raspberry pi lcd display gpio quotation

I need to select seven GPIO pins for an LCD I"d like to use; six for 4-bit communication and one for (100-300 Hz) PWM LCD brightness control. I prefer blocks of pins rather than scattered pins. For this low-frequency PWM, do it matter whether I use software vs hardware PWM? There are many tutorials for using LCD character displays with the Pi but the ones I"ve seen just say "use these pins" and don"t say why those pins were selected or what other pins you can use (I know you can"t just use any).

Connecting an LCD display to your Raspberry Pi is sure to take any project up a notch. They’re great for displaying sensor readings, songs or internet radio stations, and stuff from the web like tweets and stock quotes. Whatever you choose to display, LCDs are a simple and inexpensive way to do it.

In this tutorial, I’ll show you two different ways to connect an LCD to the Raspberry Pi with the GPIO pins. The first way I’ll show you is in 8 bit mode, which uses 10 GPIO pins. Then I’ll show you how to connect it in 4 bit mode, and that uses only 6 pins. After we get the LCD hooked up I’ll show you how to program it with C, using Gordon Henderson’s WiringPi LCD library.

I’ll show you how to print text to the display, clear the screen, position the text, and control the cursor. You’ll also see how to scroll text, create custom characters, print data from a sensor, and print the date, time and IP address of your Pi.

There’s another way to connect your LCD that uses only two wires, called I2C. To see how to do that, check out our tutorial How to Set Up an I2C LCD on the Raspberry Pi.

Most people probably want to connect their LCD in 4 bit mode since it uses less wires. But in case you’re interested, I’ll show you how to connect it in 8 bit mode as well.

In 8 bit mode, each command or character is sent to the LCD as a single byte (8 bits) of data. The byte travels in parallel over 8 data wires, with each bit travelling through it’s own wire. 8 bit mode has twice the bandwidth as 4 bit mode, which in theory translates to higher data transfer speed. The main downside to 8 bit mode is that it uses up a lot of GPIO pins.

In 4 bit mode, each byte of data is sent to the LCD in two sets of 4 bits, one after the other, in what are known as the upper bits and lower bits. Although 8 bit mode transfers data about twice as fast as 4 bit mode, it takes a longer time for the LCD driver to process each byte than it takes to transmit the byte. So in reality, there isn’t really a noticeable difference in speed between 4 bit mode and 8 bit mode.

If you’ve never worked with C programs on the Raspberry Pi, you may want to read our article How to Write and Run a C Program on the Raspberry Pi first. It will explain how to write, compile, and run C programs.

WiringPi is a C module that makes it easy to program the LCD. If you already have WiringPi installed on your Pi, you can skip this section. If not, follow the steps below to install it:

WiringPi has it’s own pin numbering system that’s different from the Broadcom (BCM) and RPi physical (BOARD) pin numbering systems. All of the programs below use the WiringPi pin numbers.

To use different pins to connect the LCD, change the pin numbers defined in lines 5 to 14. You’ll need to convert the WiringPi pin numbers to the physical pin numbers of the Raspberry Pi. See here for a diagram you can use to convert between the different numbering systems.

To use the LCD in 4 bit mode, we need to set the bit mode number to 4 in the initialization function (line 20 below). The following code prints “Hello, world!” to the screen in 4 bit mode:

By default, text is printed to the screen at the top row, second column. To change the position, use lcdPosition(lcd, COLUMN, ROW). On a 16×2 LCD, the rows are numbered from 0 to 1, and the columns are numbered from 0 to 15.

The function lcdClear(lcd) clears the screen and sets the cursor position at the top row, first column. This program prints “This is how you” for two seconds, clears the screen, then prints “clear the screen” for another two seconds:

Each LCD character is a 5×8 array of pixels. You can create any pattern you want and display it on the LCD as a custom character. Up to 8 custom characters can be stored in the LCD memory at a time. This website has a nice visual way to generate the bit array used to define custom characters.

To print a single custom character, first define the character. For an example of this see lines 12 to 19 below. Then use the function lcdCharDef(lcd, 2, omega) to store the character in the LCD’s memory. The number 2 in this example is one of the 8 locations in the LCD’s character memory. The 8 locations are numbered 0-7. Then, print the character to the display with lcdPutchar(lcd, 2), where the number 2 is the character stored in memory location 2.

Here’s an example of using multiple custom characters that prints the Greek letters omega, pi, and mu, plus thermometer and water drop symbols for temperature and humidity:

As an example to show you how to display readings from a sensor, this program prints temperature and humidity readings to the LCD using a DHT11 temperature and humidity sensor. To see how to set up the DHT11 on the Raspberry Pi, see our article How to Set Up the DHT11 Humidity Sensor on the Raspberry Pi.

Hopefully this helped you get your LCD up and running on your Raspberry Pi. The programs above are just basic examples, so try combining them to create interesting effects and animations.

If you have any problems or questions about installing the LCD or programming it, just leave a comment below. And don’t forget to subscribe to get an email when we publish new articles. Talk to you next time!

The Internet is full of real time data. Weather information, stock quotes, etc, can be obtained from different service providers. Since most of the Raspberry Pi computers come with Wifi, and it’s extremely easy to handle the data obtained from the Internet with Python, it makes sense to use Raspberry Pi to fetch data from the Internet automatically.

On the other hand, every Raspberry Pi comes with GPIOs, which can be used to connect different devices. For example, we can connect a 16 x 2 character LCD display to the Raspberry Pi.

A communication interface called I2C is frequently used by many devices. Any I2C device uses 4 pins: one for power, one for the ground, one for data (“SDA”) and one for clock signals (“SCL”). For instance, this character LCD display can be connected to Raspberry Pi or other microcontroller via I2C.

This all sounds complicated. Fortunately, Adafruit has created the CircuitPython library for the Raspberry Pi. With this library, we can use I2C devices on Raspberry Pi very easily.

To achieve the above learning outcomes, we will use a Raspberry Pi Zero W to fetch some weather data from the Internet, and display the fetched data on a character LCD screen:

We usually use a browser to look for information on the Internet. We type a URL in the browser, and the browser will display an HTML page. However, if you look at the source of a HTML page, you will see that HTML is actually kind of messy.

For example, the Hong Kong Observatory provides a set of Open Data API so it’s actually really easy to get the latest weather update from the Observatory. To get the latest local weather forcast, all you need to do is to enter this URL in the browser:

NOTE: You may see the term ‘RESTful APIs’ from time to time. Many of these data services are indeed RESTful APIs, which means you can interact with these services with standard HTTP methods (GET, POST, etc.). Since we only need to get this time, we won’t go into the details of RESTful APIs.

Next, we are going to install two Python libraries: Adafruit’s CircuitPython and the library for the LCD1602 display. Let’s create a new folder on the Raspberry Pi for this project inside the terminal.

Then, make sure that the Raspberry Pi Zero W is on the Internet. We will download the libraries from the Internet and install them. If everything is ready, use pip3 to install RPI.GPIO and adafruit-blinka:

NOTE: We only need cd_api.py and circuitpython_i2c_lcd.py only, so it’s better to just copy the python scripts and not to install the entire library.

Both board and busio are from the CircuitPython library. As you will see in a minute, you don’t need to worry about typing the wrong pin numbers when you initialize an I2C device if you use the CircuitPython library. Also, we import the I2cLcd class and the sleep function.

This is where the CircuitPython really shines: the exact same code can be used in other microcontrollers running CircuitPython! So if you get yourself a Circuit Playground Bluefruit, you can use the character LCD display with the exact same code.

DEFAULT_I2C_ADDR = 0x27 defines the address of character LCD display. Every I2C device has an address. This address is important because multiple I2C devices can be connected to the Raspberry Pi, and the Raspberry Pi needs that address to communicate with the device correctly. Finally, we create an instance of I2cLcd with the i2c object, the I2C address, the number of rows and the number of columns as the parameters for the constructor. The backlight is turned on by calling the backlight_on method.

NOTE: This particular LCD1602 display’s address is 0x27, but yours may have a different one. You may need to call busio.I2C.scan() to check the actual address, as described in this Adafruit guide.

Next, rather than printing out all the JSON data in the console, we extract the information that we want and display it on the LCD display. For example, we can just display the temperatures in different regions. Replace print(data) with the following lines of code:

For each entry in the temp_data array, we first clear the display by calling clear(). Then, we move the cursor to (0, 0), i.e. the first position in the first row, and display the first 16 characters of the ‘place’ entry (a string) in the first row. Similarly, we move the cursor to (0, 1), i.e. the first position in the second row, and display the ‘value’ entry (a number). Finally, we pause the program for 2 seconds before showing the next entry.

You can get other data like real time stock quotes in the same way, and create things that are more exciting, such as stock market analysis with AI. Also, you can use other methods in the requests library to interact with other RESTful APIs. For instance, you can POST the data from a sensor attached to a Raspberry Pi to a Google Sheets spreadsheet via Google’s APIs. The possibility of this paradigm is only limited by our imagination.

some jokes (dark jokes preferably, because I"m a horrible human being) displayed from JokeApi. I basically copied the example script and started from there.

This tutorial builds my first LCD display tutorial so I recommend you watch it first. I received a request to combine inputs with an LCD display so I made the following video for the Raspberry Pi that demonstrates polling switches connected to GPIO pins and interrupt callback functions:

Switches are easy to connect to the Raspberry Pi. One terminal of the switch is connected to ground and the other terminal is connected to any GPIO pin. A pull-up resistor is used on the GPIO side to insure the pin defaults to a high state when the switch is off. Activating the switch grounds the GPIO pin to a low state. The Python GPIO.input() method can read the state of the pin and will return true if the pin is high and false if the pin is low.

The Pi GPIO pins have internal pull-up resistors which can be activated when the pin is set up. Therefore,  you don’t have to add any external resistors as in the circuit above. The pins can also be configured with internal pull-down resistors which insures a default low state.

Make sure you launch Idle with super user privileges which is required to access the GPIO. (Update: super-user privileges are no longer required for GPIO access with the latest version of Raspbian.)The Idle IDE no longer comes with the latest version of Raspbian.  It has been replaced by the Thonny Python IDE.

The LCD display wiring differs from my first video as show below. You can use any 6 GPIO pins for RS, Enable and D4-D7. I usually select pins that will facilitate filming and programming. Also the pinouts of LCD displays can vary as well as the power requirements  for the backlight so please chec V without a resistor. Even if your display supports 5 V you might want to add a resistor or variable resistor to control the brightness. The same holds true for the contrast pin. I normally use variable resistors for both.

The wiring is different from my video and Adafruit has made breaking changes to the CharLCD library since the video.  Here is the updated code to declare an lcd:

My first example uses polling to check the state of a switch. The GPIO.setup() method sets GPIO pin 16 to an input and turns on the internal pull-up resistor. The GPIO.input() method in the main program loop reads the state of the pin connected to the switch every second and displays the results on an LCD display. A result of 1 indicates the pin is high and the button is not pressed. A zero indicates the pin is low and the button is pressed.

This is a very easy way to monitor a switch. The disadvantage is that there can be button lag or missed presses depending on the speed of the loop and the other code running. Faster loops produce better results but also use up more CPU resources. A better way to check a switch is with interrupts. This method interrupts the program when the state of GPIO pin changes and fires a callback function. The following code uses the GPIO.add_event_detect() method to add an interrupt on GPIO 16 that fires a method called buttonPressed as soon as the switch is released. This is a rising state because the switch is rising from 0 to 3.3 V. Notice that the main program loop is empty, because everything is handle by the interrupt and the callback.from Adafruit_CharLCD import Adafruit_CharLCD

I use a channel list to set up 17 inputs at once. There is a callback function toggleChanged() for the toggle switch. It needs to fire when the switch changes in both directions so the GPIO.BOTH parameter is passed during setup to catch falling and rising events. The function either displays the results or clears the display. There is another callback function keypadPressed() to handle the keypad button presses. A loop is used to generate the 16 keypad button interrupts.

This is a LCD display HAT for Raspberry Pi, 1.44inch diagonal, 128x128 pixels, with embedded controller, communicating via SPI interface. It also comes with three push button and a joystick, a good option as user interface panel for your Raspberry Pi Zero :)

The screen will not connect to HDMI as it uses SPI to connect and the bandwidth through this will not give anything like real-time video so at best you will get text / polygon drawing.

Wiring for SPI devices is well documented - I would start here on the RPF website SPI0 is common to all models of Pi (it helps if you say what Pi you are planning on using).

I recently received a new Raspberry Piand wanted to create an Intro to Raspberry Pi project. My Pi included a 16x2 LCD display and a Wi-Pi Card so I created the Wireless Raspberry Pi Powered Joke Machine. Just press the push-buttons and the machine will look up a one-liner and scroll through it. (Admission of guilt here...I originally thought it would be neat to create a desk-toy that could display inspiring and educational famous quotes...the Joke Machine cando this, but when I found I could just as easily generate one-liners, I decided that would be more fun :-) )

This Step by Step Instructable walks you through the process of setting up a new Raspberry Pi, adding the the PiFace Control and Display LCD, the WiPi wireless and the provided python script TheQuoteMachine.py which looks up jokes and quotes on a free service called iheartquotes.com. it"ll also describe how to access your Pi without need for a keyboard or Display using VNC remote access.

A Raspberry Pi comes with "Do it Yourself Filling", that is you decide what flavor of Linux you want on it. An easy way to do this is to use a NOOBS SD card to install Linux

NOOBS stands for New Out of the Box Software. You can buy a pre-installed NOOBS SD card (what I used for this project) or download your own from http://www.raspberrypi.org/downloads.

Next I set up VNC so that I could access my Pi from my normal laptop computer. Vnc is a process that allows me to use Graphical applications without connecting any screen up to the Pi itself.  Here"s how to set it up Install vncserver by running this command on the Pi:

connect from your laptop using the ipaddress and port of the vncserver (and the password you created above) To use vnc when you don"t have a Monitor on the Pi, you can either set up the Pi so vncserver starts automatically at boot time, or connect to the pi by using ssh or winscp to log on commandline style to the Pi and start the server.

Python is already installed on the Raspberry Pi, so to run my Quote Machine script you simply need to Download the script from instructables.com (to your Raspberry Pi)

Now you can run /home/pi/bin/TheQuoteMachine.py  It will connect to the free service http://www.iheartquotes.com and display hilarious one-liners. It does this by running a URL that returns the one-liners back in straight text, splitting the text up into 16 character wide segments and then monitoring the PiFace button events that let you scroll up and down through those segments.

Button 4 is the Quit ButtonInstall Your Quote Machine in a Project Box -steps vary depending on the box you use I used a Sharpie to mark where the LCD display should be mounted on the project box

Im having an issue it might be because I don"t have the pi face installed into it yet but the code Chomd +x /home/pi/TheQuoteMachine.py it doesn"t work I tried to run it in the terminal and python0

Nice one , I was also struck with same idea to create something called "words of wisdom" with Pi. But I would rather like to use C for programming Pi. I"m using WiringPi for GPIO control , can you plase tell me is it possible to replicate that with C. Thanks0

This is a really cool idea! I like the prospect of the joke machine. I had an idea for another function. I am thinking about taking your design and making a Fortune Cookie Machine. I found this little metal fortune cookie at a bookstore and I thought it would be cool to make a device like this and attach the metal cookie thing to it and make it generate fortunes. I have not worked with a Raspberry Pi yet, but I think this would be a really cool project to start working with it, when I can spare some cash to get supplies.

thx! I"d like to see what the fortunecookie looks like. The website I get jokes from also has fortunes. You could find a thermal printer and print them out! surplus stores sometimes have them as old credit card machines. use a model a pi to save some money and store the quotes on the sd card to reduce the need for the Wii pi csrd. Good luck!0