I have an RFID reader: http://img.tradeindia.com/fp/1/641/264.jpg

Something like above along with ITEAD TFT shield & GSM Modem. The RFID reader has an RS-232 port as well as GND, TX and 5V pins. I am using an Arduino Mega 2560 board. I have connected the TX, GND of RFID reader to RX3 pin 15 / GND (pin) of Arduino. Note I am supplying 12 V to RFID via an adapter.

Note the ITEAD TFT shield consumes the TX0, RX0 pins—so I cannot make use of the RX0 and TX0 pins. Though I have not written the code for GSM modem.

Now while running the program below, I am getting junk output both in my TFT display as well as the serial monitor:

#define __AVR__
#include <UTFT.h>

// Declare which fonts we will be using
extern uint8_t SmallFont[];
extern uint8_t BigFont[];
extern uint8_t SevenSegNumFont[];
UTFT myGLCD(ITDB24,59,58,57,56);
String myString = "";

void setup() {

void loop() {
  if (Serial3.available()) {
    int inByte = Serial3.read();
     myString += String(inByte);
    if(myString.length() == 10)
      myGLCD.print(myString, CENTER, 0);

TFT Screen output:


Serial Monitor Output: non printable junk character.

The value is incorrect, I am pretty sure, what am I doing wrong?

I found that the ITEAD shield is sending or rather using RX0/TX0 pins very frequently—some data is going through.

BTW what is the functionality of http://arduino.cc/en/Tutorial/SoftwareSerialExample?

How can I use 3 different Serial I/Os individually at the same time without disturbing any other I/O?

2 Answers 2


First of all, try testing 1 functionality at a time to isolate the issue. Now you do not know if the LCD is not working correctly, or if the serial communication with the RFID module is not working correctly. Connect it to a computer and test both independently.

When getting gibberish from a serial line, usually it means the baudrate doesn't match. Both devices have to send the same amount of bits per seconds in order to communicate with each other.

This is the Arduino example to test 2 serial lines (for Arduino Mega) at the same time: http://arduino.cc/en/Tutorial/MultiSerialMega


i think the RFID is a other baud rate e.g 115200.. i dont know the device, i dont know if this is the problem, but test it :)

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