How to use an LCD character display with a BeagleBone Black?

How to use an LCD character display with a BeagleBone Black?

In the world of embedded systems, the BeagleBone Black stands out as a powerful and versatile single - board computer. When paired with an LCD character display, it can be used for a wide range of applications, from simple status indicators to complex data monitoring systems. As a supplier of LCD character displays, I'm excited to share with you how to integrate an LCD character display with a BeagleBone Black.

Understanding the BeagleBone Black and LCD Character Displays

The BeagleBone Black is equipped with a 1GHz ARM Cortex - A8 processor, 512MB of RAM, and multiple input/output pins. These pins allow it to communicate with various external devices, including LCD character displays.

LCD character displays are widely used for displaying text and simple graphics. They come in different sizes and configurations, such as the 20x2 LCD Display LCD Module, the 0802 LCD Display, and the LCD Display 16x1. These displays typically use the Hitachi HD44780 controller or a compatible one, which has a well - defined communication protocol.

Hardware Connection

Before we start programming, we need to connect the LCD character display to the BeagleBone Black. Here are the general steps:

1. Power Supply: Connect the VSS (GND) pin of the LCD to the ground pin on the BeagleBone Black. Connect the VDD (5V) pin of the LCD to a 5V power source. If your BeagleBone Black can provide 5V power, you can use it directly. Otherwise, you may need an external power supply. Connect the VO (contrast adjustment) pin to a potentiometer to adjust the contrast of the display.
2. Control Pins: Connect the RS (Register Select) pin of the LCD to a GPIO pin on the BeagleBone Black. This pin is used to select between instruction register and data register. Connect the RW (Read/Write) pin to ground, as we will mainly write data to the display. Connect the E (Enable) pin to another GPIO pin on the BeagleBone Black. This pin is used to latch the data into the display.
3. Data Pins: You can choose to connect the LCD in either 4 - bit or 8 - bit mode. In 4 - bit mode, connect the D4 - D7 pins of the LCD to four GPIO pins on the BeagleBone Black. In 8 - bit mode, connect all D0 - D7 pins to eight GPIO pins. 4 - bit mode is more common as it uses fewer GPIO pins.

Software Setup

Once the hardware is connected, we need to write software to control the LCD display. We can use Python, which has libraries that make it easy to interact with the GPIO pins on the BeagleBone Black.

Here is a simple Python code example to display a message on a 16x2 LCD display in 4 - bit mode:

import Adafruit_BBIO.GPIO as GPIO
import time

# Define GPIO pins for LCD control
RS = "P8_7"
E = "P8_8"
D4 = "P8_9"
D5 = "P8_10"
D6 = "P8_11"
D7 = "P8_12"

# Function to send a 4 - bit nibble to the LCD
def lcd_send_nibble(nibble):
    GPIO.output(D4, (nibble & 0x01) == 0x01)
    GPIO.output(D5, (nibble & 0x02) == 0x02)
    GPIO.output(D6, (nibble & 0x04) == 0x04)
    GPIO.output(D7, (nibble & 0x08) == 0x08)
    GPIO.output(E, GPIO.HIGH)
    time.sleep(0.0001)
    GPIO.output(E, GPIO.LOW)

# Function to send a byte to the LCD
def lcd_send_byte(byte, rs):
    GPIO.output(RS, rs)
    high_nibble = (byte >> 4) & 0x0F
    low_nibble = byte & 0x0F
    lcd_send_nibble(high_nibble)
    lcd_send_nibble(low_nibble)
    time.sleep(0.0005)

# Function to initialize the LCD
def lcd_init():
    GPIO.setup(RS, GPIO.OUT)
    GPIO.setup(E, GPIO.OUT)
    GPIO.setup(D4, GPIO.OUT)
    GPIO.setup(D5, GPIO.OUT)
    GPIO.setup(D6, GPIO.OUT)
    GPIO.setup(D7, GPIO.OUT)

    # Initialize LCD in 4 - bit mode
    time.sleep(0.05)
    lcd_send_nibble(0x03)
    time.sleep(0.005)
    lcd_send_nibble(0x03)
    time.sleep(0.0005)
    lcd_send_nibble(0x03)
    lcd_send_nibble(0x02)

    lcd_send_byte(0x28, GPIO.LOW)  # 4 - bit mode, 2 lines, 5x8 dots
    lcd_send_byte(0x0C, GPIO.LOW)  # Display on, cursor off
    lcd_send_byte(0x06, GPIO.LOW)  # Increment cursor
    lcd_send_byte(0x01, GPIO.LOW)  # Clear display
    time.sleep(0.002)

# Function to display a string on the LCD
def lcd_display_string(string):
    for char in string:
        lcd_send_byte(ord(char), GPIO.HIGH)


# Main program
if __name__ == "__main__":
    try:
        lcd_init()
        lcd_display_string("Hello, BeagleBone!")
        while True:
            pass
    except KeyboardInterrupt:
        GPIO.cleanup()

This code first initializes the GPIO pins on the BeagleBone Black. Then it initializes the LCD display in 4 - bit mode. Finally, it displays a message on the LCD.

Advanced Usage

You can do more than just display a simple message on the LCD. For example, you can display dynamic data such as sensor readings. You can also create multi - line displays and use custom characters.

To display dynamic data, you can modify the lcd_display_string function to update the display with new data at regular intervals. For example, if you have a temperature sensor connected to the BeagleBone Black, you can read the temperature value and display it on the LCD.

import Adafruit_BBIO.GPIO as GPIO
import time
import random  # For simulating sensor data

# Define GPIO pins for LCD control
RS = "P8_7"
E = "P8_8"
D4 = "P8_9"
D5 = "P8_10"
D6 = "P8_11"
D7 = "P8_12"

# Function to send a 4 - bit nibble to the LCD
def lcd_send_nibble(nibble):
    GPIO.output(D4, (nibble & 0x01) == 0x01)
    GPIO.output(D5, (nibble & 0x02) == 0x02)
    GPIO.output(D6, (nibble & 0x04) == 0x04)
    GPIO.output(D7, (nibble & 0x08) == 0x08)
    GPIO.output(E, GPIO.HIGH)
    time.sleep(0.0001)
    GPIO.output(E, GPIO.LOW)

# Function to send a byte to the LCD
def lcd_send_byte(byte, rs):
    GPIO.output(RS, rs)
    high_nibble = (byte >> 4) & 0x0F
    low_nibble = byte & 0x0F
    lcd_send_nibble(high_nibble)
    lcd_send_nibble(low_nibble)
    time.sleep(0.0005)

# Function to initialize the LCD
def lcd_init():
    GPIO.setup(RS, GPIO.OUT)
    GPIO.setup(E, GPIO.OUT)
    GPIO.setup(D4, GPIO.OUT)
    GPIO.setup(D5, GPIO.OUT)
    GPIO.setup(D6, GPIO.OUT)
    GPIO.setup(D7, GPIO.OUT)

    # Initialize LCD in 4 - bit mode
    time.sleep(0.05)
    lcd_send_nibble(0x03)
    time.sleep(0.005)
    lcd_send_nibble(0x03)
    time.sleep(0.0005)
    lcd_send_nibble(0x03)
    lcd_send_nibble(0x02)

    lcd_send_byte(0x28, GPIO.LOW)  # 4 - bit mode, 2 lines, 5x8 dots
    lcd_send_byte(0x0C, GPIO.LOW)  # Display on, cursor off
    lcd_send_byte(0x06, GPIO.LOW)  # Increment cursor
    lcd_send_byte(0x01, GPIO.LOW)  # Clear display
    time.sleep(0.002)

# Function to display a string on the LCD
def lcd_display_string(string):
    for char in string:
        lcd_send_byte(ord(char), GPIO.HIGH)


# Main program
if __name__ == "__main__":
    try:
        lcd_init()
        while True:
            temperature = random.randint(20, 30)  # Simulating temperature reading
            message = f"Temp: {temperature} C"
            lcd_send_byte(0x01, GPIO.LOW)  # Clear display
            time.sleep(0.002)
            lcd_display_string(message)
            time.sleep(2)
    except KeyboardInterrupt:
        GPIO.cleanup()

Conclusion

Integrating an LCD character display with a BeagleBone Black is a straightforward process. With the right hardware connection and software programming, you can create useful and interactive displays. As a supplier of LCD character displays, we offer a wide range of products that are suitable for use with the BeagleBone Black. If you are interested in purchasing LCD character displays for your projects, please contact us for more information and to start a procurement negotiation. We are committed to providing high - quality products and excellent customer service.

References

• Adafruit BeagleBone GPIO Library Documentation
• Hitachi HD44780 LCD Controller Datasheet