By dave | May 4, 2015

Using the LEDDisplay library

LEDDisplay is an easy to use library that makes light work of multi-digit 7segment displays. If you need help building the circuit or understanding the concepts, then refer to this guide: Arduino multiple digit, 7 segment display tutorial.

Answering questions and getting help

Get help from the community forum for LEDDisplay
You can also contact us about commercial support on LEDDisplay

Setting up the LEDDisplay library

Before using any methods from the library, and usually in the global scope (outside of any function) you need to include the header file and initialise the library.

#include <leddisplay.h>

LEDDisplay display(startingPin, commonHigh, [numberOfDigits optional]);
  • startingPin: refers to the first pin where the A pin of the 7segment display is connected, others must be sequential (eg segment B on startingPin + 1 etc).
  • commonHigh: true if the common pins need to be HIGH (5V) to switch on.
  • numberOfDigits: the number of digits, defaults to 4.

Should you wish to change brightness,

display.setBrightness(newBrightness);
  • newBrightness: between 0 and 3.

Ways to refresh the display (choose only one option)

Option 1: If you want to use the interrupt support (then you don’t need to worry about refreshing the display 100 times a second)

display.startInterrupt();

Option 2: If you don’t want to use interrupts, you must refresh the display between 50 and 100 times a second to avoid flicker, calling this method.

display.isr_display();

Option 3: Should you be using IoAbstraction library already then just do the following:

    // Only for users of IoAbstraction library
    taskManager.scheduleAtFixedRate(10, [] {
        display.isr_display();
    });

Rendering values onto the display

At this point the LED display will be initialised, but will not display a value. You can populate the display in several ways.

For displaying integer values:

display.setValueDec(value, [optional zeroPad]);
display.setValueHex(value);

Where

  • value: the value to be display
  • zeroPad: true if you want to pad with zeros

For displaying floating points:

display.setValueFloat(value, precision, [optional zeroPad]);

Where:

  • value: the value to be display
  • precision: the number of decimal places
  • zeroPad: true if you want to pad with zeros

Setting characters directly

display.setValueRaw(digit, character, dpOn);

Where:

  • digit: the digit to be updated
  • character: the character to write into the digit (see the character set lower down)
  • dpOn: true to show the decimal point, otherwise false

Setting a few of the digits to a numeric value

display.setNumeric(value, base, startDigit, extendBy);

Where:

  • value: the value to be displayed
  • base: the base of the numbers to be displayed (decimal: 10, hex: 16)
  • startDigit: starting digit position
  • extendBy: the number of extra digits to include

A few examples of advanced usage

// Example 1: put character onto the display directly at position 1
display.setValueRaw(1, 0x12);

// Example 2: put character onto the display directly at position 1 and set the DP on.
display.setValueRaw(i, 0x14, true);

// Example 3: write the integer 23 as decimal into digits 1 and 2
display.setNumeric(23, 10, 1, 1); 

Character set for setValueRaw

When using setValueRaw(..) these are the values that can be displayed, use the Value field in the call. For example to display the digit ‘F’ in position 1 setValueRaw(1, 0x0F);

Value Character Binary (ABCDEFG)
0x00 ‘0’ 0b1111110
0x01 ‘1’ 0b0110000
0x02 ‘2’ 0b1101101
0x03 ‘3’ 0b1111001
0x04 ‘4’ 0b0110011
0x05 ‘5’ 0b1011011
0x06 ‘6’ 0b1011111
0x07 ‘7’ 0b1110000
0x08 ‘8’ 0b1111111
0x09 ‘9’ 0b1111011
0x0A ‘a’ 0b1110111
0x0B ‘b’ 0b0011111
0x0C ‘c’ 0b1001110
0x0D ’d’ 0b0111101
0x0E ‘e’ 0b1101111
0x0F ‘f’ 0b1000111
0x10 ‘g’ 0b1111011
0x11 ‘h’ 0b0110111
0x12 ‘i’ 0b0110000
0x13 ‘j’ 0b0111000
0x14 ‘l’ 0b0001110
0x15 ‘n’ 0b0010101
0x16 ‘o’ 0b0011101
0x17 ‘p’ 0b1100111
0x18 ‘r’ 0b0000101
0x19 ’s’ 0b1011011
0x1A ’t’ 0b0001111
0x1B ‘u’ 0b0011100
0x1C ‘y’ 0b0111011
0x1D ' ' 0b0000000

For more advanced usages see the header file on github: [https://github.com/davetcc/leddisplay/blob/master/LEDDisplay.h]

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