UHF-RFID JRD-4032 – Short Reading Distance Issue

[IotHobbyist]

Dear M5Stack Community,

I recently purchased the JRD-4032 UHF-RFID modules from M5stack store and am currently using one in a project based on a standard ESP32 (Arduino IDE) together with your official UHF-RFID library.

At the moment, I am experiencing significantly lower reading distances than specified in your documentation. I would greatly appreciate your support in resolving this issue, as I am working under time constraints due to project deadlines.

Current Setup:

• Controller: Standard ESP32
• RFID Module: JRD-4032 UHF-RFID
• Development Environment: Arduino IDE
• Library: Official M5Stack UHF-RFID library
• Main functions used:
  • EPC scanning (pollingOnce and pollingMultiple)
  • Memory read (readCard)
  • Memory write (writeCard)
  • (and of course other initializing functions and the select function for the readCard and writeCard)

Observed Reading Distance:

• With included M5Stack UHF tags: approx. 40 cm maximum
• With third-party Class Gen1 tags (860–960 MHz): approx. 50 cm maximum (Link: https://www.amazon.de/-/en/860-960MHz-Warehouse-Parking-Logistics-Applications/dp/B07H94DGC2?th=1)

This is considerably below the 1.5–2 m stable range stated in the documentation.

Troubleshooting Steps Taken:

1. Transmit Power

   I verified in both the documentation and the library source code that the transmit power is set to maximum in my implementation.

2. Frequency Consideration

   I understand from your FAQ that the antenna frequency is fixed at 922 MHz. Since I am currently only testing and have not modified the frequency in software, both hardware and software should still be operating at 922 MHz.

3. Power Supply Investigation

   • Initial setup: RFID module powered directly from the ESP32 (3.3V).

     → Reading distance: approx. 30 cm or less

   • Second setup: External stable power supply (separate regulated source). (Circuit schema below)

     → Reading distance improved to 40–50 cm

This suggests that insufficient current may have been affecting performance initially. However, even with a dedicated external power source, the reading distance remains far below the expected range.

Could you please advise:

• What current and voltage specifications are required for optimal performance?
• Whether additional hardware adjustments (e.g., antenna matching, grounding considerations) are necessary?
• If there are recommended configuration settings for EU operation that may improve range?

Additionally, I would like to clarify:

Does the achievable reading distance differ depending on the function used?

• EPC scan only (pollingOnce / pollingMultiple)
• Reading user memory (readCard)
• Writing user memory (writeCard)

#include <Arduino.h>
#include "UNIT_UHF_RFID.h"

Unit_UHF_RFID uhf;
String info = "";

// UART pins for ESP32
#define RFID_TX_PIN 16
#define RFID_RX_PIN 17

void setup() {
    // USB Serial Monitor
    Serial.begin(115200);
    delay(1000);
    Serial.println("ESP32 UHF RFID starting...");

    // Start RFID module
    uhf.begin(&Serial2, 115200, RFID_TX_PIN, RFID_RX_PIN, false);

    // Check module version
    while (true) {
        info = uhf.getVersion();
        if (info != "ERROR") {
            Serial.print("RFID Version: ");
            Serial.println(info);
            break;
        }
        Serial.println("Waiting for RFID module...");
        delay(500);
    }

    // Set TX power
    uhf.setTxPower(2600);
    Serial.println("RFID initialized successfully");
}

uint8_t write_buffer[] = {0xab, 0xcd, 0xef, 0xdd};
uint8_t read_buffer[4] = {0};

void loop() {
    Serial.println("\nPolling once...");
    uint8_t result = uhf.pollingMultiple(100);
    Serial.print("Scan result: ");
    Serial.println(result);

    if (result > 0) {
        for (uint8_t i = 0; i < result; i++) {
            Serial.print("PC: ");
            Serial.println(uhf.cards[i].pc_str);

            Serial.print("RSSI: ");
            Serial.println(uhf.cards[i].rssi_str);

            Serial.print("EPC: ");
            Serial.println(uhf.cards[i].epc_str);

            Serial.println("----------------------");
        }

        // Select first card
        Serial.println("Selecting first tag...");
        if (uhf.select(uhf.cards[0].epc)) {
            Serial.println("Select OK");
        } else {
            Serial.println("Select ERROR");
        }

        Serial.print("Selected EPC: ");
        Serial.println(uhf.selectInfo());

        // Write data
        Serial.println("Writing data...");
        if (uhf.writeCard(write_buffer, sizeof(write_buffer), 0x04, 0, 0x00000000)) {
            Serial.println("Write OK");
        } else {
            Serial.println("Write ERROR");
        }

        // Read data
        Serial.println("Reading data...");
        if (uhf.readCard(read_buffer, sizeof(read_buffer), 0x04, 0, 0x00000000)) {
            Serial.println("Read OK");
            Serial.print("Data: ");
            for (uint8_t i = 0; i < sizeof(read_buffer); i++) {
                Serial.printf("%02X ", read_buffer[i]);
            }
            Serial.println();
        } else {
            Serial.println("Read ERROR");
        }
    }

    delay(100);
}

I am using this library:
https://github.com/m5stack/M5Unit-UHF-RFID/tree/master