/*
1. click the breakout circuit board (custom chip)
2. Slide the UID generator slider
3. Press the Green Button for sending data

Note: I am writing a code that supports MFRC522 library, 
but I can't make it work,
so here's the link: https://wokwi.com/projects/423914137980242945

(c) 2025, James Balolong 
*/

#include <SPI.h>
#define CS 5  // Chip Select pin connected to the custom chip's CS pin

void setup() {
  // Initialize Serial for debugging
  Serial.begin(115200);
  
  // Configure CS pin as output and set it high initially
  pinMode(CS, OUTPUT);
  digitalWrite(CS, HIGH);
  
  // Initialize SPI with default pins (SCK: 18, MISO: 19, MOSI: 23)
  SPI.begin();
  Serial.println("ESP32 SPI initialized, waiting for UID...");
}

void loop() {
  uint8_t buffer[4] = {0};  // Buffer to store the 4-byte UID
  
  // Start an SPI transaction
  digitalWrite(CS, LOW);        // Pull CS low to enable the slave
  SPI.transfer(buffer, 4);      // Perform a 4-byte transfer, reading data into buffer
  digitalWrite(CS, HIGH);       // Pull CS high to end the transaction
  
  // Check if any data was received (not all zeros, assuming UID isn't 0x00 0x00 0x00 0x00)
  if (buffer[0] != 0 || buffer[1] != 0 || buffer[2] != 0 || buffer[3] != 0) {
    Serial.print("Received UID: ");
    for (int i = 0; i < 4; i++) {
      Serial.print("0x");
      // Add leading zero for single-digit hex values
      if (buffer[i] < 16) Serial.print("0");
      Serial.print(buffer[i], HEX);
      Serial.print(" ");
    }
    Serial.println();
  }
  
  // Small delay to prevent overwhelming the Serial Monitor
  delay(100);
}