In our last project, I shown you how to use one digit 7 segment LED display. In this one, I will show you how to use all 4 digits. I will be using the class i created in our last tutorial.
As you might notice, all four digits are controlled by the same LED inputs (a, b, c... ,f, g), how are we going to display different number on each digit? Actually, we can disable the previous digit before we display the next one. If we do this quick enough, human eyes will not be able to tell the difference.
Let's connect "1Y" to one of the digital output instead of ground, so we can disconnect the circuit to disable LEDs if we want by raising voltage. For example, to display '1' on first digit, we then disable it and display '2' on the second digit, we can make the digital output connected to "1Y" "HIGH", display '2', and make digital output connected to "2Y" LOW.
I have updated the class to support displaying multiple digit numbers up to 9999. for example you can display the number '1234 easily by the 2 lines:
LEDDisplay disp;disp.DisplayNumber(1234);
Easy! See my source code for how to implement.
Here is the Circuit Diamgram: (see blue lines for changes from the last one )
Source Code for the class:
#include "WProgram.h" //standard types and constants of the Arduino language enum Num { NOTHING = -1, ZERO = 0, ONE = 1, TWO = 2, THREE = 3, FOUR = 4, FIVE = 5, SIX = 6, SEVEN = 7, EIGHT = 8, NINE = 9, DECIMAL_POINT = 10}; // 10 means decimal point, -1 means nothing is being displayed class LEDDisplay { public: Num displaying; // indicate which number is being displayed private: int aPin; // these are the output pins int bPin; int cPin; int dPin; int ePin; int fPin; int gPin; int dpPin; int y1Pin; // these are used to control display which digit int y2Pin; int y3Pin; int y4Pin; public: LEDDisplay(); // constructor with default output pins LEDDisplay(int a, int b, int c, int d, int e, int f, int g, int dp, int y1, int y2, int y3, int y4); // constructor with specified output pins void DisplayDigit (Num digit); void DisplayNumber (int number); }; |
#include "Seven_Seg_LED_Display.h" LEDDisplay::LEDDisplay () { displaying = NOTHING; for (int outputPin = 1; outputPin <= 8; outputPin++) pinMode(outputPin, OUTPUT); // LED pin aPin = 1; bPin = 2; cPin = 3; dPin = 4; ePin = 5; fPin = 6; gPin = 7; dpPin = 8; for (int yPin = 10; yPin <= 13; yPin++) pinMode(yPin, OUTPUT); // control to display which digit y1Pin = 10; y2Pin = 11; y3Pin = 12; y4Pin = 13; } LEDDisplay::LEDDisplay(int a, int b, int c, int d, int e, int f, int g, int dp, int y1, int y2, int y3, int y4) { displaying = NOTHING; pinMode(aPin = a, OUTPUT); pinMode(bPin = b, OUTPUT); pinMode(cPin = c, OUTPUT); pinMode(dPin = d, OUTPUT); pinMode(ePin = e, OUTPUT); pinMode(fPin= f, OUTPUT); pinMode(gPin = g, OUTPUT); pinMode(dpPin = dp, OUTPUT); pinMode(y1Pin = y1, OUTPUT); pinMode(y2Pin = y2, OUTPUT); pinMode(y3Pin = y3, OUTPUT); pinMode(y4Pin = y4, OUTPUT); } void LEDDisplay::DisplayDigit (Num digit){ displaying = digit; switch (digit) { case ZERO: digitalWrite(aPin, HIGH); digitalWrite(bPin, HIGH); digitalWrite(cPin, HIGH); digitalWrite(dPin, HIGH); digitalWrite(ePin, HIGH); digitalWrite(fPin, HIGH); digitalWrite(gPin, LOW); digitalWrite(dpPin, LOW); break; case ONE: digitalWrite(aPin, LOW); digitalWrite(bPin, HIGH); digitalWrite(cPin, HIGH); digitalWrite(dPin, LOW); digitalWrite(ePin, LOW); digitalWrite(fPin, LOW); digitalWrite(gPin, LOW); digitalWrite(dpPin, LOW); break; case TWO: digitalWrite(aPin, HIGH); digitalWrite(bPin, HIGH); digitalWrite(cPin, LOW); digitalWrite(dPin, HIGH); digitalWrite(ePin, HIGH); digitalWrite(fPin, LOW); digitalWrite(gPin, HIGH); digitalWrite(dpPin, LOW); break; case THREE: digitalWrite(aPin, HIGH); digitalWrite(bPin, HIGH); digitalWrite(cPin, HIGH); digitalWrite(dPin, HIGH); digitalWrite(ePin, LOW); digitalWrite(fPin, LOW); digitalWrite(gPin, HIGH); digitalWrite(dpPin, LOW); break; case FOUR: digitalWrite(aPin, LOW); digitalWrite(bPin, HIGH); digitalWrite(cPin, HIGH); digitalWrite(dPin, LOW); digitalWrite(ePin, LOW); digitalWrite(fPin, HIGH); digitalWrite(gPin, HIGH); digitalWrite(dpPin, LOW); break; case FIVE: digitalWrite(aPin, HIGH); digitalWrite(bPin, LOW); digitalWrite(cPin, HIGH); digitalWrite(dPin, HIGH); digitalWrite(ePin, LOW); digitalWrite(fPin, HIGH); digitalWrite(gPin, HIGH); digitalWrite(dpPin, LOW); break; case SIX: digitalWrite(aPin, HIGH); digitalWrite(bPin, LOW); digitalWrite(cPin, HIGH); digitalWrite(dPin, HIGH); digitalWrite(ePin, HIGH); digitalWrite(fPin, HIGH); digitalWrite(gPin, HIGH); digitalWrite(dpPin, LOW); break; case SEVEN: digitalWrite(aPin, HIGH); digitalWrite(bPin, HIGH); digitalWrite(cPin, HIGH); digitalWrite(dPin, LOW); digitalWrite(ePin, LOW); digitalWrite(fPin, LOW); digitalWrite(gPin, LOW); digitalWrite(dpPin, LOW); break; case EIGHT: digitalWrite(aPin, HIGH); digitalWrite(bPin, HIGH); digitalWrite(cPin, HIGH); digitalWrite(dPin, HIGH); digitalWrite(ePin, HIGH); digitalWrite(fPin, HIGH); digitalWrite(gPin, HIGH); digitalWrite(dpPin, LOW); break; case NINE: digitalWrite(aPin, HIGH); digitalWrite(bPin, HIGH); digitalWrite(cPin, HIGH); digitalWrite(dPin, LOW); digitalWrite(ePin, LOW); digitalWrite(fPin, HIGH); digitalWrite(gPin, HIGH); digitalWrite(dpPin, LOW); break; case DECIMAL_POINT: digitalWrite(aPin, LOW); digitalWrite(bPin, LOW); digitalWrite(cPin, LOW); digitalWrite(dPin, LOW); digitalWrite(ePin, LOW); digitalWrite(fPin, LOW); digitalWrite(gPin, LOW); digitalWrite(dpPin, HIGH); break; default: digitalWrite(aPin, LOW); digitalWrite(bPin, LOW); digitalWrite(cPin, LOW); digitalWrite(dPin, LOW); digitalWrite(ePin, LOW); digitalWrite(fPin, LOW); digitalWrite(gPin, LOW); digitalWrite(dpPin, LOW); } } void LEDDisplay::DisplayNumber (int number){ int temp; // determine the digits of the number int thousand = number/1000; temp = number%1000; int hundred = temp/100; temp = temp%100; int ten = temp/10 ; temp = temp%10; int unit = temp; // determine what to display (note I cast int to Num) if (thousand == 0){ if (hundred == 0){ if (ten == 0){ digitalWrite(y1Pin, HIGH); digitalWrite(y2Pin, HIGH); digitalWrite(y3Pin, HIGH); digitalWrite(y4Pin, LOW); DisplayDigit((Num)unit); delay(5); } else { digitalWrite(y1Pin, HIGH); digitalWrite(y2Pin, HIGH); digitalWrite(y3Pin, LOW); DisplayDigit((Num)ten); delay(5); digitalWrite(y3Pin, HIGH); digitalWrite(y4Pin, LOW); DisplayDigit((Num)unit); delay(5); digitalWrite(y4Pin, HIGH); } } else{ digitalWrite(y1Pin, HIGH); digitalWrite(y2Pin, LOW); DisplayDigit((Num)hundred); delay(5); digitalWrite(y2Pin, HIGH); digitalWrite(y3Pin, LOW); DisplayDigit((Num)ten); delay(5); digitalWrite(y3Pin, HIGH); digitalWrite(y4Pin, LOW); DisplayDigit((Num)unit); delay(5); digitalWrite(y4Pin, HIGH); } } else{ digitalWrite(y1Pin, LOW); DisplayDigit((Num)thousand); delay(5); digitalWrite(y1Pin, HIGH); digitalWrite(y2Pin, LOW); DisplayDigit((Num)hundred); delay(5); digitalWrite(y2Pin, HIGH); digitalWrite(y3Pin, LOW); DisplayDigit((Num)ten); delay(5); digitalWrite(y3Pin, HIGH); digitalWrite(y4Pin, LOW); DisplayDigit((Num)unit); delay(5); digitalWrite(y4Pin, HIGH); } } |
Code for the main program:
| /* Oscar's project how to use 7-seg LED display */ #include "Seven_Seg_LED_Display.h" const int buttonPin = 9; // the number of the pushbutton pin int buttonState = 0; // variable for reading the pushbutton status int beingPressed = 0; // make sure we only respond to button once when it first being pressed LEDDisplay disp; // I made a mistake declaring this inside 'loop', but in which case, it can't remember what it displayed previously int state = 0; void setup() { // initialize the pushbutton pin as an input: pinMode(buttonPin, INPUT); } void loop() { buttonState = digitalRead(buttonPin); /* if (state == 0) disp.DisplayNumber(102); else disp.DisplayNumber(523); if ((buttonState == HIGH) && (beingPressed == LOW)) { state++; } beingPressed = buttonState; */ switch (state){ case 0: disp.DisplayNumber(0); break; case 1: disp.DisplayNumber(1234); break; case 2: disp.DisplayNumber(523); break; case 3: disp.DisplayNumber(70); break; case 4: disp.DisplayNumber(3205); break; case 5: disp.DisplayNumber(5268); break; case 6: disp.DisplayNumber(12); break; case 7: disp.DisplayNumber(555); break; default: disp.DisplayNumber(8888); } if ((buttonState == HIGH) && (beingPressed == LOW)){ if (++state == 9) state = 0; } beingPressed = buttonState; } |
