# 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 {% embed url="" %} We are going to create a simple program that turns LED(LD2) on triggered by **External Interrupt** of user button(BT1)/ ### #### [attachInterrupt()](https://www.arduino.cc/reference/en/language/functions/external-interrupts/attachinterrupt/) ```c 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. ```c 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.
4. Click on **upload** button. 5. 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. {% embed url="" %} ### 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. {% embed url="" %} *** ## Problem 1: Counting numbers on 7-Segment using EXTI Button ### Creating EXTI library 1. [Download sample header files](https://github.com/ykkimhgu/EC-student/tree/main/include/lib-student): **`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** ```c 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** 3. 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). 4. 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](https://ykkim.gitbook.io/ec/firmware-programming/example-code#button-interrupt) ### 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](https://user-images.githubusercontent.com/38373000/192134563-72f68b29-4127-42ac-b064-2eda95a9a52a.png) ### 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 2. 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. ```c // YOUR MAIN CODE ONLY // YOUR CODE ``` ### Sample Code ```c #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](https://github.com/ykkimhgu/course-doc/blob/master/ec-course/lab/link/README.md) ## 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](https://github.com/ykkimhgu/EC-student/tree/main/include/lib-student): **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** ```c 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** 3. First, check if every number, 0 to 9, can be displayed properly on the 7-segment. 4. 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) 5. 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](https://user-images.githubusercontent.com/38373000/192134563-72f68b29-4127-42ac-b064-2eda95a9a52a.png) ### 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](https://github.com/ykkimhgu/course-doc/blob/master/ec-course/lab/link/README.md) ## Reference Complete list of all references used (github, blog, paper, etc) ``` ``` ## Troubleshooting (Option) You can write a Troubleshooting section