This is a sketch that allows the ATtiny line of micro controllers to interface with the GT511-C1/3 fingerprint sensor from Sparkfun. The advantage of this sketch is that it requires no libraries and thus works on any board that can be programmed with the Arduino IDE. The sketch initializes the connection with the sensor, turns the sensors in-bui…

GT511-C1 and ATtiny

#define greenLed 4 //this lights up when a registered user places their thumb
#define redLed 3 //this is on until a registerd user places their thumb
#define relay 2 //this pin goes HIGH when the registered thumb is placed
#define rxPin 0 //this goes to the TX pin of the FP sensor
#define txPin 1 //this goes to the RX pin of the FP sensor

#include <SoftwareSerial.h>;
SoftwareSerial mySerial(rxPin, txPin);

byte zero = 0;
byte highbyte = 0;
byte lowbyte = 0;
byte command = 1;
word checksum = 0;
byte highcheck = 0;
byte lowcheck = 0;
char inData[20]; // Allocate some space for the string
char correctData[] = {
};
char inChar; // Where to store the character read
int index = 0; // Index into array; where to store the character
boolean ledon = false;
int phase = 1;
boolean on = false;

void setup() {
  //Serial.begin(9600);
  //Serial.println("Start");
  mySerial.begin(9600);
  pinMode(greenLed,OUTPUT);
  pinMode(redLed,OUTPUT);
  pinMode(relay,OUTPUT);
  inito();
}
//Here comes the part you want to put in void loop that sends the command to the device
boolean correctFinger=false;
unsigned int param;
void loop(){
  if (phase == 1){
    if(nbWait(200)){
      //Serial.print("please place finger");
      communicate(67,48);
    }
  }
  if(mySerial.available()){
    while(mySerial.available() > 0){
      inChar = mySerial.read(); // Read a character
      if(inChar == 0x55){//reset index if startbyte
        index = 0;
      }
      //Serial.print("index: ");
      //Serial.print(index);
      //Serial.print(" ");
      //Serial.print("Byte: ");
      //Serial.println(inChar, HEX);
      inData[index] = inChar;//save indexed character to array    

      if(index == 11){
        //Serial.println("end of packet");
        //look at response byte to check if ACK or NACK
        if(inData[8] == 0x30){    
          //Serial.println("Acknowledge");
          //different actions if acknowledged
          getParams();
          switch (phase){
          case 1:
            //phase 2 here (identification)
            //Serial.println("finger pressed");
            phase = 2;
            communicate(73,0);
            break;
          case 2:
            //phase 2 here (accepted identification)
            phase = 3;
            //Serial.print("Print ");
            //Serial.print(param);
            //Serial.println(" Identified, Broom broom");
            if(!on){
              digitalWrite(greenLed,HIGH);
              digitalWrite(redLed,LOW);
              digitalWrite(relay,HIGH);
              on = true;
              delay(1500);//time to take finger off sensor
            }
            else{
              digitalWrite(greenLed,LOW);
              digitalWrite(redLed,HIGH);
              digitalWrite(relay,LOW);
              on = false;
              delay(1500);
            }
            phase = 1;//back to beginning
            break;
          }

        }
        else{
          //Serial.println("Non-Acknowledge");
          getParams();
          switch (phase){
          case 2:
            //phase 3 here (denied identification)
            //Serial.println("Nice try kiddo");
            if(!on){
              digitalWrite(redLed,LOW);
              delay(100);
              digitalWrite(redLed,HIGH);
            }
            else{
              digitalWrite(redLed,HIGH);
              delay(100);
              digitalWrite(redLed,LOW);
            }
            //red led on
            phase = 1;
            break;
          }
        }
      }
      index++;
    }
  }
}

void getParams(){
  param = (unsigned int)word(inData[5],inData[4]);
  //Serial.print("Param: ");
  //Serial.println(param);
}

void communicate(int com, int val){
  int value;
  switch(val){
  case 48:
    value = 0;
    break;

  case 49:
    value = 1;
    break; 

  case 50:
    value = 2;
    break;

  case 51:
    value = 3;
    break; 

  case 52:
    value = 4;
    break;

  case 53:
    value = 5;
    break;

  case 54:
    value = 6;
    break;

  case 55:
    value = 7;
    break;

  case 56:
    value = 8;
    break;

  case 57:
    value = 9;
    break;
  }
  switch(com){
    // 0 > init > 01
  case 48:
    //Serial.println("Open connection");
    command = 0x01;
    break;

    // X > close > 02
  case 88:
    //Serial.println("Close connection");    
    command = 0x02;
    break;

    // L > LED change > 12  
  case 76:
    if(value == 0){
      //Serial.println("LED off");
    } 
    else {
      //Serial.println("LED on");
    }
    command = 0x12;
    break;

    // T > Check total enrol count > 20 
  case 84:
    //Serial.println("Check total enrol count");
    command = 0x20;
    break;

    // t > check enrol id  > 21
  case 116:
    //Serial.print("Check enrol for ID ");
    //Serial.println(value);
    command = 0x21;
    break;  

    // E > enrol1 > 22
  case 69:
    //Serial.print("Begin enrol for ID ");
    //Serial.println(value);      
    command = 0x22;
    break;

    // 1 > enrol1 > 23
  case 49:
    //Serial.println("Enrol scan #1"); 
    command = 0x23;
    break;  

    // 2 > enrol2 > 24  
  case 50:
    //Serial.println("Enrol scan #2"); 
    command = 0x24;
    break;

    // 3 > enrol3 > 25  
  case 51:
    //Serial.println("Enrol scan #3");  
    command = 0x25;
    break;

    // F > isfingerpressed? > 26 
  case 70:
    //Serial.println("Checking if finger pressed..."); 
    command = 0x26;
    break;

    // d > delete ID > 40
  case 100:
    //Serial.print("Deleting scan ");
    //Serial.println(value);
    command = 0x40;
    break;

    // D > delete all > 41
  case 68:
    //Serial.println("Deleting all scans"); 
    command = 0x41;
    break;

    // V > verify ID > 50
  case 86:
    //Serial.print("Verfifying ID ");
    //Serial.println(value);
    command = 0x50;
    break;

    // I > identify finger > 51
  case 73:
    //Serial.println("Checking for scan match...");
    command = 0x51;
    break;

    // C > capture finger > 60
  case 67: 
    //Serial.println("Capturing finger");
    command = 0x60;
    break; 

    // Y > ack > 30
  case 89:
    //Serial.println("Sending acknowledgement");
    command = 0x30;
    break;

    // N > nack > 31
  case 78:
    //Serial.println("Sending Non-acknowledgement");
    command = 0x31;
    break; 

  }

  //command = 0x12; //The command goes here. This is the command for the LED.
  valueToWORD(value); //This value is the parameter being send to the device. 0 will turn the LED off, while 1 will turn it on.
  calcChecksum(command, highbyte, lowbyte); //This function will calculate the checksum which tells the device that it received all the data
  mySerial.write(0x55); //Command start code 1
  mySerial.write(0xAA); //Command start code 2
  mySerial.write(0x01); // This is the first byte for the device ID. It is the word 0x0001
  mySerial.write(zero); // Second byte of Device ID. Notice the larger byte is first. I'm assuming this is because the datasheet says "Multi-byte item is represented as Little Endian"
  mySerial.write(lowbyte); //writing the largest byte of the Parameter
  mySerial.write(highbyte); //Writing the second largest byte of the Parameter
  mySerial.write(zero); //The datasheet says the parameter is a DWORD, but it never seems to go over the value of a word
  mySerial.write(zero); //so I'm just sending it a word of data. These are the 2 remaining bytes of the Dword
  mySerial.write(command); //write the command byte
  mySerial.write(zero); //again, the commands don't go over a byte, but it is sent as a word, so I'm only sending a byte
  mySerial.write(lowcheck); //Writes the largest byte of the checksum
  mySerial.write(highcheck); //writes the smallest byte of the checksum
}
//Now for the functions

void valueToWORD(int v){ //turns the word you put into it (the paramter in the code above) to two bytes
  highbyte = highByte(v); //the high byte is the first byte in the word
  lowbyte = lowByte(v); //the low byte is the last byte in the word (there are only 2 in a word)
}

void calcChecksum(byte c, byte h, byte l){
  checksum = 256 + c + h + l; //adds up all the bytes sent
  highcheck = highByte(checksum); //then turns this checksum which is a word into 2 bytes
  lowcheck = lowByte(checksum);
}
boolean goOn = true;
void inito(){
  communicate(48, 48); 
  while(goOn){
    if(mySerial.available()){
      while(mySerial.available() > 0){
        inChar = mySerial.read(); // Read a character
        if(inChar == 0x55){//reset index if startbyte
          index = 0;
        }
        //Serial.print("index: ");
        //Serial.print(index);
        //Serial.print(" ");
        //Serial.print("Byte: ");
        //Serial.println(inChar, HEX);
        inData[index] = inChar;//save indexed character to array    

        if(index == 11){
          //Serial.println("end of packet");
          //look at response byte to check if ACK or NACK
          if(inData[8] == 0x30){
            for(int u=0;u<sizeof(inData);u++){
              inData[u] = 0;
            }
            //Serial.println("Acknowledge");
            switch(phase){
            case 1:
              //phase 2 starts here
              phase = 2;//next part of ze plan
              communicate(76, 49);
              break;
            case 2:
              phase = 3;
              goOn=false;
              break;
            }
          }  
          else{
            //Serial.println("Non-Acknowledge");
          }
        }
        index++;
      }
    }
    // read from port 0, send to port 1:
  }//
  phase = 1;
  digitalWrite(redLed,HIGH);
}
boolean first = true;
unsigned long sTime;
boolean nbWait(long waitTime){
  if(first){
    first = false;
    sTime = millis();
  }
  if (millis() - sTime >= waitTime){
    first = true;
    return true;
  }
  else{
    return false;
  }
}