arduino | 易学教程

Arduino: printf/fprintf prints question mark instead of float

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问题 I have the following code for an Arduino sketch: #include <LiquidCrystal.h> LiquidCrystal lcd(12, 11, 5, 4, 3, 2); static FILE lcdout = {0} ; static int lcd_putchar(char ch, FILE* stream) { lcd.write(ch) ; return (0) ; } void setup() { lcd.begin(16, 2); fdev_setup_stream (&lcdout, lcd_putchar, NULL, _FDEV_SETUP_WRITE); } void loop() { stdout = &lcdout; printf("%.2f Volts", 2.0); } The problem comes at the last line of the code. This should print out "2.00 Volts" but instead, it prints "?

Apploader - upload Arduino sketches over BLE from iPad/iPhone - Start guide

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Basics Hardware Before we start check you have the following: 1. Arduino Uno , Arduino Mega 2560 or Arduino Nano board 2. HM-10 , HM-11(both preferred) or HC-8 BLE module First, set baud rate 115200 for your BLE module using AT-command for Uno or Mega2560 or 57600 for Nano board. For HM-10 you can use AT+BAUD? command to check current baud rate and AT+BAUD4 to set baud rate 115200 or AT+BAUD3 to set baud rate 57600. Consult HM-10 datasheet if necessary. You can use mega-to-hm10 sketch to use Mega as USB-to-TTL converter to send AT-commands: Second, wire the schematic: Arduino HM-10 pin 0 (RX

Serial communication between Arduino and Matlab is losing data

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问题 I am now trying to establish the serial communication between Arduino and Matlab. The script is very simple: Matlab send a number named as i to Arduino; Arduino receive this i , then send it back to Matlab; Repeat step 1&2 for 10 times, i.e., Matlab sends 1,2,...,10 to Arduino, then receive the 1,2,...,10 from Arduino. However, Matlab only get back 3,4,...,10, while the first i=1 and i=2 are lost (I have already made the inputbuffersize=200 now, still not right). Hereby is the code from

Convert serial.read() into a useable string using Arduino?

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问题 I'm using two Arduinos to sent plain text strings to each other using newsoftserial and an RF transceiver. Each string is perhaps 20-30 characters in length. How do I convert Serial.read() into a string so I can do if x == "testing statements" , etc.? 回答1: From Help with Serial.Read() getting string : char inData[20]; // Allocate some space for the string char inChar=-1; // Where to store the character read byte index = 0; // Index into array; where to store the character void setup() {

Mapping a numeric range onto another

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问题 Math was never my strong suit in school :( int input_start = 0; // The lowest number of the range input. int input_end = 254; // The lowest number of the range input. int output_start = 500; // The lowest number of the range output. int output_end = 5500; // The largest number of the range ouput. int input = 127; // Input value. int output = 0; How can I convert the input value to the corresponding output value of that range? For example, an input value of "0" would equal an output value of

Vectors in Arduino

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问题 I am making a vector of "waypoints" on the Arduino. Each waypoint is an object. The Arduino will obviously need to store multiple waypoints for waypoint navigation. But instead of storing these waypoints in a standard preprogrammed array, the user will need to be able to add, remove waypoints and move them around. Unfortunately the Arduino does not offer a vector type as a built-in library. I am currently contemplating two options: In Container for objects like C++ 'vector'? , someone posted

Vectors in Arduino

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Store value in variable after HTTPREAD

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问题 I am working with a GSM SIM900 and an Arduino Uno. I am using AT commands for the SIM900. I am successfully getting data from GET requests and showing on the serial monitor, but after the AT+HTTPREAD command I want to store data into a variable. How can I do this? I am getting a JSON Object from the web server and I want to get the Status property from that object and save it into a variable. #include <SoftwareSerial.h> SoftwareSerial gprsSerial(2,3); void setup() { gprsSerial.begin(9600);

arduino学习笔记十九--水位报警器

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介绍水位报警器，当水接触到2个金属头时候，触发报警。清单无源蜂鸣器一个一个LED 一个470欧姆电阻一个10K电阻 9根杜邦线实验板一片一个水杯（自备）原理图 1 接线，按照原理图接线 2准备一个被子，一瓶水做试验 3下载程序到 ARDUINO开发板 4 固定下2个检测触点。 5 慢慢倒水，当水同时接触到水时候，触发报警。代码： void setup() { pinMode(A5,OUTPUT); //让模拟口A5作为数字口输出 pinMode(A0, INPUT); } void loop() { int n=analogRead(A0); if (n>=100) { digitalWrite(A5, HIGH); pinMode(A2,OUTPUT); //蜂鸣器频响 0.5秒 tone(A2,800); delay(500); pinMode(A2,INPUT); digitalWrite(A5, LOW); delay(500); } } 来源： CSDN 作者：甜航一直在链接： https://blog.csdn.net/qq_37631068/article/details/103447615

arduino学习笔记二十--无源蜂鸣器+ARDUINO开发板播放音乐

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无源蜂鸣器+ARDUINO开发板播放音乐用到材料 1个无源蜂鸣器 2根杜邦线一片开发板原理图蜂鸣器长脚的为正，短脚为负极。在蜂鸣器的底下也有标价正负。接好线，选择喜欢的程序 1超级玛丽扬声器 2蜂鸣器唱歌小星星国际歌 3模拟防控警报的响声提供 3个测试程序，自己选择自己喜欢的下载玩玩。代码：超级玛丽 /* Play Super Mario theme song with Arduino and speaker circuit: * 8-ohm speaker on digital pin 8 created 4 June 2011 by naozhendang.com reference: http://arduino.cc/en/Tutorial/Tone */ #define NOTE_B0 31 #define NOTE_C1 33 #define NOTE_CS1 35 #define NOTE_D1 37 #define NOTE_DS1 39 #define NOTE_E1 41 #define NOTE_F1 44 #define NOTE_FS1 46 #define NOTE_G1 49 #define NOTE_GS1 52 #define NOTE_A1 55 #define NOTE_AS1 58 #define NOTE_B1 62