LAB: EXTI & SysTick(eval board)

Date: 2025-09-26

Author/Partner:

Github: repository link

Demo Video: Youtube link

PDF version:

Introduction

In this lab, you are required to create two simple programs using interrupt:

(1) displaying the number counting from 0 to 19 with Button Press

(2) counting at a rate of 1 second

You must submit

• LAB Report (*.md & *.pdf)

• Zip source files(main*.c, ecRCC2.h, ecGPIO2.h, ecSysTick2.c etc...).

  • Only the source files. Do not submit project files

Requirement

Hardware

• MCU

  • NUCLEO-F411RE

• Actuator/Sensor/Others:

  • eval board

Software

• PlatformIO, CMSIS, EC_HAL library

Tutorial: STM-Arduino

Tutorial: arduino-stm32 Part1 | ECykkim.gitbook.io

We are going to create a simple program that turns LED(LD2) on triggered by External Interrupt of user button(BT1)/

attachInterrupt()

attachInterrupt(digitalPinToInterrupt(pin), ISR, mode)

• digitalPinToInterrupt(pin): translate the digital pin to the specific interrupt number.

• ISR: a function called whenever the interrupt occurs.

• mode: defines when the interrupt should be triggered. (LOW, CHANGE, RISING, FALLING)

Procedure

1. Create a new project under the directory \EC\lab\LAB_EXTI

2. Open Arduino IDE and Create a new program named as ‘TU_arduino_EXTINT.ino’.

3. Write the following code.

const int btnPin = 3;
const int ledPin =  13; 

int btnState = HIGH;

void setup() {
    pinMode(ledPin, OUTPUT);
    pinMode(btnPin, INPUT_PULLUP);
    attachInterrupt(digitalPinToInterrupt(btnPin), blink, CHANGE);
}

void loop() {
    // blank
}


void blink(){
    btnState = digitalRead(btnPin);

    if (btnState == HIGH)
        digitalWrite(ledPin, LOW);
    else 
        digitalWrite(ledPin, HIGH);
}

The user button pin is PC13, but this pin cannot be used in arduino. So, you should connect PC13 to pinName D3 by using wire.

1. Click on upload button.

2. Whenever the user button(BT1) is pressed (at fall), LED should be ON. When the button is released, the LED should be OFF.

---

Tutorial: STM32F4xx

1.Tutorial: Managing library header files

Read how to manage library header files for MCU register configurations. Apply it in your LAB.

Tutorial: Managing library header files | ECykkim.gitbook.io

2.Tutorial: Custom Initialization

Instead of writing initial setting functions for each registers, you can call a user defined function e.g. MCU_init() for the commonly used default initialization. Follow the tutorial and apply it in your LAB.

Tutorial: Custom initialization | ECykkim.gitbook.io

---

Problem 1: Counting numbers on 7-Segment using EXTI Button

Creating EXTI library

1. Download sample header files:

   ecEXTI2_student.h, ecEXTI2_student.c

2. Rename these files as ecEXTI2.h, ecEXTI2.c

   • You MUST write your name and other information at the top of the library code files.

   • Save these files in your directory EC \include\.

3. Declare and define the following functions in your library ecEXTI2.h

ecEXTI.h

void EXTI_init(PinName_t pinName, int trig_type, int priority);
void EXTI_enable(uint32_t pin);  // mask in IMR
void EXTI_disable(uint32_t pin);  // unmask in IMR
uint32_t  is_pending_EXTI(uint32_t pin);
void clear_pending_EXTI(uint32_t pin);

Procedure

1. Create a new project under the directory \EC\lab\LAB_EXTI

• The project name is “LAB_EXTI”.

• Create a new source file named as “LAB_EXTI.c”

You MUST write your name on the source file inside the comment section.

2. Include your updated library in \EC\include\ to your project.

• ecGPIO2.h, ecGPIO2.c

• ecRCC2.h, ecRCC2.c

• ecEXTI2.h, ecEXTI2.c

1. First, check if every number, 0 to 9, can be displayed properly on each 7-segment (there are a total of 4 7-segment display on the evaluation board).

2. Then, create a code to display the number counting from 0 to 19 and repeating.

   • Count up only by pressing the push button

   • Must use External Interrupt

   • Refer to sample codes

Configuration

Digital In for Button (B1)	Digital Out for FND-7-Segment
Digital In	Digital Out
PA4	PB7,PB6,PB5,PB4,PB3,PB2,PB1,PB0 ('a''h', respectively) PC3,PC4,PA11,PA10 ('LED1''LED4', respectively)
PULL-UP	Push-Pull, No PullUp-PullDown, Medium Speed

Circuit Diagram

You need to include the circuit diagram

image

Discussion

1. We can use two different methods to detect an external signal: polling and interrupt. What are the advantages and disadvantages of each approach?

Answer discussion questions

1. What would happen if the EXTI interrupt handler does not clear the interrupt pending flag? Check with your code

   Answer discussion questions

Code

Your code goes here.

Explain your source code with the necessary comments.

// YOUR MAIN CODE ONLY
// YOUR CODE

Sample Code

#include "ecSTM32F4v2.h"

#define LED_PIN	PA_5
#define BUTTON_PIN PC_13

// Initialiization 
void setup(void)
{
	RCC_PLL_init();
	SysTick_init();
	GPIO_init(LED_PIN, OUTPUT);
	GPIO_init(BUTTON_PIN, INPUT);
	GPIO_pupd(BUTTON_PIN, EC_PD);
	// Priority Highest(0) External Interrupt 
	EXTI_init(BUTTON_PIN, FALL, 0);
}

int main(void) {
	setup();
	while (1) {}
}

//EXTI for Pin 13
void EXTI15_10_IRQHandler(void) {
	if (is_pending_EXTI(BUTTON_PIN)) {
		LED_toggle();
	clear_pending_EXTI(BUTTON_PIN); 
	}
}

Results

Experiment images and results go here

Show experiment images /results

Add demo video link

Problem 2: Counting numbers on 7-Segment using SysTick

Display the number 0 to 9 on the 7-segment LED at the rate of 1 sec.

After displaying up to 9, then it should display ‘0’ and continue counting.

When the button is pressed, the number should be reset ‘0’ and start counting again.

SysTick Library

1. Download sample header files: ecSysTick_student.h, ecSysTick_student.c

2. Rename these files as ecSysTick2.h, ecSysTick2.c

   • You MUST write your name and other information at the top of the library code files.

   • Save these files in your directory EC \include\.

3. Declare and define the following functions in your library : ecSysTick2.h

ecSysTick.h

void SysTick_init(uint32_t msec);
void delay_ms(uint32_t msec);
uint32_t SysTick_val(void);
void SysTick_reset (void);
void SysTick_enable(void);
void SysTick_disable (void)

2-2. Procedure

1. Create a new project under the directory

   \EC\lab\LAB_EXTI_SysTick

• The project name is “LAB_EXTI_SysTick”.

• Create a new source file named as “LAB_EXTI_SysTick.c”

You MUST write your name on the source file inside the comment section.

2. Include your updated library in \EC\include\ to your project.

• ecGPIO2.h, ecGPIO2.c

• ecRCC2.h, ecRCC2.c

• ecEXTI2.h, ecEXTI2.c

• ecSysTick2.h, ecSysTick2.c

1. First, check if every number, 0 to 9, can be displayed properly on the 7-segment.

2. Then, create a code to display the number counting from 0 to 9 and repeat at the rate of 1 second. (Use only one digit)

3. When the button is pressed, it should start from '0' again.

   Use EXTI for this button reset.

Configuration

Digital In for Button (B1)	Digital Out for FND-7-Segment
Digital In	Digital Out
PA4	PB7,PB6,PB5,PB4,PB3,PB2,PB1,PB0 ('a'~'h', respectively) PA10 ('LED4', respectively)
PULL-UP	Push-Pull, No Pull-up-Pull-down, Medium Speed

Circuit Diagram

You need to include the circuit diagram

image

Code

Your code goes here.

Explain your source code with necessary comments.

// YOUR MAIN CODE ONLY
// YOUR CODE

Results

Experiment images and results

Show experiment images /results

Add demo video link

Reference

Complete list of all references used (github, blog, paper, etc)

Troubleshooting

(Option) You can write a Troubleshooting section