# Tutorial: 7-Segment Display

##

## Using 7-Segment Display in STM32F4

We will learn how to display a decimal number (0\~9) on a 7-segment display

* Inputs:
  * Decimal number : 0\~9
  * Binary: 4-bit numbers \[D C B A] // (0000\~ 1001)
* Output:
  * 7-segment decoder: 7-bit numbers ( a to g)
  * 7-segment display: decimal number 0\~9

####

We will learn how to configure the 7-segment display for different options

#### Option 1. With 7-segment decoder

#### Option 2. Without using 7-segment decoder

#### Option 3. Without using 7-segment decoder on JKIT evaluation board

####

## Circuit Description

### Hardware Specification

* 7-segment display: common anode (5101ASR)
* 7-segment decoder: [74LS47N (datasheet download)](https://pdf1.alldatasheet.com/datasheet-pdf/download/5724/MOTOROLA/SN74LS47N.html)

### 7-segment display (5101ASR)

For more detail information about 7 segment display - [click here](https://www.electronics-tutorials.ws/combination/comb_6.html)

* Common anode: (common pin is connected to VCC)
* Giving ‘LOW’ to the pin -> LED ON
* Needs a load resistor for each pin(led)

Check the difference between the common cathode and common anode.

> We will use common anode.

![image](https://user-images.githubusercontent.com/91526930/192942501-63b87284-7c94-4863-8200-106baa02b907.png)

### BCD 7-segment decoder

Model: [74LS47N (datasheet download)](https://pdf1.alldatasheet.com/datasheet-pdf/download/5724/MOTOROLA/SN74LS47N.html)

* All output pins are active LOW

<figure><img src="/files/iMB8Sg6uRSuRvJcOiBEC" alt="" width="375"><figcaption></figcaption></figure>

<figure><img src="/files/8jw3yPfrJpkYyuiuAqJ4" alt="" width="563"><figcaption></figcaption></figure>

###

### Array resistor (B331J)

![array resistor](https://user-images.githubusercontent.com/91526930/192131231-c6ae1c48-a236-43f8-9577-010ccd46eccc.png)

## Option 1. Connecting with a BCD 7-segment decoder

<figure><img src="/files/9w4HPg5TONOcPU4nXj5R" alt=""><figcaption></figcaption></figure>

###

###

## Option 2. Connecting without a 7-segment decoder

### Circuit Configuration

![image](https://github.com/user-attachments/assets/5ca0e7ba-2620-4615-9aea-07aaf7e2aadb)

![circuit on breadbord](https://user-images.githubusercontent.com/91526930/192194707-c62df336-9869-4de1-9d72-cb2355166989.png)

### Example Code

Download the tutorial code

* `TU_GPIO_LED_7segment_student.c` [Click here for download](https://github.com/ykkimhgu/EC-student/tree/main/tutorial/tutorial-student)
* Program a function that works as a 7-segment decoder

```cpp
#include "stm32f4xx.h"
#include "ecRCC2.h"
#include "ecGPIO2.h"

void setup(void);
	
int main(void) {	
	// Initialiization --------------------------------------------------------
	setup();
	
	// Inifinite Loop ----------------------------------------------------------
	while(1){
		GPIO_write(PA_5, LOW);
		GPIO_write(PA_6, LOW);
		GPIO_write(PA_7, HIGH);
		GPIO_write(PB_6, HIGH);
		GPIO_write(PC_7, HIGH);
		GPIO_write(PA_9, LOW);
		GPIO_write(PA_8, LOW);
		GPIO_write(PB_10, LOW);
	}
}

void setup(void){
	RCC_HSI_init();
	GPIO_init(PA_5, OUTPUT);
	GPIO_init(PA_6, OUTPUT);
	GPIO_init(PA_7, OUTPUT);
	GPIO_init(PB_6, OUTPUT);
	GPIO_init(PC_7, OUTPUT);
	GPIO_init(PA_9, OUTPUT);
	GPIO_init(PA_8, OUTPUT);
	GPIO_init(PB_10, OUTPUT);
}
```

## Option 3. Without using a 7-segment decoder on JKIT evaluation board

### Circuit Configuration

JKIT - Nucleo 64: [link](https://www.devicemart.co.kr/goods/view?no=14123215\&srsltid=AfmBOooT3zgaxGXZ_q0fvy4uZxHesTbwpqNprE6P3YXMk9V0EGoGrhLM)

<figure><img src="https://raw.githubusercontent.com/LeeJunjae1/EC_22000573/main/img/connect.jpg" alt="" width="375"><figcaption></figcaption></figure>

<div align="center"><img src="https://raw.githubusercontent.com/LeeJunjae1/EC_22000573/main/img/7seg.png" alt="config"> <img src="https://raw.githubusercontent.com/LeeJunjae1/EC_22000573/main/img/LED.png" alt="LED Choose"></div>

* There are four 7-Segment Displays. You need to choose which one to use.
* There is NO BCD decoder, you need to connect 7-segment display without using decoder.

{% hint style="info" %}
**7-segments display are Common Cathode: Giving 'High' to the pin -> LED on**
{% endhint %}

| 1. Digital Out: 7-Segment display number               | 2. Digital Out: Select 7-Segment display |
| ------------------------------------------------------ | ---------------------------------------- |
| Digital Out                                            | Digital Out                              |
| PB\_7, PB\_6, PB\_5, PB\_4, PB\_3, PB\_2, PB\_1, PB\_0 | PC\_3, PC\_4, PA\_11, PA\_10             |
| Push-Pull                                              | Push-Pull                                |

#### Example Code

```c
PinName_t led[8]={PB_7, PB_6, PB_5, PB_4, PB_3, PB_2, PB_1, PB_0};


//each led that has to light up gets a 1, every other led gets a 0
//its in order of the DigitalOut Pins above
int number[11][8]={
                    {1,1,1,0,1,1,1,0},          //zero
                    {0,0,1,0,0,1,0,0},          //one
                    {1,0,1,1,1,0,1,0},          //two
                    {1,0,1,1,0,1,1,0},          //three
                    {0,1,1,1,0,1,0,0},          //four
                    {1,1,0,1,0,1,1,0},          //five
                    {1,1,0,1,1,1,1,0},          //six
                    {1,0,1,0,0,1,0,0},          //seven
                    {1,1,1,1,1,1,1,0},          //eight
                    {1,1,1,1,0,1,1,0},          //nine
                    {0,0,0,0,0,0,0,1}          //dot
                  };


        
//display shows the number in this case 6
int num=6;
for (int i=0; i<8; i++)
    led[i] = number[num][i];

```

## Exercise

Create a simple code that can Select and Display a decimal number (0\~9) on 7-segment display (JKIT - Nucleo 64)

* Display Selection and Number
  * (1) Selection of the display: 0\~3
  * (2) Decimal Number to display: 0\~9
* Output Display:
  * 7-segment displaying a decimal number: 0\~9

{% hint style="info" %}
If you want to display multiple 7-segment displays, you need to use a very short delay to display multiple numbers
{% endhint %}

**Exercise Code**

```c
#include "stm32f4xx.h"
#include "ecGPIO2.h"
#include "ecRCC2.h"


// Initialize 7 DOUT pins for 7 segment leds
void seven_seg_FND_init(void); 

// Select display: 0 to 3
// Display a number 0 - 9 only
void seven_seg_FND_display(uint8_t  num, uint8_t select);


void setup(void){
    // Intialize System Clock
    RCC_HSI_init();
    
    // Intialize DOUT Pins      
    // and Others
    // [YOUR CODE GOES HERE]    
    seven_seg_FND_init(); 
};

int main(void) {
    setup();
    uint8 numDisplay=8;
    uint8 selectFND=0;

    while (1) {
        seven_seg_FND_display(numDisplay,selectFND);
    }
}


// Initialize DOUT pins for 7 segment leds
void seven_seg_FND_init(void){	
    //pin name array
    PinName_t pinsFND[12]={PB_7, PB_6, PB_5, PB_4, PB_3, PB_2, PB_1, PB_0, PC_3, PC_4, PA_11, PA_10};
	
    //Iteratively initializing DOUT pins for pinsFND
    // for (int i=0;i<8;i++)
    //    { initialize each pin as output};
    // [YOUR CODE GOES HERE]
    // [YOUR CODE GOES HERE]
}

// Select display: 0 to 3
// Display a number 0 - 9 only
void seven_seg_FND_display(uint8_t  num, uint8_t select){
    // [YOUR CODE GOES HERE]    
    // [YOUR CODE GOES HERE]        
}

```


---

# Agent Instructions: Querying This Documentation

If you need additional information that is not directly available in this page, you can query the documentation dynamically by asking a question.

Perform an HTTP GET request on the current page URL with the `ask` query parameter:

```
GET https://ykkim.gitbook.io/ec/ec-course/tutorial/tutorial-7segment-display.md?ask=<question>
```

The question should be specific, self-contained, and written in natural language.
The response will contain a direct answer to the question and relevant excerpts and sources from the documentation.

Use this mechanism when the answer is not explicitly present in the current page, you need clarification or additional context, or you want to retrieve related documentation sections.