I have an RDM6300 connected to an Arduino Mega and code that can read the tag just fine:

// Function prototypes
void setup(void);
void loop(void);

// RDM6300 packet details
#define RDM6300_PACKET_SIZE  14
#define RDM6300_PACKET_BEGIN 0x02
#define RDM6300_PACKET_END   0x03

// Globack for reading RFID data
char buff[RDM6300_PACKET_SIZE];
uint32_t tag_id;
uint8_t checksum;

void setup(void) {
  Serial.println("Setting up...");

  // RFID board setup

  Serial.println("READY. Scanning tags...");

void loop(void) {
  while (Serial1.available() > 0) {
    if (Serial1.peek() == RDM6300_PACKET_BEGIN || Serial1.read()) {
      Serial1.readBytes(buff, RDM6300_PACKET_SIZE);
      if (buff[13] != RDM6300_PACKET_END) {
      else {
        buff[13] = 0;
        checksum = strtol(buff + 11, NULL, 16);
        buff[11] = 0;
        tag_id = strtol(buff + 3, NULL, 16);
        buff[3] = 0;
        checksum ^= strtol(buff + 1, NULL, 16);
        for (uint8_t i = 0; i < 32; i += 8) checksum ^= ((tag_id >> i) & 0xFF);
        if (checksum) {
        else {
    else {
      Serial.println(Serial1.peek(), HEX);

However, the output stops after reading the tag around 28 times sometimes (more, sometimes less...) . If I remove the tag from the "read" area and put it back on it start reading again for a number of times and then stop.

I have an LED connect to the RDM6300 board that is supposed to show when it detects a tag and it does blink while I hold the tag over the antenna but also stops when the Arduino stops receiving data.

As the RDM6300 is supposed to be a continuous RFID reader I was expecting to receive data for the duration I kept the tag over the antenna.

Anyone faced this same thing and found a solution ?

Thanks for any hints.

  • only guessing here ...... that may be normal behavior for RFID tags ..... maybe repeated reads drain the power from the tag faster than it can be refilled ..... what happens if you introduce a 1 second delay between scans?? – jsotola Apr 30 '19 at 4:01
  • @jsotola Unfortunately there is no "read" trigger. The module (seeedstudio.com/125Khz-RFID-module-UART.html) just starts spitting out data as soon as a tag is within reading distance of the antenna. – Andre Courchesne Apr 30 '19 at 11:57

Ok, so it seems to be related to the tags. The "standard" keychain and credit-card type cards when used with the RDM360 only emit a single time their ID.

The same tags when used with the RDM3600 module will emit their tags a few times, but at some point the antenna can not provide enough power for the tag to emit again and the flow stops.

Fortunatly the tags I use for this project are very small tags made for birds (https://eccel.co.uk/product/3-3mm-em4102-pit-bird-tag-grey/) and when used with the RDM360 will continuoisly retransmit. I guess they need less power and the antenna is able to provide enough.

If you want to use continuous reading using regular tags, I believe there is still a way... If you "reset" the RDM360 or RDM3600 it forces "re-energize" of the tag and transmission resumes. So one could use a simple transistor to switch on and off the power to the RFID module using an Arduino I/O.

  • It's OK to accept your own answer as the solution to the problem. I think you get 15 rep for it. – VE7JRO Oct 30 '19 at 0:27

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