MFRCC522 “Is Defect or Unkown”

I am using an RC522 reader with Arduino UNO. This is the library I am using.

But, when I try a firmware check, in the serial I get this error: Firmware version: 0x12, result: defect or unknown

I checked the connections and they were all correct. My RC522 needs 3.3v and it is connected to the 3.3v pin of my Arduino board. Also, all the pins are soldered.

Here is the code of the firmware check (it came with the library):

 * --------------------------------------------------------------------------------------------------------------------
 * Example sketch/program to test your firmware.
 * --------------------------------------------------------------------------------------------------------------------
 * This is a MFRC522 library example; for further details and other examples see:
 * This example test the firmware of your MFRC522 reader module, only known version can be checked. If the test passed
 * it do not mean that your module is faultless! Some modules have bad or broken antennas or the PICC is broken.
 * @author Rotzbua
 * @license Released into the public domain.
 * Typical pin layout used:
 * -----------------------------------------------------------------------------------------
 *             MFRC522      Arduino       Arduino   Arduino    Arduino          Arduino
 *             Reader/PCD   Uno/101       Mega      Nano v3    Leonardo/Micro   Pro Micro
 * Signal      Pin          Pin           Pin       Pin        Pin              Pin
 * -----------------------------------------------------------------------------------------
 * RST/Reset   RST          9             5         D9         RESET/ICSP-5     RST
 * SPI SS      SDA(SS)      10            53        D10        10               10
 * SPI MOSI    MOSI         11 / ICSP-4   51        D11        ICSP-4           16
 * SPI MISO    MISO         12 / ICSP-1   50        D12        ICSP-1           14
 * SPI SCK     SCK          13 / ICSP-3   52        D13        ICSP-3           15

#include <SPI.h>
#include <MFRC522.h>

#define RST_PIN         9          // Configurable, see typical pin layout above
#define SS_PIN          10         // Configurable, see typical pin layout above

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

 * Check firmware only once at startup
void setup() {
  Serial.begin(9600);   // Initialize serial communications with the PC
  while (!Serial);      // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
  SPI.begin();          // Init SPI bus
  mfrc522.PCD_Init();   // Init MFRC522 module
  Serial.println(F("MFRC522 Digital self test"));
  mfrc522.PCD_DumpVersionToSerial();  // Show version of PCD - MFRC522 Card Reader
  Serial.println(F("Only known versions supported"));
  Serial.println(F("Performing test..."));
  bool result = mfrc522.PCD_PerformSelfTest(); // perform the test
  Serial.print(F("Result: "));
  if (result)
    Serial.println(F("DEFECT or UNKNOWN"));

void loop() {} // nothing to do

The process i followed to install the the library was: Sketch > include library > add .Zip library

The Uno 3.3V output is too weak for an RFID reader. You need a more powerful 3.3V supply for it.

You have problems and those that have it working on the 3v3 pin are lucky. The 3.3V regulated output is able to supply 150mA max, which is the limit of the 3.3V regulator. The MFRC522 can use over 100mA. The CH340 uses that regulator. What else do you have connected? Posting a schematic showing all the power connections will be a big help.

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