R200 reader module with ESP32, not getting the expected output

Projects General Guidance
1

Hi, greetings everyone. I'm currently working on my final year project which I'm using UHF RFID reader (YPD-R200), AC voltage LM358 V3 volt sensor to measure tx or rx volt, ESP32 as microcontroller, UHF on-metal RFID tags and LCD for output display. The project concept is when reader reads the tag's epc code which was updated in database, esp32 will convert the hexa and lcd will display the output ( Manhole ID, Owner) while i want serial monitor to have measured volt.

#include <WiFi.h>
#include <HTTPClient.h>
#include <LiquidCrystal_I2C.h> 
#include <HardwareSerial.h>

const char* ssid = "-------2.4GHz";             // Your WiFi SSID
const char* password = "-------";     // Your WiFi Password

#define RXD2 16  
#define TXD2 17 

LiquidCrystal_I2C lcd(0x27, 16, 2);
HardwareSerial rfidSerial(2);

String lastTag = "";
unsigned long lastSeen = 0;

void setup() {
  Serial.begin(115200);
  rfidSerial.begin(115200, SERIAL_8N1, RXD2, TXD2);

  lcd.init();
  lcd.backlight();
  lcd.setCursor(0, 0);
  lcd.print("Connecting WiFi");

  WiFi.begin(ssid, password);
  while (WiFi.status() != WL_CONNECTED) {
    delay(500);
    Serial.print(".");
  }
  Serial.println("Connected.");
  lcd.clear();
  lcd.print("Scan tag...");
}

void loop() {
  static String buffer = "";

  while (rfidSerial.available()) {
    char c = rfidSerial.read();
    buffer += c;

    if (buffer.length() > 128)
      buffer = buffer.substring(buffer.length() - 64);

    if (buffer.length() >= 24) {
      String epc = parseEPC(buffer);
      if (epc.length() == 24 && epc != lastTag && epc != "000000000000000000000000") {
        lastTag = epc;
        lastSeen = millis();
        Serial.println("Detected EPC: " + epc);
        fetchTagInfo(epc);
        buffer = "";
      }
    }
  }

  if (millis() - lastSeen > 5000 && lastTag != "") {
    lcd.clear();
    lcd.setCursor(0, 0);
    lcd.print("Scan tag...");
    lastTag = "";
  }
}

String parseEPC(const String &raw) {
  String hexStr = "";
  for (int i = 0; i < raw.length(); i++) {
    byte b = (byte)raw[i];
    if (b < 0x10) hexStr += "0";
    hexStr += String(b, HEX);
  }
  hexStr.toUpperCase();

  if (hexStr.length() >= 24) {
    return hexStr.substring(hexStr.length() - 24);
  }
  return "";
}

void fetchTagInfo(String epc) {
  if (WiFi.status() == WL_CONNECTED) {
    HTTPClient http;
    String url = "http://192.----------/get_tag_info.php?epc=" + epc;
    http.begin(url);
    int httpCode = http.GET();

    if (httpCode > 0) {
      String payload = http.getString();
      Serial.println(payload);
      // Parse JSON and display on LCD
      int ownerIdx = payload.indexOf("\"owner\":\"");
      int descIdx = payload.indexOf("\"description\":\"");
      if (ownerIdx > -1 && descIdx > -1) {
        String owner = payload.substring(ownerIdx + 9, payload.indexOf("\"", ownerIdx + 9));
        String description = payload.substring(descIdx + 15, payload.indexOf("\"", descIdx + 15));
        lcd.clear();
        lcd.setCursor(0, 0);
        lcd.print("Owner: " + owner);
        lcd.setCursor(0, 1);
        if (description.length() > 16) description = description.substring(0, 16);
        lcd.print(description);
      } else {
        lcd.clear();
        lcd.print("Tag not found");
      }
    } else {
      Serial.println("Error on HTTP: " + String(httpCode));
      lcd.clear();
      lcd.print("HTTP error");
    }
    http.end();
  } else {
    Serial.println("WiFi not connected");
    lcd.clear();
    lcd.print("WiFi Disconnect");
  }
}

but when reader is initiated lcd shows unknown tags while serial monitor shows variety of detected epc and which is not from the tag that i have. Can anyone help me please?

2

Please edit your post, select each of the codes (one at a time) and click the < CODE > button to apply so-called code tags and next save your post. It makes it easier to read, easier to copy and the forum software will display it correctly.

how do you power the system?
can you upload a schematic showing the wiring and power supplies?

1 Like
3

I have edited the post and code sir. Reader gets 5v from esp32 (expansion board). RXD from reader to esp32 TX2 (gpio17) and TXD to esp32 RX2(gpio16).

circuit_image
circuit_image1920×1480 255 KB

Here's the schematic sir.