Hi,
I'm using a motor shield to run two stepper motors with my Arduino Mega. I also want to use an RFID reader. I've plugged everything in but I had to change two pins because SS (pin 5) and RESET (pin 53) are already being used by the motor shield. I changed the pins in the code to reflect the change I made but it doesn't seem to do anything. The code runs to a point, in my loop function I have this:
// Look for new cards, and select one if present
if ( ! mfrc522.PICC_IsNewCardPresent() || ! mfrc522.PICC_ReadCardSerial() ) {
Serial.println("Select new card");
delay(50);
return;
}
In the console it shows "Select new card" continually. That's all my code does.
Is this a problem with not using the pins as per the documentation or a code issue? My code is an Elegoo example and I've only modified the pin numbers.
Any thoughts?
Thank you 
My stepper motor shield:
My RFID board:
Here's my complete RFID code:
//www.elegoo.com
//2016.12.09
/*
* --------------------------------------------------------------------------------------------------------------------
* Example to change UID of changeable MIFARE card.
* --------------------------------------------------------------------------------------------------------------------
* This is a MFRC522 library example; for further details and other examples see: https://github.com/miguelbalboa/rfid
*
* This sample shows how to set the UID on a UID changeable MIFARE card.
* NOTE: for more informations read the README.rst
*
* @author Tom Clement
* @license Released into the public domain.
*
* Typical pin layout used:
* -----------------------------------------------------------------------------------------
* MFRC522 Arduino Arduino Arduino Arduino Arduino
* Reader/PCD Uno 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 39 // Configurable, see typical pin layout above
#define SS_PIN 31 // Configurable, see typical pin layout above
MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance
/* Set your new UID here! */
#define NEW_UID {0xDE, 0xAD, 0xBE, 0xEF}
MFRC522::MIFARE_Key key;
void setup() {
Serial.println("Setup");
Serial.begin(9600); // Initialize serial communications with the PC
Serial.println("1");
while (!Serial); // Do nothing if no serial port is opened (added for Arduinos based on ATMEGA32U4)
Serial.println("2");
SPI.begin(); // Init SPI bus
Serial.println("3");
mfrc522.PCD_Init(); // Init MFRC522 card
Serial.println("4");
Serial.println(F("Warning: this example overwrites the UID of your UID changeable card, use with care!"));
// Prepare key - all keys are set to FFFFFFFFFFFFh at chip delivery from the factory.
for (byte i = 0; i < 6; i++) {
key.keyByte[i] = 0xFF;
}
}
// Setting the UID can be as simple as this:
//void loop() {
// byte newUid[] = NEW_UID;
// if ( mfrc522.MIFARE_SetUid(newUid, (byte)4, true) ) {
// Serial.println("Wrote new UID to card.");
// }
// delay(1000);
//}
// But of course this is a more proper approach
void loop() {
// Look for new cards, and select one if present
if ( ! mfrc522.PICC_IsNewCardPresent() || ! mfrc522.PICC_ReadCardSerial() ) {
//Serial.println("Select new card");
delay(50);
return;
}
// Now a card is selected. The UID and SAK is in mfrc522.uid.
// Dump UID
Serial.print(F("Card UID:"));
for (byte i = 0; i < mfrc522.uid.size; i++) {
Serial.print(mfrc522.uid.uidByte[i] < 0x10 ? " 0" : " ");
Serial.print(mfrc522.uid.uidByte[i], HEX);
}
Serial.println();
// Dump PICC type
// MFRC522::PICC_Type piccType = mfrc522.PICC_GetType(mfrc522.uid.sak);
// Serial.print(F("PICC type: "));
// Serial.print(mfrc522.PICC_GetTypeName(piccType));
// Serial.print(F(" (SAK "));
// Serial.print(mfrc522.uid.sak);
// Serial.print(")\r\n");
// if ( piccType != MFRC522::PICC_TYPE_MIFARE_MINI
// && piccType != MFRC522::PICC_TYPE_MIFARE_1K
// && piccType != MFRC522::PICC_TYPE_MIFARE_4K) {
// Serial.println(F("This sample only works with MIFARE Classic cards."));
// return;
// }
// Set new UID
byte newUid[] = NEW_UID;
if ( mfrc522.MIFARE_SetUid(newUid, (byte)4, true) ) {
Serial.println(F("Wrote new UID to card."));
}
// Halt PICC and re-select it so DumpToSerial doesn't get confused
mfrc522.PICC_HaltA();
if ( ! mfrc522.PICC_IsNewCardPresent() || ! mfrc522.PICC_ReadCardSerial() ) {
return;
}
// Dump the new memory contents
Serial.println(F("New UID and contents:"));
mfrc522.PICC_DumpToSerial(&(mfrc522.uid));
delay(2000);
}
