Using a 4 Digit 7 Segment display

The 4 Digit 7 segment display I used had 4 common anodes (1 for each digit) and 8 connecting pins for each segment as well as decimal point.

The top row of pins were 12 (anode 1st digit), 11, 10, 9 (anode 2nd digit), 8 (anode 3rd digit), 7, the bottom row of pins were 1, 2, 3, 4, 5, 6 (anode 4th digit).

Here's a diagram of the pin layout.

![](http://www.jamesrobertson.eu/r/svg/2016/feb/25/4-digit-7-segment.svg)

## Example code

    /* SevSeg Counter Example
     
     Copyright 2014 Dean Reading
     
     Licensed under the Apache License, Version 2.0 (the "License");
     you may not use this file except in compliance with the License.
     You may obtain a copy of the License at 
     http://www.apache.org/licenses/LICENSE-2.0
     
     Unless required by applicable law or agreed to in writing, software
     distributed under the License is distributed on an "AS IS" BASIS,
     WITHOUT WARRANTIES OR CONDITIONS OF ANY KIND, either express or implied.
     See the License for the specific language governing permissions and
     limitations under the License.
     
     
     This example demonstrates a very simple use of the SevSeg library with a 4
     digit display. It displays a counter that counts up, showing deci-seconds.
     */

    #include "SevSeg.h"

    SevSeg sevseg; //Instantiate a seven segment controller object

    void setup() {
      byte numDigits = 4;   
      byte digitPins[] = {12, 9, 8, 6};
      byte segmentPins[] = {11, 7, 4, 2, 1, 10, 5};

      sevseg.begin(COMMON_ANODE, numDigits, digitPins, segmentPins);
      sevseg.setBrightness(10);

    }

    void loop() {
      static unsigned long timer = millis();
      static int deciSeconds = 0;
      
      if (millis() >= timer) {
        deciSeconds++; // 100 milliSeconds is equal to 1 deciSecond
        timer += 100; 
        if (deciSeconds == 10000) { // Reset to 0 after counting for 1000 seconds.
          deciSeconds=0;
        }
        sevseg.setNumber(deciSeconds, 1);
      }

      sevseg.refreshDisplay(); // Must run repeatedly
    }

    /// END ///

Output:

Here's a short video of the 4 digit 7 segment display counting up from 0
!v[](http://www.jamesrobertson.eu/r/videos/2016/feb/25/7segment-display.ogv)

Note: There's a nuisance factor with digit 1, where segment **A** remains on when it shouldn't.

## Resources

* Seven-segment display https://en.wikipedia.org/wiki/Seven-segment_display
* Arduino Playground - SevenSegmentLibrary http://playground.arduino.cc/Main/SevenSegmentLibrary
* DeanIsMe/SevSeg: Seven segment display controller library for Arduino https://github.com/DeanIsMe/SevSeg
* 7 Segment 4 Digit Super Red LED Display Common Anode http://www.jamesrobertson.eu/cpages/2016/feb/24/7-segment-4-digit-super-red-led-display-common-anode-ebay-co-uk.html

7segment display