Hi everyone,
I have had my Arduino Uno for some months now and I am currently developing a 'credit card' payment system using RFID tags.
I am using an LCD screen, a keypad, the RFID sensor, and a buzzer and the program is working really well. Each card corresponds to a specific serial number and a user can add money to his account or buy items.
Now I want to post the money left in the account to a database every time a user makes a purchase. I then want to access the data using SQL and display on a website.
Would this be possible using ESP8266? I am not quite sure how you are supposed to send data to a database...
Kind regards and thank you in advance 
p.s. here is the code for my current program which stores the data locally.
#include <LiquidCrystal_I2C.h>
#include <Wire.h>
#include <SPI.h>
#include <MFRC522.h>
#include <Keypad.h>
const byte ROWS = 4; //four rows
const byte COLS = 4; //three columns
char keys[ROWS][COLS] = {
{'1','2','3','A'},
{'4','5','6','B'},
{'7','8','9','C'},
{'*','0','#','D'}
};
float nums[5] ={};
byte rowPins[ROWS] = {8, 7, 6, 5}; //connect to the row pinouts of the keypad
byte colPins[COLS] = {A3, A2, A0, A1}; //connect to the column pinouts of the keypad
int decimal =0;
LiquidCrystal_I2C lcd = LiquidCrystal_I2C(0x27, 16, 2);
Keypad keypad = Keypad( makeKeymap(keys), rowPins, colPins, ROWS, COLS );
byte ledPin = 13;
#define RST_PIN 9 // Configurable, see typical pin layout above
#define SS_PIN 10 // Configurable, see typical pin layout above
float price = 0;
char MoneyLeft = 10;
MFRC522 mfrc522(SS_PIN, RST_PIN);
String value = "A9 A4 DE 8B";// Create MFRC522 instance
float cost = 0;
int c = 0;
boolean add =false;
int rs = 7;//lcd screen
int en=8;
int d4 = 3;
int d5= 4;
int d6= 5;
int d7 = 6;//lcd screen
int buzzPin = 2;
int buzztime = 500;
int t= 0;
float addition = 0;
const int buzzer =2;
boolean entered[4] = {};
String thirdscan;
String lastscan;
String serialnumbers[] = {"A9 A4 DE 8B", "0A FA 82 16"};
String names[] = {"Alex", "Marta"};
float account[] = {10, 20};
bool schoolLunch[] = {true, false};
void setup() {
Serial.begin(9600); // Initialize serial communications with the PC
while (!Serial); // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
SPI.begin();
lcd.init();
lcd.backlight();// Init SPI bus
mfrc522.PCD_Init(); // Init MFRC522
mfrc522.PCD_DumpVersionToSerial(); // Show details of PCD - MFRC522 Card Reader details
Serial.println(F("Scan PICC to see UID, SAK, type, and data blocks..."));
pinMode(buzzer, OUTPUT);
}
void loop() {
// Reset the loop if no new card present on the sensor/reader. This saves the entire process when idle.
lcd.setCursor(0,0);
// Look for new cards
if ( ! mfrc522.PICC_IsNewCardPresent())
{
return;
}
// Select one of the cards
if ( ! mfrc522.PICC_ReadCardSerial())
{
return;
}
//Show UID on serial monitor
Serial.print("UID tag :");
String content= "";
byte letter;
for (byte i = 0; i < mfrc522.uid.size; i++)
{
Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
Serial.print(mfrc522.uid.uidByte[i], HEX);
content.concat(String(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " "));
content.concat(String(mfrc522.uid.uidByte[i], HEX));
}
Serial.println();
content.toUpperCase();
for (c = 0; c <= 1; c++){
if (content.substring(1) == serialnumbers[c]) //change here the UID of the card/cards that you want to give access
{
tone(buzzer, 1600);
delay(100);// ...for 1 sec
noTone(buzzer);
lcd.clear();
if (lastscan != content.substring(1)){
lcd.print(names[c]);
lcd.print("'s account:");
lcd.setCursor(0,1);
lcd.print(account[c]);
delay(1500);
lcd.clear();
lcd.print("Scan again to");
lcd.setCursor(0,1);
lcd.print("buy something...");
}
else{
lcd.clear();
delay(50);
Serial.print("How much does this cost");
lcd.print("Item Cost: ");
lcd.setCursor(0,1);
int c=0;
int key=0;
float price = 0;
int decimal = 0;
int z=1;
boolean add=false;
for (z=1;z<=4;z++){
nums[z] = 0;
entered[z] = false;
}
for (int x=1; x<=4; x++){
int key = keypad.getKey();
while(key == NO_KEY) {
key = keypad.getKey();
}
if (key >= 48 and key<=57){
key = key-48;
nums[x] = key;
entered[x] = true;
}
else{
if (key==42){
decimal =x;
}
if (key==65){
add=true;
break;
}
if (key==35){
break;
}
}
if (x-decimal==1 and decimal > 0){
nums[x] = nums[x]/10 ;
}
if (x-decimal==2 and decimal > 0){
nums[x] = nums[x]/100 ;
}
if (decimal == 0 and x ==2){
nums[1] = nums[1]*10;
}
if (entered[x]){
Serial.print(key);
}
else{
if (decimal==x){
}
}
}
int x=1;
for (x=1;x<=4;x++){
price += nums[x];
}
Serial.println();
if (add==false){
lcd.setCursor(0,1);
lcd.print(price);
Serial.println(price);
}
if (add==true) {
lcd.clear();
lcd.print ("How much do");
lcd.setCursor(0,1);
lcd.print("you want to add?");
for (int x=1; x<=4; x++){
int key = keypad.getKey();
while(key == NO_KEY) {
key = keypad.getKey();
}
if (key >= 48 and key<=57){
key = key-48;
nums[x] = key;
entered[x] = true;
}
else{
if (key==42){
decimal =x;
}
if (key==65){
add=true;
break;
}
if (key==35){
break;
}
}
if (x-decimal==1 and decimal > 0){
nums[x] = nums[x]/10 ;
}
if (x-decimal==2 and decimal > 0){
nums[x] = nums[x]/100 ;
}
if (decimal == 0 and x ==2){
nums[1] = nums[1]*10;
}
if (entered[x]){
Serial.print(key);
lcd.print(key);
}
else{
if (decimal==x){
lcd.print(".");
}
}
}
if (decimal==3){
nums[1] = nums[1]*10;
}
int x =1;
for (x=1;x<=4;x++){
addition += nums[x];
}
lcd.clear();
lcd.print("Money added:");
lcd.setCursor(0,1);
lcd.print(addition);
account[c] += addition;
delay(1500);
lcd.clear();
lcd.print("Money in account:");
lcd.setCursor(0,1);
Serial.println(account[c]);
lcd.print(account[c]);
delay(1500);
lcd.clear();
lcd.setCursor(4,0);
lcd.print("Success!");
addition = 0;
}
else{
delay(1500);
lcd.clear();
float money = account[c];
if (money - price >= 0){
float (money -= price);
account[c] = (float)money;
Serial.println();
Serial.println(money);
lcd.print("Money left: ");
lcd.setCursor(0,1);
lcd.print(money);
delay(1500);
lcd.clear();
lcd.setCursor(4,0);
lcd.print("Success!");
}
else{
lcd.print("Not enough");
lcd.setCursor(0,1);
lcd.print("money in account");
}
}
}
}
}
thirdscan = lastscan;
lastscan = content.substring(1);
content.substring(1) ="";