04 - String Class and Digital Input.pdf

String Class와 디지털 입력 부산대학교 정보∙의생명공학대학 정보컴퓨터공학부 String Class ❖ Class for String Manipulation ❖ Example Code ▪ Reference : ▪ String stringOne = "Hello String";...

String Class와 디지털 입력 부산대학교 정보∙의생명공학대학 정보컴퓨터공학부 String Class ❖ Class for String Manipulation ❖ Example Code ▪ Reference : ▪ String stringOne = "Hello String"; //using a constant String https://www.arduino.cc/reference/en/lang uage/variables/data-types/stringobject/ ▪ String stringOne = String('a'); //converting a constant char into a ▪ C++의 문자열 처리를 위한 std::string String Class 등과 유사 ▪ String stringTwo = String("This is a string"); ▪ Serial Class와 같이 별도의 Header file //converting a constant string into a include 없이 사용할 수 있는 기본 Class String object ❖ String(val,base, decimalPlaces) ▪ String stringOne = String(stringTwo + " with more"); // concatenating two strings ▪ Constructs an instance of the String class ▪ String stringOne = String(13); ▪ 문자, 문자열, 숫자 등으로부터 String 객 // using a constant integer 체 생성 가능 ▪ String stringOne = String(analogRead(0), DEC); ▪ val : a variable to format as a String - // using an int and a base Allowed data types: string, char, byte, int, long, unsigned int, unsigned long, float, ▪ String stringOne = String(45, HEX); double // using an int and a base (hexadecimal) ▪ String stringOne = String(255, BIN); ▪ base (optional): the base in which to // using an int and a base (binary) format an integral value ▪ String stringOne = String(millis(), ▪ decimalPlaces (optional): (only if val is DEC); float or double): the desired decimal // using a long and a base places ▪ String stringOne = String(5.698, 3); // using a float and the decimal places 2 String Class : Operators ❖ Supported Operators ❖ + : concatenation ▪ [] (element access) ▪ String 객체와 다른 타입의 데이터 결합 으로 새로운 String 객체 생성 ▪ + (concatenation) ▪ String(“abc”) + 123; ▪ += (append) // String 객체 + 정수 ▪ == (comparison) ▪ cf) “ ” 표시되는 문자열은 String 클래 ▪ > (greater than) 스 객체가 아닌 문자 배열로 처리 ▪ >= (greater than or equal to) ▪ “abc” + 123; // 문자열 배열 + 정수 () ▪ < (less than) ▪ 0) { // sorts an array in ascending order String temp = str[i]; str[i] = str[j]; Explain the sorting precedure of the following array, str[j] = temp; {"red", "orange", "yellow", "green", "blue", "indigo", "violet"}? } } How can you sort an array in decending order, not } ascending? // prints an sorted array of strings for (int i = 0; i < 5; i++) { Serial.println(String(i) + " : " + str[i]); } while (true); } 8 Lab.4-1 ③ Receiving a String Input from Serial Sketch - Lab 4-1-3a ❖ Receiving a string input in void setup() { Serial.begin(9600); // Open the serial port Arduino? } ▪ Input functions of Arduino Serial Class void loop() { int state = 1, len = 0; read(), readBytes(), readBytesUntil(), char buffer; parseInt(), parseFloat(), peek(), … while (true) { ▪ No function for string input in Arduino. if (state == 1) { There is no function receiving a string Serial.print("Enter a String --> "); input like gets() of standard C. state = 2; } – Arduino doesn’t support while (Serial.available()) { functions of standard C, such as printf(), char data = Serial.read(); scanf(), puts(), and gets() if (data == '\n') { – Usually, Arduino is used for hardware // reads input until newline ‘\n’ control. So, human interaction is rare. buffer[len] = '\0'; ▪ Receiving a string input using read() or String in_str = buffer; Serial.println(in_str + " [" + readBytesUntil() in_str.length()+"]"); state = 1; len = 0; break; } buffer[len++] = data; } } } 9 Lab.4-1 ③ Receiving a String Input from Serial Sketch - Lab 4-1-3b void setup() { Select ‘New Line’(새줄) to send new line Serial.begin(9600); // Open the serial port character for every Enter in Serial Monitor } as you can see the figure below. void loop() { int state = 1; char buffer; while (true) { if (state == 1) { Serial.print("Enter a String --> "); state = 2; } while (Serial.available()) { int len = Serial.readBytesUntil('\n', buffer, 127); if (len > 0) { buffer[len] = '\0'; String in_str = String(buffer); Serial.println(in_str + " [" + in_str.length()+"]"); state = 1; break; } } } } 10 Lab.4-1 ④ Check the Result 1. Show your four Sketch code 2. Show the execution of Lab 4-1-3b Sketch on a Serial Monitor 3. Answer the TA’s questions and insert the score result to PLMS LAB 4-1 11 HW.4-1 Homework ❖ Write a Sketch code that ❖ Submission receives 5 words input, then 1. Insert your Sketch code to PLMS HW print them out in ascending 4-1. order as you can see in the 2. Capture a screenshot of the Serial following figure. Monitor and upload it to also PLMS. 12 DIGITAL INPUT - BUTTON 13 Button Connecting – Basic Circuit ❖ 버튼 on(push) : 1 ( Vcc) ❖ 버튼 Off : 0 ? ❖ Floating Input Problem ▪ Digital 입력 핀에 아무런 회로가 연결 되지 않은 상황 ▪ 주변 핀의 상태나 정전기 등에 의해 임 의의 값이 입력될 수 있음 ▪ 버튼을 사용할 때는 회로가 오픈 되는 경우를 피해야 한다 ▪ 풀다운 저항의 사용 Button Connecting – Pull-down Resistor ❖ Pull-down ❖ Button on(push) : 1 (Vcc) ❖ Button off : 0 (Gnd) Button Connecting – Pull-up Resistor ❖ Pull-up ❖ 버튼 on(push) : 0 (Gnd) ❖ 버튼 off : 1 ( Vcc) Button Connecting PUll-up/Pull-down Unpressed Pressed resistor Floating Not used 1 (neither 1 nor 0) Pull-down resistor 0 1 Pull-up resistor 1 0 Lab.4-2 Pull-up / Pull-down Buttons ❖ Experiment Sequence ① Constructing a Circuit using Pull-up / Pull-down buttons ② Printing Out the Button State (Sketch 6-1, Textbook pp. 103) ③ Constructing a Circuit using the Button Connected to an Internal Pull-up Resistor ④ Printing Out the State of the Button connected to an Internal Pull-up resistor (Sketch 6-2, Textbook pp.106) ⑤ Constructing a Circuit using LEDs and Buttons ⑥ Indicating a Button State using LEDs (Sketch 6-3, Textbook pp. 107~108) ⑦ Turning on and off LED using Buttons (Sketch 6-4, Textbook pp. 109) ⑧ Counting the Number of Button Presses (Sketch 6-5, Textbook pp. 111~112) ⑨ Check the Result 18  ① Constructing a Circuit using Pull-up / Pull-down Lab.4-2 Buttons Pull-down resistor Pull-up resistor Lab.4-2 ② Printing Out the Button State Sketch 6-1, Textbook pp. 103 int buttons[] = {14, 15, 16, 17}; // Pins connected to buttons void setup() { Serial.begin(9600); // Open the serial port at 9600 bps for (int i = 0; i < 4; i++) { // Sets the Digital Pins as input pinMode(buttons[i], INPUT); } } void loop() { for (int i = 0; i < 4; i++) { Serial.print(digitalRead(buttons[i])); // Prints out the button Serial.print(" "); // state } Serial.println(); // New line delay(1000); } When pull-up resistors are used, the result is not intuitive. Functions for Data Input Arduino has internal pull-up resistors inside microcontroller  ① Lab.4-2 ③ Constructing a Circuit using a Button Connected to an Internal Pull-up Resistors Internal pull-up resistor If an internal pull-up resistor is not used, a button should be connected to VCC ❖ In Arduino, each pin has an internal pull-up resistor Lab.4-2 ④ Printing Out the State of the Button Connected to an Internal Pull-up resistor Sketch 6-2, Textbook pp. 106 int button = 21; // Pin connected to a button void setup() { Serial.begin(9600); // Open the serial port at 9600 bps pinMode(button, INPUT_PULLUP); // Sets the Digital Pins as input } void loop() { Serial.println(digitalRead(button)); // Prints out the button state delay(1000); } 23 Lab.4-2 ⑤ Constucting a Circuit using LEDs and Buttons Using pull-down resistor Using pull-up resistor Lab.4-2 ⑥ Indicating a Button State using LEDs Sketch 6-3, Textbook pp. 107~108 int pins_LED[] = {2, 3}; // Pins connected to LEDs // Pins connected to buttons (15 : pull-down resistor, 16 : pull-up resistor) int pins_button[] = {15, 16}; void setup() { Serial.begin(9600); // Open the serial port at 9600 bps for (int i = 0; i < 2; i++) { pinMode(pins_button[i], INPUT); // Sets the Digital Pins as input pinMode(pins_LED[i], OUTPUT); // Sets the Digital Pins as output } } void loop() { for (int i = 0; i < 2; i++) { boolean state = digitalRead(pins_button[i]); // Reads the button state digitalWrite(pins_LED[i], state); // LED output Serial.print(state); Serial.print(" "); } Serial.println(); delay(1000); } 25 Lab.4-2 ⑦ Turning on and off LED using Buttons ❖ If a pull-up resistor is used, the state of unpressed button is HIGH, not intuitive ❖ Creating an array of the LED patterns for button state boolean on_off_pattern = { {false, true}, // Using a pull-down resistor {true, false} // Using a pull-up resistor }; ❖ Controlling a LED using pre-defined LED pattern values for button state boolean state = digitalRead(pins_button[i]); digitalWrite(pins_LED[i], on_off_pattern[i][state]); Lab.4-2 ⑦ Turning on and off LED using Buttons int pins_LED[] = {2, 3}; // Pins connected to LED Sketch 6-4, Textbook pp. 109 // Pins connected to buttons (15 : Pull-down resistor, 16 : Pull-up resistor) int pins_button[] = {15, 16}; boolean on_off_pattern = { // LED lighting patterns {false, true}, // Using pull-down resistor {true, false} // Using pull-up resistor }; void setup() { Serial.begin(9600); // Open the serial port at 9600 bps for (int i = 0; i < 2; i++) { pinMode(pins_button[i], INPUT); // Sets the Digital Pins as input pinMode(pins_LED[i], OUTPUT); // Sets the Digital Pins as output } } void loop() { for (int i = 0; i < 2; i++) { boolean state = digitalRead(pins_button[i]); // Reads the button state digitalWrite(pins_LED[i], on_off_pattern[i][state]); // LED output Serial.print(on_off_pattern[i][state]); Serial.print(" "); } Serial.println(); delay(1000); } Lab.4-2 ⑧ Counting the Number of Button Presses ❖ If a button is pushed, the button counter increases. If a button is pushed and held continuously, the button counter will keep increasing ❖ Increase the button counter only if previous state of the button (state_previous) is unpressed state and current state of the button (state_current)is pressed state ❖ Bouncing / Chattering: A button state changes repeatedly between ON and OFF due to mechanical vibration ▪ Debouncing : removing a chattering Lab.4-2 ⑧ Counting the Number of Button Presses Sketch 6-5, Textbook pp. 111~112 int pin_button = 15; // Pins connected to buttons boolean state_previous = false; // Previous state of a button boolean state_current; // Current state of a button int count = 0; // The number of Button pressed void setup() { Serial.begin(9600); // Open the serial port at 9600 bps pinMode(pin_button, INPUT); //} Sets the Digital Pins as input void loop() { state_current = digitalRead(pin_button); // Reads the button state if (state_current) { // Button is pressed if (state_previous == false) { // Compares to previous state count++; // Increases the button counter state_previous = true; Serial.println(count); } // delay(50); // Debouncing } else { state_previous = false; } } Lab.4-2 ⑨ Check the Result 1. Show 5 Sketch code you have written 2. Show an execution of the Lab 6-4 Sketch 3. Answer the TA’s questions and insert the score result to PLMS LAB 4-2 30 HW.4-2 Homework ❖ Exercise 6.3 ❖ Submission ▪ Connect 4 LEDs to digital pin 2 ~5, and 1. Insert your Sketch code to PLMS HW 4-2 connect a button to digital pin 14 using pull-down resistor. 2. Submit a link to the video recording the result of your work. ▪ LEDs should be blinked with 0.5 second interval in the forward direction, 1->2->3- >4->1.... ▪ If the button is pressed, LED bliking sequence should be inverted. Patte Digital Pin ▪ In other words, if the button is pressed, rn 2번 3번 4번 5번 LED bliking sequence is changed into 1 backward direction, 4->3->2->1->4... 2 Notice that in the beginning, the LED 3 bliking sequence is the forward direction. 4 맺는말 ❖ 데이터 핀을 통한 디지털 데이터 입력 ▪ digitalRead 함수로 비트 단위 입력이 가능하지만 ▪ pinMode 함수로 입력으로 사용할 것임을 먼저 지정해야 함 ❖ 버튼이 눌러지지 않은 경우 회로가 오픈 상태에 있어 핀으로의 입력이 결 정되지 않는 플로팅 상태 발생 ▪ 풀업 저항으로 버튼이 눌러지지 않은 경우 HIGH가 입력되도록 설정 ▪ 풀다운 저항으로 버튼이 눌러지지 않은 경우 LOW가 입력되도록 설정 ▪ ATmega2560 내부에는 풀업 저항이 포함되어 있으므로 별도의 저항 연결 없이 사용 가 능