial test equipment, and networking equipment, such as routers and storage devices.
Compatible LCD screens are manufactured in several standard configurations. Common sizes are one row of eight characters (8×1), and 16×2, 20×2 and 20×4 formats. Larger custom sizes are made with 32, 40 and 80 characters and with 1, 2, 4 or 8 lines. The most commonly manufactured larger configuration is 40×4 characters, which requires two individually addressable HD44780 controllers with expansion chips as a single HD44780 chip can only address up to 80 characters.
Character LCDs may have a backlight, which may be LED, fluorescent, or electroluminescent. The nominal operating voltage for LED backlights is 5V at full brightness, with dimming at lower voltages dependent on the details such as LED color. Non-LED backlights often require higher voltages.
Character LCDs use a 16-contact interface, commonly using pins or card edge connections on 0.1 inch (2.54 mm) centers. Those without backlights may have only 14 pins, omitting the two pins powering the light. This interface was designed to be easily hooked up to the Intel MCS-51 XRAM interface, using only two address pins, which allowed displaying text on LCD using simple MOVX commands, offering cost effective option for adding text display to devices.
Vee (also V0): This is an analog input, typically connected to a potentiometer. The user must be able to control this voltage independent of all other adjustments, in order to optimise visibility of the display that varies i. a. with temperature and, in some cases, height above the sea level. With a wrong adjustment, the display will seem to malfunction.
In 8-bit mode, all transfers happen in one cycle of the enable pin (E) with all 8 bits on the data bus and the RS and R/W pins stable. In 4-bit mode, data are transferred as pairs of 4-bit "nibbles" on the upper data pins, D7–D4, with two enable pulses and the RS and R/W pins stable. The four most significant bits (7–4) must be written first, followed by the four least significant bits (3–0). The high/low sequence must be completed each time or the controller will not properly receive further commands.
Selecting 4-bit or 8-bit mode requires careful selection of commands. There are two primary considerations. First, with D3–D0 unconnected, these lines will always appear high (binary 1111) to the HD44780 since there are internal pull-up MOSFETs.
The execution times listed in this table are based on an oscillator frequency of 270 kHz. The data sheet indicates that for a resistor of 91 kΩ at VCC=5 V the oscillator can vary between 190 kHz and 350 kHz resulting in wait times of 52.6 µs and 28.6 µs instead of 37 µs. If a display with the recommended 91 kΩ resistor is powered from 3.3 volts the oscillator will run much slower. If the busy bit is not used and instructions are timed by the external circuitry, this should be taken into account.
The original HD44780 character generator ROM contains 208 characters in a 5×8 dot matrix, and 32 characters in a 5×10 dot matrix. More recent compatible chips are available with higher resolution, matched to displays with more pixels.
A limited number of custom characters can be programmed into the device in the form of a bitmap using special commands. These characters have to be written to the device each time it is switched on, as they are stored in volatile memory.
The DT022BTFT uses the same connections as the DT022CTFT, with the exception of the backlight (which has connections shown in the Displaytech datasheet).
The provided display driver example code is designed to work with Microchip, however it is generic enough to work with other micro-controllers. The code includes display reset sequence, initialization and example PutPixel() function. Keep the default values for all registers in the ILI9341, unless changed by the example code provided.
Note that the WR pin becomes the D/CX signal in serial mode. CS is used to initiate a data transfer by pulling it low. At the end of the data transfer, pull the CS pin high to complete the transaction. The timing diagram indicates that you can pull the CS pin high in between the command byte and data bytes within a transfer, but it is unlikely needed if the display is the only device on the SPI bus. To keep things simple, we suggest to leave it low during the entire transaction.
PSFTP allows you to run an interactive file transfer session, much like the Windows ftp program. You can list the contents of directories, browse around the file system, issue multiple get and put commands, and eventually log out. By contrast, PSCP is designed to do a single file transfer operation and immediately terminate.
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