Example Code for Arduino-Demo for Low-power Mode

Hardware Preparation

• DFRduino Leonardo (or similar) x 1
• Capacitive Fingerprint Sensor - UART (FPC Connector) × 1
• DuPont Wires

Software Preparation

• Arduino IDE
• Download and install the ID809 Library. (About how to install the library?)

Wiring Diagram

Sample Code

• Control Pin VIN via relay to let the fingerprint module enter low-power mode.

• How to enter sleep mode: first send entersleepstation (), then disconnect the VIN power supply (at this time, the module current is below 10uA)

• How to wake up: when the maincontroller monitors that there is a pulse signal output from the Pin IRQ(the IRQ pin will generate a pulse signal when the finger is pressed on the fingerprint module), supply power to the VIN, and determine if the module communicates properly by fingerprint.isConnected(), if so, then it could work well.

/*!
 * @file Demo for low power mode.ino
 * @brief Control Pin VIN via relay to let the Fingerprint module enter low power mode
 * @n Experiment Phenomenon：If there is no finger pressing for 10s, the mdoule enters sleep mode. Press your finger on the sensor to exit the sleep mode and the light ring lights up.
 * @copyright  Copyright (c) 2010 DFRobot Co.Ltd (https://www.dfrobot.com)
 * @licence     The MIT License (MIT)
 * @author [Eddard]([email protected])
 * @version  V1.0
 * @date  2021-08-20
 * @get from https://www.dfrobot.com
 * @url https://github.com/DFRobot/DFRobot_ID809
*/
#include <DFRobot_ID809.h>

#define IRQ    6
#define RELAY  7

/*Use software serial when using UNO or NANO*/
#if ((defined ARDUINO_AVR_UNO) || (defined ARDUINO_AVR_NANO))
    #include <SoftwareSerial.h>
    SoftwareSerial Serial1(2, 3);  //RX, TX
    #define FPSerial Serial1
#else
    #define FPSerial Serial1
#endif

DFRobot_ID809 fingerprint;

long long curr = 0;
uint8_t sleepFlag = 1;

void setup(){
  /*Init print serial port */
  Serial.begin(9600);
  /*Init FPSerial*/
  FPSerial.begin(115200);
  /*Take FPSerial as communication port of fingerprint module */
  fingerprint.begin(FPSerial);
  /*Wait for Serial to open*/
  pinMode(RELAY, OUTPUT);
  digitalWrite(RELAY, HIGH);
  delay(100);  //Delay 100ms to wait for the start of the module
  while(!Serial);
  /*Test whether device can communicate properly with mainboard 
    Return true or false
    */
  while(fingerprint.isConnected() == false){
    Serial.println("Communication with device failed, please check connection");
    delay(1000);
  }
  Serial.println("Module init succeeds, enter sleep mode when no finger pressed for 10s");
  fingerprint.ctrlLED(/*LEDMode = */fingerprint.eBreathing, /*LEDColor = */fingerprint.eLEDBlue, /*blinkCount = */0);
}

void loop(){
  if(digitalRead(IRQ) && (sleepFlag == 0)){
    digitalWrite(RELAY, HIGH);
    Serial.println("Exit sleep mode");
    delay(100);  //Delay 100ms to wait for the start of the module
    curr = millis();
    sleepFlag = 1;
    if(fingerprint.isConnected() == true){
      Serial.println("Module communication back to normal");
      fingerprint.ctrlLED(/*LEDMode = */fingerprint.eBreathing, /*LEDColor = */fingerprint.eLEDBlue, /*blinkCount = */0);
    } else{
      Serial.println("Module communication recovery failed");
    }
  }
  if((sleepFlag == 1)&&(millis() - curr > 10000)){
    fingerprint.enterStandbyState();  //Let your module enter standby module first, then disconnect VIN power
    digitalWrite(RELAY, LOW);
    sleepFlag = 0;
    Serial.println("Enter sleep mode");
  }
}

Result

If there is no finger pressing for 10s, the mdoule enters sleep mode. Press your finger on the sensor to exit the sleep mode and the light ring lights up.