Seven-Segment Shield

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arduino shields 7-segment-shield

Using the Seven-Segment Shield's display, EEPROM, temperature sensor, and RGB LED with Arduino

The Seven-Segment Shield

The shield is available here. It has the following onboard devices:


The shield uses Arduino pins D3, D5, D6 (for the LED), A4, and A5 (for I2C), so they cannot be used for anything else.


This project uses my SevenSegmentShield library. Download the library in Zip format

All example code is under File > Examples > SevenSegmentShield.

Displaying Digits and Letters

The Display > CycleDigits example displays the digits 0-9 on each segment.

The Display > DisplayChars example directly writes to the segments, displaying “-AbC”.

   This sketch displays characters such as letters and dashes on the segments.
   Created on 9 April 2020 by Aidan Sun

#include <SevenSegmentShield.h>
#include <Wire.h>

Display ds;

void setup() {
  ds.begin(); // Initialize display

void loop() {
  // Display a dash on segment 1
  ds.writeDigitData(4, 64); // digit number, data to write

  // Display the letters A-C on segments 2-4
  ds.writeDigitData(3, 119); // A
  ds.writeDigitData(2, 124); // B
  ds.writeDigitData(1, 57);  // C

Initializing the Display

Wire.begin must be called before using any of the shield’s I2C devices to intialize the communication bus.

The begin method of the Display class sets the default brightness for the LEDs. (See “Cycling Brightness”)

Displaying on a Single Digit

Both methods below take the following parameter:

digit: The digit to write to, from 1 (rightmost on the shield) to 4 (leftmost)

writeDigit: Displays a digit. Takes the following parameters:

  1. digit
  2. value: The numeric value to show on the digit (0-9)
  3. decimalPoint: If the digit’s decimal point is shown (true to show, false to hide)

writeDigitData: Controls the individual segments on a digit.

  1. digit
  2. value: 1-byte integer containing the segments to display
Segment Values

Segment values may be added together to display them together:

Segment values

Clearing the Display

clear: Turns off all segments on the display. Takes no parameters.

Displaying Integers

Integers can also be displayed on the shield. An example is at Display > DisplayNum.

   This sketch displays numbers on the shield with displayInt().
   Created on 9 April 2020 by Aidan Sun

#include <SevenSegmentShield.h>
#include <Wire.h>

Display ds;

void setup() {

void loop() {
  int number = random(-999, 10000); // Generate a random number from -999 to 9999
  ds.displayInt(number); // Display the number
  delay(1000); // Wait to let the user see the number

The code above randomly generates integers and displays them with the function below:

displayInt: Shows an integer on the entire display.

  1. number: Number to show (-999 to 9999)

Cycling Brightness

The brightness of the display can be adjusted by changing the amount of current the LEDs receive. An example is at Display > CycleBrightness.

   This sketch cycles through the brightness for the segments.
   The possible values are 3mA, 6mA, 9mA, 12mA, 18mA, and 21mA.
   Created on 8 April 2020 by Aidan Sun

#include <SevenSegmentShield.h>
#include <Wire.h>

Display ds;

void setup() {
  ds.displayInt(8888); // Display the number 8888

void loop() {

  for (int i = 0; i < 6; i++) {
    delay(500); // 1/2 second delay

The code loops through each possible current value, passing each to the function:

writeBrightness: Sets the brightness of the seven-segment display. The default current is 12 mA.

  1. brightness: Current value to determine brightness. Possible values are:

Using the EEPROM Chip

The 24LC128 chip on the shield can hold 128 kB of data. The EEPROM > ReadWrite example demonstrates performing I/O on the addresses of the EEPROM.

Reading and Writing Memory

The methods below are part of the MemoryChip class, which represents the onboard 24LC128. They share the following parameter:

address: The address to read or write from

readByte: Returns the byte at the specified memory address.

  1. address

writeByte: Writes the given byte to the specified memory address.

  1. address
  2. data: Byte to write


After writing to the EEPROM, insert a short delay (such as 5 ms in the example) to prevent the loss of communication data.

Controlling the LED

The shield’s RGB LED is connected to three PWM pins on the Arduino. The LED > CycleColors example uses PWM to display different colors.

   This sketch cycles through 48 colors on the LED.
   Created on 10 April 2020 by Aidan Sun

#include <SevenSegmentShield.h>

RgbLed led;

const long COLORS[48] = {
  0xFF2000, 0xFF4000, 0xFF6000, 0xFF8000, 0xFFA000, 0xFFC000, 0xFFE000, 0xFFFF00,
  0xE0FF00, 0xC0FF00, 0xA0FF00, 0x80FF00, 0x60FF00, 0x40FF00, 0x20FF00, 0x00FF00,
  0x00FF20, 0x00FF40, 0x00FF60, 0x00FF80, 0x00FFA0, 0x00FFC0, 0x00FFE0, 0x00FFFF,
  0x00E0FF, 0x00C0FF, 0x00A0FF, 0x0080FF, 0x0060FF, 0x0040FF, 0x0020FF, 0x0000FF,
  0x2000FF, 0x4000FF, 0x6000FF, 0x8000FF, 0xA000FF, 0xC000FF, 0xE000FF, 0xFF00FF,
  0xFF00E0, 0xFF00C0, 0xFF00A0, 0xFF0080, 0xFF0060, 0xFF0040, 0xFF0020, 0xFF0000

const int NUM_OF_COLORS = 48;

void setup() {}

void loop() {
  for (int i = 0; i < NUM_OF_COLORS; i++) {
    long currentColor = COLORS[i];
    led.displayHexColor(currentColor); // Display the color

  // Turn off the LED

Hex and RGB Colors

The example above defines 48 hex colors. Each color is an integer with 8 bits of red (leftmost bits), green, and blue (rightmost bits) values.

displayHexColor: Displays a color on the LED given in hexadecimal format.

  1. hh: Color

displayRGBColor: Displays a color on the LED given with individual red, green, and blue components.

  1. r: 8-bit red value
  2. g: 8-bit green value
  3. b: 8-bit blue value

turnOff: Turns the LED off. Takes no parameters.

Reading from the TMP75

The TMP75 > Thermometer example uses the shield to create a thermometer. The temperature is displayed on the segments, and the LED changes color accordingly.

All TMP75 functions are contained inside a class called TMP75.

Initializing the TMP75

begin: Initializes the TMP75 and configures it to 12-bit resolution.

Reading the Temperature

read: Returns the temperature read by the TMP75 in degrees Celsius.