原创 指纹传感器与Arduino的接口（附代码）

指纹传感器是应用广泛的感知元件，本项目以R502/R503电容式指纹传感器为例，演示如何通过Arduino开发板录入和检测指纹。项目BOM清单如下：
Arduino开发板 1
指纹传感器R503 1
杜邦线    20
面包板          1

与光学指纹传感器的创建指纹图像不同，电容式产品采用微电容电路组成的阵列来收集数据。当手指按压到采集面上时，手指的脊和谷在表皮和芯片之间产生不同的微小电容,芯片通过测量空间中的不同的电磁场得到完整的指纹信息，并通过运放和ADC进行处理。例如，R502/R503就能识别干、湿指纹，而前者更轻巧。

以R503为例，该传感器内嵌指纹识别算法和协议，具有指纹采集、比对、搜索和模板存储等功能。R503图像大小192*192，分辨率达508 DPI，可存储200个指纹，FRR≤0.01%，FAR≤0.00001%，支持Arduino、Android、Windows、Linux等。

R503支持低功耗手指检测，工作电压3.3V，采集电流不超过18mA，平均待机电流仅2uA。R503通过RS232 UART接口，通讯速率达57600bps，用于电脑外设、指纹门锁、指纹挂锁、保险柜等。

把R502/R503与Arduino连接，电电路很简单。

.
把R502/R503的VCC、GND、Tx (黄线)、Rx (绿线)四个引脚分别连接到Arduino开发板的3.3V、GND、D2、D3引脚.，蓝色的中断线不用连接，白色引线接到3.3V引脚上。

Github仓库有Adafruit编写的关于R502/R503指纹传感器的Arduino库文件。指纹录入和阅读是分开的，录入代码保存在EEPROM存储器中，阅读代码从EEPROM中读取数据并与扫描到的指纹数据校验匹配。
指纹录入代码如下：

#include

#if (defined(__AVR__) || defined(ESP8266)) && !defined(__AVR_ATmega2560__)
// For UNO and others without hardware serial, we must use software serial...
// pin #2 is IN from sensor (GREEN wire)
// pin #3 is OUT from arduino(WHITE wire)
// Set up the serial port to use softwareserial..
SoftwareSerial mySerial(2, 3);

#else
// On Leonardo/M0/etc, others with hardware serial, use hardware serial!
// #0 is green wire, #1 is white
#define mySerial Serial1

#endif

Adafruit_Fingerprint finger = Adafruit_Fingerprint(&mySerial);

uint8_t id;

void setup()
{
Serial.begin(9600);
while (!Serial);// For Yun/Leo/Micro/Zero/...
delay(100);
Serial.println("\n\nAdafruit Fingerprint sensor enrollment");

// set the data rate for the sensor serial port
finger.begin(57600);

if (finger.verifyPassword()) {
Serial.println("Found fingerprint sensor!");
} else {
Serial.println("Did not find fingerprint sensor : (");
while (1) { delay(1); }
}

Serial.println(F("Reading sensor parameters"));
finger.getParameters();
Serial.print(F("Status: 0x")); Serial.println(finger.status_reg, HEX);
Serial.print(F("Sys ID: 0x")); Serial.println(finger.system_id, HEX);
Serial.print(F("Capacity: ")); Serial.println(finger.capacity);
Serial.print(F("Security level: ")); Serial.println(finger.security_level);
Serial.print(F("Device address: ")); Serial.println(finger.device_addr, HEX);
Serial.print(F("Packet len: ")); Serial.println(finger.packet_len);
Serial.print(F("Baud rate: ")); Serial.println(finger.baud_rate);
}

uint8_t readnumber(void) {
uint8_t num = 0;

while (num == 0) {
while (! Serial.available());
num = Serial.parseInt();
}
return num;
}

void loop() // run over and over again
{
Serial.println("Ready to enroll a fingerprint!");
Serial.println("Please type in the ID # (from 1 to 127) you want to save this finger as...");
id = readnumber();
if (id == 0) {// ID #0 not allowed, try again!
return;
}
Serial.print("Enrolling ID #");
Serial.println(id);

while (!getFingerprintEnroll() );
}

uint8_t getFingerprintEnroll() {

int p = -1;
Serial.print("Waiting for valid finger to enroll as #"); Serial.println(id);
while (p != FINGERPRINT_OK) {
p = finger.getImage();
switch (p) {
case FINGERPRINT_OK:
Serial.println("Image taken");
break;
case FINGERPRINT_NOFINGER:
Serial.println(".");
break;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
break;
case FINGERPRINT_IMAGEFAIL:
Serial.println("Imaging error");
break;
default:
Serial.println("Unknown error");
break;
}
}

// OK success!

p = finger.image2Tz(1);
switch (p) {
case FINGERPRINT_OK:
Serial.println("Image converted");
break;
case FINGERPRINT_IMAGEMESS:
Serial.println("Image too messy");
return p;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
return p;
case FINGERPRINT_FEATUREFAIL:
Serial.println("Could not find fingerprint features");
return p;
case FINGERPRINT_INVALIDIMAGE:
Serial.println("Could not find fingerprint features");
return p;
default:
Serial.println("Unknown error");
return p;
}

Serial.println("Remove finger");
delay(2000);
p = 0;
while (p != FINGERPRINT_NOFINGER) {
p = finger.getImage();
}
Serial.print("ID "); Serial.println(id);
p = -1;
Serial.println("Place same finger again");
while (p != FINGERPRINT_OK) {
p = finger.getImage();
switch (p) {
case FINGERPRINT_OK:
Serial.println("Image taken");
break;
case FINGERPRINT_NOFINGER:
Serial.print(".");
break;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
break;
case FINGERPRINT_IMAGEFAIL:
Serial.println("Imaging error");
break;
default:
Serial.println("Unknown error");
break;
}
}

// OK success!

p = finger.image2Tz(2);
switch (p) {
case FINGERPRINT_OK:
Serial.println("Image converted");
break;
case FINGERPRINT_IMAGEMESS:
Serial.println("Image too messy");
return p;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
return p;
case FINGERPRINT_FEATUREFAIL:
Serial.println("Could not find fingerprint features");
return p;
case FINGERPRINT_INVALIDIMAGE:
Serial.println("Could not find fingerprint features");
return p;
default:
Serial.println("Unknown error");
return p;
}

// OK converted!
Serial.print("Creating model for #");Serial.println(id);

p = finger.createModel();
if (p == FINGERPRINT_OK) {
Serial.println("Prints matched!");
} else if (p == FINGERPRINT_PACKETRECIEVEERR) {
Serial.println("Communication error");
return p;
} else if (p == FINGERPRINT_ENROLLMISMATCH) {
Serial.println("Fingerprints did not match");
return p;
} else {
Serial.println("Unknown error");
return p;
}

Serial.print("ID "); Serial.println(id);
p = finger.storeModel(id);
if (p == FINGERPRINT_OK) {
Serial.println("Stored!");
} else if (p == FINGERPRINT_PACKETRECIEVEERR) {
Serial.println("Communication error");
return p;
} else if (p == FINGERPRINT_BADLOCATION) {
Serial.println("Could not store in that location");
return p;
} else if (p == FINGERPRINT_FLASHERR) {
Serial.println("Error writing to flash");
return p;
} else {
Serial.println("Unknown error");
return p;
}

return true;
}

上传代码后，打开Serial Monitor，监视器将询问位于1-127之间的指纹ID 。

现在Serial Monitor显示屏中输入ID号，并发送，然后按照屏幕指令提示录入指纹。

把希望录入的手指放在传感器上。

一个手指录入成功后，你也可以按照同样的方式再录入其他几个手指的指纹。

指纹读取代码如下：

#include
int u=0;
int relay=5;

#if (defined(__AVR__) || defined(ESP8266)) && !defined(__AVR_ATmega2560__)
// For UNO and others without hardware serial, we must use software serial...
// pin #2 is IN from sensor (GREEN wire)
// pin #3 is OUT from arduino(WHITE wire)
// Set up the serial port to use softwareserial..
SoftwareSerial mySerial(2, 3);

#else
// On Leonardo/M0/etc, others with hardware serial, use hardware serial!
// #0 is green wire, #1 is white
#define mySerial Serial1

#endif

Adafruit_Fingerprint finger = Adafruit_Fingerprint(&mySerial);

void setup()
{
pinMode(relay,OUTPUT);
Serial.begin(9600);
while (!Serial);// For Yun/Leo/Micro/Zero/...
delay(100);
Serial.println("\n\nAdafruit finger detect test");

// set the data rate for the sensor serial port
finger.begin(57600);
delay(5);
if (finger.verifyPassword()) {
Serial.println("Found fingerprint sensor!");
} else {
Serial.println("Did not find fingerprint sensor : (");
while (1) { delay(1); }
}

Serial.println(F("Reading sensor parameters"));
finger.getParameters();
Serial.print(F("Status: 0x")); Serial.println(finger.status_reg, HEX);
Serial.print(F("Sys ID: 0x")); Serial.println(finger.system_id, HEX);
Serial.print(F("Capacity: ")); Serial.println(finger.capacity);
Serial.print(F("Security level: ")); Serial.println(finger.security_level);
Serial.print(F("Device address: ")); Serial.println(finger.device_addr, HEX);
Serial.print(F("Packet len: ")); Serial.println(finger.packet_len);
Serial.print(F("Baud rate: ")); Serial.println(finger.baud_rate);

finger.getTemplateCount();

if (finger.templateCount == 0) {
Serial.print("Sensor doesn't contain any fingerprint data. Please run the 'enroll' example.");
}
else {
Serial.println("Waiting for valid finger...");
Serial.print("Sensor contains "); Serial.print(finger.templateCount); Serial.println(" templates");
}
}

void loop() // run over and over again
{
getFingerprintID();
delay(50);//don't ned to run this at full speed.
}

uint8_t getFingerprintID() {
uint8_t p = finger.getImage();
switch (p) {
case FINGERPRINT_OK:
Serial.println("Image taken");
break;
case FINGERPRINT_NOFINGER:
Serial.println("No finger detected");
finger.LEDcontrol(FINGERPRINT_LED_OFF, 0, FINGERPRINT_LED_BLUE);
finger.LEDcontrol(FINGERPRINT_LED_OFF, 0, FINGERPRINT_LED_RED);
return p;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
return p;
case FINGERPRINT_IMAGEFAIL:
Serial.println("Imaging error");
return p;
default:
Serial.println("Unknown error");
return p;
}

// OK success!

p = finger.image2Tz();
switch (p) {
case FINGERPRINT_OK:
Serial.println("Image converted");
break;
case FINGERPRINT_IMAGEMESS:
Serial.println("Image too messy");
return p;
case FINGERPRINT_PACKETRECIEVEERR:
Serial.println("Communication error");
return p;
case FINGERPRINT_FEATUREFAIL:
Serial.println("Could not find fingerprint features");
return p;
case FINGERPRINT_INVALIDIMAGE:
Serial.println("Could not find fingerprint features");
return p;
default:
Serial.println("Unknown error");
return p;
}

// OK converted!
p = finger.fingerSearch();
if (p == FINGERPRINT_OK) {
Serial.println("Found a print match!");
finger.LEDcontrol(FINGERPRINT_LED_FLASHING, 25, FINGERPRINT_LED_PURPLE, 10);
delay(1000);
if(u==0)
{
digitalWrite(relay,HIGH);
u=1;
}
else if(u==1)
{
digitalWrite(relay,LOW);
u=0;
}
} else if (p == FINGERPRINT_PACKETRECIEVEERR) {
Serial.println("Communication error");
return p;
} else if (p == FINGERPRINT_NOTFOUND) {
finger.LEDcontrol(FINGERPRINT_LED_FLASHING, 25, FINGERPRINT_LED_RED, 10);
delay(1000);
Serial.println("Did not find a match");
return p;
} else {
Serial.println("Unknown error");
return p;
}

// found a match!
Serial.print("Found ID #"); Serial.print(finger.fingerID);
Serial.print(" with confidence of "); Serial.println(finger.confidence);

return finger.fingerID;
}

// returns -1 if failed, otherwise returns ID #
int getFingerprintIDez() {
uint8_t p = finger.getImage();
if (p != FINGERPRINT_OK)return -1;

p = finger.image2Tz();
if (p != FINGERPRINT_OK)return -1;

p = finger.fingerFastSearch();
if (p != FINGERPRINT_OK)return -1;

// found a match!
Serial.print("Found ID #"); Serial.print(finger.fingerID);
Serial.print(" with confidence of "); Serial.println(finger.confidence);
return finger.fingerID;
} 

一旦指纹录入成功，就可以上传上述代码，以读取存储在指纹数据库中的指纹信息，通过比对匹配实现门禁、考勤、开机等操作。