Frequently Asked Question

1. Important Notes

• start / offset unit is Word (2 Bytes): When modifying the PC value, you MUST set this parameter to 1. Passing an incorrect value will overwrite the CRC or the EPC data body.
• epc parameter is used to "target/locate the tag": Passing an incorrect EPC value will result in a "Tag Not Found" error.
• Modifying PC does NOT automatically clear/pad EPC data: After extending the declared length, the reader will read residual data following the tag memory. If full rewriting is required, separately write data starting at offset = 2.

2. Parameter Comparison Table

3. API V1 vs V2 Core Method Comparison

4. API V1 Complete Method & Example

Method Signature

public DeviceResponse RFIDDirectWriteTagByEPC(
    byte[] password, 
    byte[] epc, 
    RFIDMemoryBank bank, 
    int start, 
    int retry, 
    byte[] data
);

Example Code (Setting PC Length to 96-bit)

// 1. Prepare parameters
byte[] password = new byte[4];                        // 4 zero-bytes for unlocked tag
byte[] currentEpc = hexToBytes("300833B21111222233334444"); // Target tag's actual current EPC (for targeting)
RFIDMemoryBank bank = RFIDMemoryBank.EPC;             // Specify EPC Bank (Fixed value)
int start = 1;                                        // Word Offset = 1 (Points to PC address)
int retry = 3;                                        // Retry 3 times
byte[] pcData = new byte[] {(byte)0x30, (byte)0x00};  // New PC value (0x3000 = 96-bit length)

// 2. Execute write
DeviceResponse response = mRfidManager.RFIDDirectWriteTagByEPC(
    password,
    currentEpc,
    bank,
    start,
    retry,
    pcData
);

// 3. Handle response
if (response == DeviceResponse.OperationSuccess) {
    Log.i("RFID", "V1 Write PC Successful!");
} else {
    String errorMsg = mRfidManager.GetLastError();
    Log.e("RFID", "V1 Write Failed, Reason: " + errorMsg);
}

5. API V2 Complete Method & Example

Method Signature

public int rfidDirectWriteTagByEPC(
    byte[] password, 
    byte[] epc, 
    RFIDMemoryBank bank, 
    int start, 
    int retry, 
    byte[] data, 
    int timeoutMilliseconds
);

Example Code

new Thread(new Runnable() {
    @Override
    public void run() {
        // 1. Prepare parameters
        byte[] password = new byte[4];                        // 4 zero-bytes for unlocked tag
        byte[] currentEpc = hexToBytes("300833B21111222233334444"); // Target tag's actual current EPC
        RFIDMemoryBank bank = RFIDMemoryBank.EPC;             // Specify EPC Bank
        int start = 1;                                        // Word Offset = 1 (Points to PC address)
        int retry = 3;                                        // Retry 3 times
        byte[] pcData = new byte[] {(byte)0x30, (byte)0x00};  // New PC value (0x3000)
        int timeout = 5000;                                   // Timeout set to 5000 ms (5 seconds)

        // 2. Execute write
        int result = mRfidManager2.rfidDirectWriteTagByEPC(
            password,
            currentEpc,
            bank,
            start,
            retry,
            pcData,
            timeout
        );

        // 3. Handle response
        if (result == 0) {
            Log.i("RFID", "V2 Write PC Successful!");
        } else {
            String errorMsg = mRfidManager2.getLastError();
            Log.e("RFID", "V2 Write Failed, Code: " + result + ", Reason: " + errorMsg);
        }
    }
}).start();