Embedded device

Hardware overview

First look at the RFID sensor and the Wemoz

Wiring diagram

Disclaimer: I use my laptop to power my WeMos D1 Mini Pro

This is the first version of the wiring diagram. First version of the wiring diagram

After useing Google to find the right sensor I made the second version of the wiring diagram Second version of the wiring diagram

I added an LCD sensor with a backpack, I did solder the backpack on the LCD. Third version of the wiring diagram

I added an LCD and changed around the wiring. Fourth version of the wiring diagram

Added the LDR sensor. Fifth version of the wiring diagram

Bill of Materials

This is a list of all the materials that I used to complete the blueprint.

Part number/SKU	Manifacturer	Name	Description	Quanitity	Cost	Link
WPI405	Velleman	RFID Sensor	This module allows to both read and write RFID cards.	1	€12,90	https://whadda.com/product/arduino-compatible-rfid-read-and-write-module-wpi405/
HE0369-925	Wemos	WeMos D1 Mini (pro)	Wemos D1 mini V3 is a mini WiFi microcontroller board based on the ESP-8266	1	€10,95	https://www.hobbyelectronica.nl/product/wemos-d1-mini-pro/
000071	Tinytronics	Breadboard 830 points	An electronics breadboard is great for making temporary circuits and prototyping.	1	€4,00	tinytronics.nl/shop/nl/gereedschap-en-montage/prototyping-toebehoren/breadboards/breadboard-830-points
000058	Tinytronics	LCD Display 16*2	Screen display	1	€4,00	https://www.tinytronics.nl/shop/nl/displays/lcd/lcd-display-16*2-karakters-met-witte-tekst-en-blauwe-backlight
161	Adafruit	Photoresistor	CdS cells are little light sensors	1	$0.95	https://www.adafruit.com/product/161#description
EFR-W0P25-A:MF	EDGELEC	Resistor	Regulates volt	1	$0.50	https://www.amazon.com/EDGELEC-Resistor-Tolerance-Resistance-Optional/dp/B07HDGX5LM/ref=sr_1_4?keywords=10k%2Bohm%2Bresistor&qid=1663666242&sr=8-4&th=1
000164	Tinytronics	Jumper wires Male-Male	The DuPont wires are very handy for prototyping, for example, in combination with a breadboard. The different colors make it possible to distinguish the different signals from each other.	20	€0.75	https://www.tinytronics.nl/shop/en/cables-and-connectors/cables-and-adapters/prototyping-wires/dupont-compatible-and-jumper/dupont-jumper-wire-male-male-20cm-10-wires
000066	Arduino	Arduino Uno R3	This Uno R3 is based on the open source design of Arduino, making it both hardware and software compatible with the Arduino ecosystem	1	€12.50	https://www.tinytronics.nl/shop/en/development-boards/microcontroller-boards/arduino-compatible/uno-r3-with-usb-cable
003127	Goobay	Goobay USB-C USB-C	This USB-C USB-C cable makes it possible to connect, synchronize and transfer data with USB-C devices at high speed.	1	€7.00	https://www.tinytronics.nl/shop/en/cables-and-connectors/cables-and-adapters/usb/usb-c/goobay-67976-usb-c-usb-c-3.1-cable-1m-3a-black
HE0153-001	Hobby Electronica	I2C Backpack	With this interface you can control LCD display through the SDA/SCL interface.	1	€1,95	https://www.hobbyelectronica.nl/product/i2c-lcd-interface-voor-16x2-en-20x4-displays/?gclid=EAIaIQobChMI26Wtoouj-gIVK49oCR12hgcJEAQYASABEgKZsPD_BwE
R4,C1	R4,C2

Arduino code

First version of the code

// Libraries
//#include <ESP8266WiFi.h>
//#include <ESP8266HTTPClient.h>
//#include <WiFiClient.h>
#include <MFRC522.h>
#include <ArduinoJson.h>

// define
#define RST_PIN D1 // RST-PIN for RC522 - RFID - SPI - Modul GPIO15 
#define SS_PIN  D8  // SDA-PIN for RC522 - RFID - SPI - Modul GPIO2

MFRC522 mfrc522(SS_PIN, RST_PIN);   // Create MFRC522 instance

void setup() {
  Serial.begin(9600);    // Initialize serial communications
//  WiFi.begin("iotroam", "td7xzadjkk"); //SSID and password

  Serial.print('starting setup');

//    Keep in while-loop while the device is not connected to your accesspoint.
//    while (WiFi.status() != WL_CONNECTED) {
//       delay(1000); // Waiting on connection...
//    }

  SPI.begin();           // Init SPI bus
  mfrc522.PCD_Init();    // Init MFRC522 
}


// Helper routine to dump a byte array as hex values to Serial
void dump_byte_array(byte *buffer, byte bufferSize) {
    for (byte i = 0; i < bufferSize; i++) {
        Serial.print(buffer[i] < 0x10 ? " 0" : " ");
        Serial.print(buffer[i], HEX);
    }
}

String get_byte_array (byte *buffer, byte bufferSize) { 
      String UID = "";
      for (byte i = 0; i < bufferSize; i++) {
        buffer[i] < 0x10 ? " 0" : " ";
        char myHex[10] = "";
        ltoa(buffer[i],myHex,16); //convert to c string base 16
        UID += String(myHex);
        UID+=" ";
      }
      UID.toUpperCase();
      return UID;
}

void loop() {

    //wifi
//    WiFiClient client;
//    HTTPClient httpClient;
//
//    String serverPath = "http://43e4e4e4279616.lhr.life/insert.php?cardUID=" + get_byte_array(mfrc522.uid.uidByte, mfrc522.uid.size);
//    httpClient.begin(client, serverPath);
//    int httpCode = httpClient.GET();
//
//    Serial.print('starting wifi');
//
//    if(httpCode == HTTP_CODE_OK) { // HTTP_CODE_OK == 200
//      String payload = httpClient.getString();
//      Serial.println(payload);
//    } else {
//      Serial.println("Unable to connect :(");
//    }


    // Look for new cards
    if ( ! mfrc522.PICC_IsNewCardPresent()) {
        delay(50);
        return;
    }

    // Select one of the cards
    if ( ! mfrc522.PICC_ReadCardSerial()) {
        delay(50);
        return;
    }

    // Show some details of the PICC (that is: the tag/card)
    Serial.print(F("Card UID:"));
    Serial.println(get_byte_array(mfrc522.uid.uidByte, mfrc522.uid.size));   
    Serial.println();

    delay(1000);
}

This is the first version of code, with wifi and RFID scanner, with all the code that does work switched on. This is an older version, down below is the complete code that I will update.

For the other two sensors, this is the code I used.

#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x27, 16, 2);

void setup()
{
    // initialize the LCD
    lcd.begin();

   // Turn on the blacklight and print a message.
    lcd.backlight();
    lcd.setCursor(0, 0);
    lcd.print("Hello, world!");

    Serial.begin(115200);
    Serial.println("test");

}

void loop()
{
    // Do nothing here...
}

This is the code for de LDR that I am using.

#define LDRpin A0 // pin where we connected the LDR and the resistor

int LDRValue = 0;     // result of reading the analog pin

void setup() {
  Serial.begin(9600); // sets serial port for communication
}

void loop() {
  LDRValue = analogRead(LDRpin); // read the value from the LDR
  Serial.println(LDRValue);      // print the value to the serial port
  delay(1500);                    // wait a little, this was originally 100, but I put it to 1500 so my serial monitor would not be overloaded with small data.
}

Current Arduino code

//Wifi manager
//#include <WiFiManager.h>

// Wifi
#include <ESP8266WiFi.h>
#include <ESP8266HTTPClient.h>
#include <WiFiClient.h>
#include <ESP8266WebServer.h>

//RFID scanner
#include <MFRC522.h>
#include <ArduinoJson.h>

//LCD
#include <Wire.h>
#include <LiquidCrystal_I2C.h>

// Set the LCD address to 0x27 for a 16 chars and 2 line display
LiquidCrystal_I2C lcd(0x27, 16, 2);

// define
#define RST_PIN D0 // RST-PIN for RC522 - RFID - SPI - Modul GPIO15 
#define SS_PIN  D8  // SDA-PIN for RC522 - RFID - SPI - Modul GPIO2

MFRC522 mfrc522(SS_PIN, RST_PIN);   // Create MFRC522 instance



void setup() {
  Serial.begin(115200);    // Initialize serial communications
  //WiFi.begin("iotroam", "cwfwl1qb6t"); //SSID and password
  WiFi.begin("meterkastwlan", "288Ea72870"); //SSID and password

  Serial.print("starting setup");

//    Keep in while-loop while the device is not connected to your accesspoint.
    while (WiFi.status() != WL_CONNECTED) {
       Serial.println("Waiting for connection status=" + String(WiFi.status()));
       delay(1000); // Waiting on connection...
    }
       Serial.println("Connected! status=" + String(WiFi.status()));

  SPI.begin();           // Init SPI bus
  mfrc522.PCD_Init();    // Init MFRC522 


 // initialize the LCD
    lcd.begin();

   // Turn on the blacklight and print a message.
    lcd.backlight();
    lcd.print("Hello, world!");



}


// Helper routine to dump a byte array as hex values to Serial
void dump_byte_array(byte *buffer, byte bufferSize) {
    for (byte i = 0; i < bufferSize; i++) {
        Serial.print(buffer[i] < 0x10 ? " 0" : " ");
        Serial.print(buffer[i], HEX);
    }
}

String get_byte_array (byte *buffer, byte bufferSize) { 
      String UID = "";
      for (byte i = 0; i < bufferSize; i++) {
        buffer[i] < 0x10 ? " 0" : " ";
        char myHex[10] = "";
        ltoa(buffer[i],myHex,16); //convert to c string base 16
        UID += String(myHex);
        UID+=" ";
      }
      UID.toUpperCase();
      return UID;

}




void loop() {

      // Look for new cards
    if ( ! mfrc522.PICC_IsNewCardPresent()) {
        delay(50);
        return;
    }

    // Select one of the cards
    if ( ! mfrc522.PICC_ReadCardSerial()) {
        delay(50);
        return;
    }

    // Show some details of the PICC (that is: the tag/card)
    Serial.print("Card UID:");
    Serial.println(get_byte_array(mfrc522.uid.uidByte, mfrc522.uid.size));   
    Serial.println();

    delay(1000);


    //wifi
    WiFiClient client;
    HTTPClient httpClient;

    /*String serverPath = "http://ip/insert.php?cardUID=" + get_byte_array(mfrc522.uid.uidByte, mfrc522.uid.size);
    httpClient.begin(client, serverPath);
    int httpCode = httpClient.GET();

    Serial.print(serverPath);

    //Serial.print("starting wifi");

     if(httpCode == HTTP_CODE_OK) { // HTTP_CODE_OK == 200
      String payload = httpClient.getString();
      Serial.println(payload);
    } else {
      Serial.println("Unable to connect :(");
    }*/

    String url = String("http://ip/insert.php?cardUID=") + get_byte_array(mfrc522.uid.uidByte, mfrc522.uid.size);
    Serial.println(url);
    if (httpClient.begin(client, url)) {

    //start connection and send HTTP header
    int httpCode = httpClient.GET();

    if(httpCode == HTTP_CODE_OK) { // HTTP_CODE_OK == 200
      String payload = httpClient.getString();
      Serial.println(payload);
    } else {
      Serial.println("Unable to connect :(");
    }

    delay(500);
    }



}

Errors

Java error

During the process of tying all my code together I got this error/issue :

I asked 2 teachers for help, but they could not figure out what was wrong. Google didn’t help. Restarting laptop didn’t work. Nothing worked. This prevents me from working on my code any further.

Things I tried to fix it: - Restarting laptop - Restaring arduino - One by one turning off code to see if the error was still there

After those things did not work for me a classmate connected my WeMos to their laptop and tested a simple script.

void setup() {
  Serial.begin(9600);
  Serial.print("starting setup");

}

void loop() {
  Serial.print("this is loop");
  delay(1000);
}

That worked on their laptop and we did not get the error with java. Then I re-connected the WeMos to my laptop and ran the same script. After that I did not get the error anymore. We also ran all my code on their laptop through my WeMos and that did also not give an error.

Wifi

I also had a problem with connecting my wifi to the school’s hot spot. I highly recommend using your own wifi at home or using your phone as a hot spot. It is not that secure, but for a small project like this it is fine for me.

Links

• https://www.instructables.com/WiFi-RFID-Reader/
• https://randomnerdtutorials.com/esp8266-pinout-reference-gpios/
• https://microdigisoft.com/how-to-use-i2c-lcd-with-esp8266-wemos-d1-mini/
• https://www.tweaking4all.com/hardware/arduino/arduino-light-sensitive-resistor/

---

Last update: October 19, 2022