文章目录：
一、库文件的下载及导入
二、库文件源代码说明
三、库文件应用举例
一、库文件的下载及导入
有关arduino开源库的导入有两种方案：
1.第一种方案需要借助arduino.cc网站来进行查询下载，然后在Arduino软件中进行导入。
2.第二种方案则只需要使用较新版本的Arduino软件（2.2版本之后），在软件中可以直接搜索并导入开源库。
1.在Arduino.cc进行导入库
首先在网页地址框直接输入arduino.cc便可进入网站：
然后点击上方【DOCUMENTATION】选项：
在此页面点击左侧【Libraries】选项，便可进入官方收录的库文件页面：
选择要用的库文件的类目，这里以【display】为例：
然后点击具体的库文件，以【LiquidCrystal】为例：
进入库文件下载目录后，直接点击要用的版本号即可直接下载。
下载完成后如果不是压缩包，最好压缩成zip文件：
最后打开Arduino软件，选择【项目】-【导入库】-【添加.ZIP库】然后选择对应的zip文件即可导入成功。
2.使用Arduino软件导入库
上述方案较为复杂，所以建议使用较新版本的Arduino软件直接导入库：
在此版本的软件中直接点选左侧的“书籍”样式的图标（其表示为库文件），然后直接在搜索框查找要使用的库文件名，选择对应库文件及版本点击安装即可。
这种方案则最为简洁，当然有些时候要使用的库在软件中查询不到，此时就需要采用第一种方案进行导入。
2、库文件源代码说明
如上图所示，一般库文件中会有如上几个文件（会存在些许不同）。
1.示例程序的使用
example文件即为【示例】，这里面会有开源文件贡献者编写的几个示例程序，用于帮助学习者理解库的使用：
当然只要将库文件导入过Arduino中，也可以在Arduino软件中打开相应的示例程序：
2.【.h文件】及【.cpp】文件说明
在【src】文件夹中存在以下两个文件：
【.h】后缀我们称之为头文件，【.cpp】后缀我们称之为源文件
头文件通常包含类声明、函数原型、宏定义和全局变量声明等。它们的目的是提供一种方式来共享代码，并确保在多个源文件中使用一致的声明：
/*HCSR04 - Library for arduino, for HC-SR04 ultrasonic distance sensor.Created by Dirk Sarodnick, 2020.
*/#ifndef HCSR04_H
#define HCSR04_H#include "Arduino.h"#define HCSR04_INVALID_RESULT -1;
#define HCSR04_NO_TRIGGER -2;
#define HCSR04_NO_ECHO -3;class HCSR04Sensor {public:HCSR04Sensor();~HCSR04Sensor();typedef enum eUltraSonicUnlock {unlockSkip = 0,unlockMaybe = 1,unlockForced = 2} eUltraSonicUnlock_t;void begin(uint8_t triggerPin, uint8_t echoPin) { begin(triggerPin, new uint8_t[1]{ echoPin }, 1); }void begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount) { begin(triggerPin, echoPins, echoCount, 100000, eUltraSonicUnlock_t::unlockSkip); }void begin(uint8_t triggerPin, uint8_t echoPin, uint32_t timeout, eUltraSonicUnlock_t unlock) { begin(triggerPin, new uint8_t[1]{ echoPin }, 1, timeout, unlock); }void begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount, uint32_t timeout, eUltraSonicUnlock_t unlock) { begin(triggerPin, echoPins, echoCount, timeout, 10, 10, unlock); }void begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount, uint32_t timeout, uint16_t triggerTime, uint16_t triggerWait, eUltraSonicUnlock_t unlock);void end();long* measureMicroseconds() { measureMicroseconds(lastMicroseconds); return lastMicroseconds; }void measureMicroseconds(long* results);double* measureDistanceMm() { measureDistanceMm(defaultTemperature, lastDistances); return lastDistances; }void measureDistanceMm(double* results) { measureDistanceMm(defaultTemperature, results == NULL ? lastDistances : results); }double* measureDistanceMm(float temperature) { measureDistanceMm(temperature, lastDistances); return lastDistances; }void measureDistanceMm(float temperature, double* results);double* measureDistanceCm() { measureDistanceCm(defaultTemperature, lastDistances); return lastDistances; }void measureDistanceCm(double* results) { measureDistanceCm(defaultTemperature, results == NULL ? lastDistances : results); }double* measureDistanceCm(float temperature) { measureDistanceCm(temperature, lastDistances); return lastDistances; }void measureDistanceCm(float temperature, double* results);double* measureDistanceIn() { measureDistanceIn(defaultTemperature, lastDistances); return lastDistances; }void measureDistanceIn(double* results) { measureDistanceIn(defaultTemperature, results == NULL ? lastDistances : results); }double* measureDistanceIn(float temperature) { measureDistanceIn(temperature, lastDistances); return lastDistances; }void measureDistanceIn(float temperature, double* results);static void triggerInterrupt0(void);static void triggerInterrupt1(void);static void triggerInterrupt2(void);static void triggerInterrupt3(void);static void triggerInterrupt4(void);static void triggerInterrupt5(void);static void triggerInterrupt6(void);static void triggerInterrupt7(void);static void triggerInterrupt8(void);static void triggerInterrupt9(void);static void echoInterrupt0(void);static void echoInterrupt1(void);static void echoInterrupt2(void);static void echoInterrupt3(void);static void echoInterrupt4(void);static void echoInterrupt5(void);static void echoInterrupt6(void);static void echoInterrupt7(void);static void echoInterrupt8(void);static void echoInterrupt9(void);private:float defaultTemperature = 19.307;long* lastMicroseconds;double* lastDistances;uint32_t timeout;uint16_t triggerTime = 10; // HC-SR04 needs at least 10�s trigger. Others may need longer trigger pulses.uint16_t triggerWait = 10; // HC-SR04 sends its signal about 200�s. We only wait a small amount to reduce interference, but to not miss anything on slower clock speeds.volatile uint8_t triggerPin;volatile unsigned long* volatile triggerTimes;uint8_t echoCount;volatile int16_t* volatile echoStages;volatile int16_t* volatile echoInts;volatile int16_t* volatile echoPorts;volatile unsigned long* volatile echoTimes;void triggerInterrupt(uint8_t);void echoInterrupt(uint8_t);void unlockSensors(eUltraSonicUnlock_t, uint8_t*);
};extern HCSR04Sensor HCSR04;#endif // HCSR04_H
源文件包含了实现代码，即函数和方法的定义。它们通常包含与头文件对应的实现：
/*HCSR04 - Library for arduino, for HC-SR04 ultrasonic distance sensor.Created by Dirk Sarodnick, 2020.
*/#include "Arduino.h"
#include "HCSR04.h"HCSR04Sensor::HCSR04Sensor() {}
HCSR04Sensor::~HCSR04Sensor() { this->end(); }void HCSR04Sensor::begin(uint8_t triggerPin, uint8_t* echoPins, uint8_t echoCount, uint32_t timeout, uint16_t triggerTime, uint16_t triggerWait, eUltraSonicUnlock_t unlock) {if (this->echoCount != echoCount) this->end();this->triggerPin = triggerPin;pinMode(triggerPin, OUTPUT);this->timeout = timeout;this->triggerTime = triggerTime;this->triggerWait = triggerWait;this->echoCount = echoCount;if (this->lastMicroseconds == NULL) this->lastMicroseconds = new long[echoCount];if (this->lastDistances == NULL) this->lastDistances = new double[echoCount];if (this->triggerTimes == NULL) this->triggerTimes = new unsigned long[echoCount];if (this->echoTimes == NULL) this->echoTimes = new unsigned long[echoCount];if (this->echoStages == NULL) this->echoStages = new int16_t[echoCount];if (this->echoInts == NULL) this->echoInts = new int16_t[echoCount];if (this->echoPorts == NULL) this->echoPorts = new int16_t[echoCount];for (uint8_t i = 0; i < this->echoCount; i++) {this->triggerTimes[i] = 0;this->echoTimes[i] = 0;int16_t interrupt = digitalPinToInterrupt(echoPins[i]);if (interrupt == NOT_AN_INTERRUPT) {this->echoStages[i] = -1;this->echoInts[i] = -1;this->echoPorts[i] = echoPins[i];} else {this->echoStages[i] = 0;this->echoInts[i] = interrupt;this->echoPorts[i] = -1;}pinMode(echoPins[i], INPUT);}// Unlock sensors that are possibly in a locked state, if this feature is enabled.this->unlockSensors(unlock, echoPins);
}void HCSR04Sensor::end() {if (this->lastMicroseconds != NULL) delete []this->lastMicroseconds;if (this->lastDistances != NULL) delete []this->lastDistances;if (this->triggerTimes != NULL) delete []this->triggerTimes;if (this->echoTimes != NULL) delete []this->echoTimes;if (this->echoPorts != NULL) delete []this->echoPorts;if (this->echoInts != NULL) delete []this->echoInts;if (this->echoStages != NULL) delete []this->echoStages;this->lastMicroseconds = NULL;this->lastDistances = NULL;this->triggerTimes = NULL;this->echoTimes = NULL;this->echoPorts = NULL;this->echoInts = NULL;this->echoStages = NULL;
}void HCSR04Sensor::measureMicroseconds(long* results) {if (results == NULL) results = this->lastMicroseconds;bool finished = true;bool waiting = true;unsigned long startMicros = micros();unsigned long currentMicros = 0;unsigned long elapsedMicros = 0;// Make sure that trigger pin is LOW.digitalWrite(triggerPin, LOW);delayMicroseconds(4);// Hold trigger HIGH for 10 microseconds (default), which signals the sensor to measure distance.digitalWrite(triggerPin, HIGH);delayMicroseconds(this->triggerTime);// Set trigger LOW again and wait to give the sensor time for sending the signal without interferencedigitalWrite(triggerPin, LOW);delayMicroseconds(this->triggerWait);// Attach interrupts to echo pins for the starting pointfor (uint8_t i = 0; i < this->echoCount; i++) {if (this->echoInts[i] >= 0 && this->echoStages[i] == 0) {this->echoStages[i] = 1;switch (i) {case 0: attachInterrupt(this->echoInts[i], &triggerInterrupt0, RISING); break;case 1: attachInterrupt(this->echoInts[i], &triggerInterrupt1, RISING); break;case 2: attachInterrupt(this->echoInts[i], &triggerInterrupt2, RISING); break;case 3: attachInterrupt(this->echoInts[i], &triggerInterrupt3, RISING); break;case 4: attachInterrupt(this->echoInts[i], &triggerInterrupt4, RISING); break;case 5: attachInterrupt(this->echoInts[i], &triggerInterrupt5, RISING); break;case 6: attachInterrupt(this->echoInts[i], &triggerInterrupt6, RISING); break;case 7: attachInterrupt(this->echoInts[i], &triggerInterrupt7, RISING); break;case 8: attachInterrupt(this->echoInts[i], &triggerInterrupt8, RISING); break;case 9: attachInterrupt(this->echoInts[i], &triggerInterrupt9, RISING); break;}}}// Wait until all echos are returned or timed out.while(true) {delayMicroseconds(1);finished = true;waiting = true;currentMicros = micros();elapsedMicros = currentMicros - startMicros;for (uint8_t i = 0; i < this->echoCount; i++) {waiting &= elapsedMicros < this->timeout || (this->triggerTimes[i] > 0 && this->echoTimes[i] == 0 && (currentMicros - this->triggerTimes[i]) < this->timeout);if (this->echoPorts[i] >= 0 && this->triggerTimes[i] == 0) {if (digitalRead(this->echoPorts[i]) == HIGH) this->triggerTimes[i] = micros();}if (this->triggerTimes[i] > 0 || !waiting) {if (this->echoInts[i] >= 0 && (this->echoStages[i] == 1 || !waiting)) {if (this->echoStages[i] == 1) this->echoStages[i] = 2;detachInterrupt(this->echoInts[i]);}} else finished &= false;if (this->echoInts[i] >= 0 && this->triggerTimes[i] > 0 && this->echoStages[i] == 2 && waiting) {this->echoStages[i] = 3;switch (i) {case 0: attachInterrupt(this->echoInts[i], &echoInterrupt0, FALLING); break;case 1: attachInterrupt(this->echoInts[i], &echoInterrupt1, FALLING); break;case 2: attachInterrupt(this->echoInts[i], &echoInterrupt2, FALLING); break;case 3: attachInterrupt(this->echoInts[i], &echoInterrupt3, FALLING); break;case 4: attachInterrupt(this->echoInts[i], &echoInterrupt4, FALLING); break;case 5: attachInterrupt(this->echoInts[i], &echoInterrupt5, FALLING); break;case 6: attachInterrupt(this->echoInts[i], &echoInterrupt6, FALLING); break;case 7: attachInterrupt(this->echoInts[i], &echoInterrupt7, FALLING); break;case 8: attachInterrupt(this->echoInts[i], &echoInterrupt8, FALLING); break;case 9: attachInterrupt(this->echoInts[i], &echoInterrupt9, FALLING); break;}}if (this->echoPorts[i] >= 0 && this->triggerTimes[i] > 0 && this->echoTimes[i] == 0) {if (digitalRead(this->echoPorts[i]) == LOW) this->echoTimes[i] = micros();}if ((this->triggerTimes[i] > 0 && this->echoTimes[i] > 0) || !waiting) {if (this->echoInts[i] >= 0 && (this->echoStages[i] == 3 || !waiting)) {if (this->echoStages[i] == 3) this->echoStages[i] = 4;detachInterrupt(this->echoInts[i]);}} else finished &= false;}if (!waiting || finished) break;}// Determine the durations of each sensor.for (uint8_t i = 0; i < this->echoCount; i++) {if (this->echoInts[i] >= 0) this->echoStages[i] = 0;if (this->triggerTimes[i] > 0 && this->echoTimes[i] > 0) {long resultTime = this->echoTimes[i] - this->triggerTimes[i];results[i] = resultTime > 0 ? resultTime : HCSR04_INVALID_RESULT;} else if (this->triggerTimes[i] > 0) {results[i] = HCSR04_NO_ECHO;} else {results[i] = HCSR04_NO_TRIGGER;}this->triggerTimes[i] = 0;this->echoTimes[i] = 0;}
}void HCSR04Sensor::measureDistanceMm(float temperature, double* results) {if (results == NULL) results = this->lastDistances;double speedOfSoundInMmPerMs = (331.3 + 0.606 * temperature) / 1000; // Cair ≈ (331.3 + 0.606 ⋅ ϑ) m/slong* times = measureMicroseconds();// Calculate the distance in mm for each result.for (uint8_t i = 0; i < this->echoCount; i++) {double distanceMm = times[i] / 2.0 * speedOfSoundInMmPerMs;if (distanceMm < 10 || distanceMm > 4000) {results[i] = HCSR04_INVALID_RESULT;} else {results[i] = distanceMm;}}
}void HCSR04Sensor::measureDistanceCm(float temperature, double* results) {if (results == NULL) results = this->lastDistances;double speedOfSoundInCmPerMs = (331.3 + 0.606 * temperature) / 1000 / 10; // Cair ≈ (331.3 + 0.606 ⋅ ϑ) m/slong* times = measureMicroseconds();// Calculate the distance in cm for each result.for (uint8_t i = 0; i < this->echoCount; i++) {double distanceCm = times[i] / 2.0 * speedOfSoundInCmPerMs;if (distanceCm < 1 || distanceCm > 400) {results[i] = HCSR04_INVALID_RESULT;} else {results[i] = distanceCm;}}
}void HCSR04Sensor::measureDistanceIn(float temperature, double* results) {if (results == NULL) results = this->lastDistances;double speedOfSoundInCmPerMs = (331.3 + 0.606 * temperature) * 39.37007874 / 1000 / 1000; // Cair ≈ (331.3 + 0.606 ⋅ ϑ) m/slong* times = measureMicroseconds();// Calculate the distance in cm for each result.for (uint8_t i = 0; i < this->echoCount; i++) {double distanceIn = times[i] / 2.0 * speedOfSoundInCmPerMs;if (distanceIn < 1 || distanceIn > 157.4804) {results[i] = HCSR04_INVALID_RESULT;}else {results[i] = distanceIn;}}
}void HCSR04Sensor::unlockSensors(eUltraSonicUnlock_t unlock, uint8_t* echoPins) {if (unlock == eUltraSonicUnlock_t::unlockSkip) return;bool hasLocked = false;// Check if any sensor is in a locked state and unlock it if necessary.for (uint8_t i = 0; echoPins[i] != 0; i++) {if (unlock == eUltraSonicUnlock_t::unlockMaybe && digitalRead(echoPins[i]) == LOW) continue;pinMode(echoPins[i], OUTPUT);digitalWrite(echoPins[i], LOW);hasLocked = true;}if (hasLocked) delay(100);// Revert the pinMode after potential unlocking.for (uint8_t i = 0; echoPins[i] != 0; i++) {pinMode(echoPins[i], INPUT);}if (hasLocked) delay(100);
}void HCSR04Sensor::triggerInterrupt(uint8_t index) {if (this->triggerTimes[index] == 0) this->triggerTimes[index] = micros();
}void HCSR04Sensor::echoInterrupt(uint8_t index) {if (this->triggerTimes[index] > 0 && this->echoTimes[index] == 0) this->echoTimes[index] = micros();
}void HCSR04Sensor::triggerInterrupt0() { HCSR04.triggerInterrupt(0); }
void HCSR04Sensor::triggerInterrupt1() { HCSR04.triggerInterrupt(1); }
void HCSR04Sensor::triggerInterrupt2() { HCSR04.triggerInterrupt(2); }
void HCSR04Sensor::triggerInterrupt3() { HCSR04.triggerInterrupt(3); }
void HCSR04Sensor::triggerInterrupt4() { HCSR04.triggerInterrupt(4); }
void HCSR04Sensor::triggerInterrupt5() { HCSR04.triggerInterrupt(5); }
void HCSR04Sensor::triggerInterrupt6() { HCSR04.triggerInterrupt(6); }
void HCSR04Sensor::triggerInterrupt7() { HCSR04.triggerInterrupt(7); }
void HCSR04Sensor::triggerInterrupt8() { HCSR04.triggerInterrupt(8); }
void HCSR04Sensor::triggerInterrupt9() { HCSR04.triggerInterrupt(9); }void HCSR04Sensor::echoInterrupt0() { HCSR04.echoInterrupt(0); }
void HCSR04Sensor::echoInterrupt1() { HCSR04.echoInterrupt(1); }
void HCSR04Sensor::echoInterrupt2() { HCSR04.echoInterrupt(2); }
void HCSR04Sensor::echoInterrupt3() { HCSR04.echoInterrupt(3); }
void HCSR04Sensor::echoInterrupt4() { HCSR04.echoInterrupt(4); }
void HCSR04Sensor::echoInterrupt5() { HCSR04.echoInterrupt(5); }
void HCSR04Sensor::echoInterrupt6() { HCSR04.echoInterrupt(6); }
void HCSR04Sensor::echoInterrupt7() { HCSR04.echoInterrupt(7); }
void HCSR04Sensor::echoInterrupt8() { HCSR04.echoInterrupt(8); }
void HCSR04Sensor::echoInterrupt9() { HCSR04.echoInterrupt(9); }HCSR04Sensor HCSR04;
三、库文件应用举例
下文以超声波传感器的库HCSR04来进行举例（仅说明代码用法，不作实物接线）
在导入HCSR04库之后，可打开库文件中的实例：
#include <HCSR04.h>HCSR04 hc(5, 6); //initialisation class HCSR04 (trig pin , echo pin)//初始化超声波传感器，即表明接口号。void setup()
{Serial.begin(9600); //串口初始化
}void loop()
{Serial.println(hc.dist()); // return curent distance in serial// hc.dist()会返回超声波传感器检测的距离数据delay(60); // 延时60毫秒
}
具体实例可参考文章——Arduino项目式编程教学第四章——超声波测距
如果想要了解此库文件下的方法，则可以在Arduino软件中，按住【Alt / cmd】键，然后使用鼠标点击对应的库文件名，即可打开其头文件：
在头文件中，可以阅读文件贡献者做出的注释来了解此库文件中可供使用的方法。