Circuit Documentation

Summary

This circuit involves an Arduino Mega 2560 and an Arduino UNO microcontroller, interfacing with an NFC/RFID reader (PN532), an SD module, and a fingerprint scanner. The Arduino Mega 2560 is primarily responsible for reading analog values from various sensors, while the Arduino UNO handles communication with the NFC/RFID reader. The SD module is used for data storage, and the fingerprint scanner is used for biometric identification.

Component List

1. Arduino Mega 2560

   • Description: A microcontroller board based on the ATmega2560.
   • Pins: IOREF, RESET, 3V3, 5V, GND, VIN, A0-A15, D21/SCL, D20/SDA, D19/RX1, D18/TX1, D17 PWM/RX2, D16 PWM/TX2, D15/RX3, D14/TX3, D0 RX0, D1 TX0, D2-D13 PWM, AREF, SDA, SCL, D22-D53.

2. Arduino UNO

   • Description: A microcontroller board based on the ATmega328P.
   • Pins: UNUSED, IOREF, Reset, 3.3V, 5V, GND, Vin, A0-A5, SCL, SDA, AREF, D0-D13.

3. NFC/RFID reader PN532

   • Description: A module for reading NFC/RFID tags.
   • Pins: GND, VCC, SDA, SCL, SCK, MISO, MOSI, SS, IRQ, RSTO.

4. SD Module

   • Description: A module for interfacing with SD cards.
   • Pins: CS, SCK, MOSI, MISO, VCC, GND.

5. Fingerprint Scanner

   • Description: A module for fingerprint recognition.
   • Pins: VCC, TX, RX, GND.

Wiring Details

Arduino Mega 2560

• D17 PWM/RX2 connected to Fingerprint Scanner RX
• D16 PWM/TX2 connected to Fingerprint Scanner TX
• D50 connected to SD Module MISO
• D51 connected to SD Module MOSI
• D52 connected to SD Module SCK
• D53 connected to SD Module CS
• 5V connected to Fingerprint Scanner VCC, SD Module VCC
• GND connected to Fingerprint Scanner GND, SD Module GND
• D19/RX1 connected to Arduino UNO D1
• D18/TX1 connected to Arduino UNO D0

Arduino UNO

• D1 connected to Arduino Mega 2560 D19/RX1
• D0 connected to Arduino Mega 2560 D18/TX1
• 5V connected to NFC/RFID reader PN532 VCC
• GND connected to NFC/RFID reader PN532 GND
• D13 connected to NFC/RFID reader PN532 SCK
• D12 connected to NFC/RFID reader PN532 MISO
• D11 connected to NFC/RFID reader PN532 MOSI
• D10 connected to NFC/RFID reader PN532 SS

NFC/RFID reader PN532

• VCC connected to Arduino UNO 5V
• GND connected to Arduino UNO GND
• SCK connected to Arduino UNO D13
• MISO connected to Arduino UNO D12
• MOSI connected to Arduino UNO D11
• SS connected to Arduino UNO D10

SD Module

• MISO connected to Arduino Mega 2560 D50
• MOSI connected to Arduino Mega 2560 D51
• SCK connected to Arduino Mega 2560 D52
• CS connected to Arduino Mega 2560 D53
• VCC connected to Arduino Mega 2560 5V
• GND connected to Arduino Mega 2560 GND

Fingerprint Scanner

• RX connected to Arduino Mega 2560 D17 PWM/RX2
• TX connected to Arduino Mega 2560 D16 PWM/TX2
• VCC connected to Arduino Mega 2560 5V
• GND connected to Arduino Mega 2560 GND

Documented Code

Arduino Mega 2560 Code

#include <Wire.h>
#include <Adafruit_ADS1X15.h>

// Create an ADS1115 object
Adafruit_ADS1115 ads;  // Use default constructor

void setup() {
  Serial.begin(9600);
  
  // Initialize the ADS1115 module
  if (!ads.begin(0x48)) {  // Pass the I2C address here
    Serial.println("Failed to initialize ADS1115.");
    while (1);
  }
  
  Serial.println("ADS1115 initialized.");
}

void loop() {
  // Read analog values from the MQ sensors
  int16_t adc0 = ads.readADC_SingleEnded(0);  // MQ-2 on A0
  int16_t adc1 = ads.readADC_SingleEnded(1);  // MQ-3 on A1
  int16_t adc2 = ads.readADC_SingleEnded(2);  // MQ-7 on A2
  int16_t adc3 = ads.readADC_SingleEnded(3);  // MQ-135 on A3
  
  // Convert ADC values to voltage (optional, for reference)
  float voltage0 = adc0 * 0.1875 / 1000;  // ADS1115 16-bit, ±6.144V range, 0.1875mV per bit
  float voltage1 = voltage0;  // Same for other channels
  float voltage2 = voltage0;
  float voltage3 = voltage0;

  // Print ADC values and voltage to the Serial Monitor
  Serial.print("MQ-2 (A0) ADC: "); Serial.print(adc0);
  Serial.print(", Voltage: "); Serial.print(voltage0); Serial.println(" V");

  Serial.print("MQ-3 (A1) ADC: "); Serial.print(adc1);
  Serial.print(", Voltage: "); Serial.print(voltage1); Serial.println(" V");

  Serial.print("MQ-7 (A2) ADC: "); Serial.print(adc2);
  Serial.print(", Voltage: "); Serial.print(voltage2); Serial.println(" V");

  Serial.print("MQ-135 (A3) ADC: "); Serial.print(adc3);
  Serial.print(", Voltage: "); Serial.print(voltage3); Serial.println(" V");

  // Add delay for readability
  delay(1000);
}

Arduino UNO Code

void setup() {
  // put your setup code here, to run once:

}

void loop() {
  // put your main code here, to run repeatedly:

}

This documentation provides a comprehensive overview of the circuit, including a summary, detailed component list, wiring details, and documented code for the microcontrollers.