MFRC522 code will not work in one project, but does in another

hello,
currently using mfrc522 component connect smartsystem developing. have shortened code as possible , looks this:

code: [select]

#include <spi.h>
#include <mfrc522.h>
#define ss_pin 53
#define rst_pin 5

mfrc522 mfrc522(ss_pin, rst_pin);        // create mfrc522 instance.

void setup() {
        serial.begin(9600);        // initialize serial communications pc
        spi.begin();               // init spi bus
        mfrc522.pcd_init();        // init mfrc522 card
}

void loop() {
 
        // new cards, , select 1 if present
        if ( ! mfrc522.picc_isnewcardpresent() || ! mfrc522.picc_readcardserial() ) {
            delay(50);
            return;
        }
       
        // dump uid
        serial.print(f("card uid:"));
        (byte = 0; < mfrc522.uid.size; i++) {
                serial.print(mfrc522.uid.uidbyte[i] < 0x10 ? " 0" : " ");
                serial.print(mfrc522.uid.uidbyte[i], dec);
        }
        serial.println();

}

this code works when use in new project. reads , prints uid of card. problem when "copy paste" other project, stops working after 1 use. can read 1 card, doesn't work anymore. project has keypad system. keypad system works letting first create code, using code unlock , lock unit. want do, user have option of using rfid-card unlock/lock (which easy enough), normal keypad. code troubling me below:

code: [select]

#include <keypad.h>

#include <spi.h>
#include <mfrc522.h>

//set-up mfrc-chippen
#define ss_pin 53
#define rst_pin 5

mfrc522 mfrc522(ss_pin, rst_pin);

const byte numrows = 4;
const byte numcols = 4;

char keymap[numrows][numcols]=
{
 {'1', '2', '3', 'a'},
 {'4', '5', '6', 'b'},
 {'7', '8', '9', 'c'},
 {'*', '0', '#', 'd'}
};

//code shows the keypad connections arduino terminals
byte rowpins[numrows] = {9,8,7,6}; //rows 0 3
byte colpins[numcols]= {5,4,3,2}; //columns 0 3

//initializes instance of keypad class
keypad mykeypad= keypad(makekeymap(keymap), rowpins, colpins, numrows, numcols);


void setup() {
  serial.begin(9600);
  spi.begin();               // init spi bus
  mfrc522.pcd_init();        // init mfrc522 card
}

void loop() {

 // new cards, , select 1 if present

  if ( mfrc522.picc_isnewcardpresent() ||  mfrc522.picc_readcardserial() ) {
       serial.print(f("card uid:"));
       for (byte = 0; < mfrc522.uid.size; i++) {
               serial.print(mfrc522.uid.uidbyte[i] < 0x10 ? " 0" : " ");
               serial.print(mfrc522.uid.uidbyte[i], hex);
       }
       serial.println();

       }
 
 char keypressed = mykeypad.getkey();
 static string passwordchosen = "";
 static string keycodegiven = "";
 static bool passsetup = false;
 static bool alarmuser = false;
 string chipuid = "bla bla";
 
 if(!passsetup){
   if(keypressed == '#'){
     serial.print("chosen:" + passwordchosen);
     passsetup = true;
   }
   else if(keypressed == '*'){
     passwordchosen = "";
     serial.print("reset pw");
   }
       else if(keypressed == 'a'){
     // nothing
   }
   else if(keypressed == 'b'){
     // nothing
   }
       else if(keypressed == 'c'){
     // nothing
   }
   else if(keypressed == 'd'){
     // nothing
   }
   else if (keypressed != no_key){
     passwordchosen += string(keypressed);
     serial.print("pw:" + passwordchosen);
   }
   
 }
 else if (passsetup){
   if(keypressed == 'a'){
     serial.println("next page");
     serial.println(keycodegiven);
   }
   else if(keypressed == 'b'){
     serial.println("previous page");
     serial.println(keycodegiven);
   }
   else if(keypressed == 'c'){
     // nothing
   }
   else if(keypressed == 'd'){
     // nothing
   }
   else if(keypressed == '*')
   {
     serial.println("reset");
     keycodegiven = "";
     serial.println(keycodegiven);
   }
   else if(keypressed == '#')
   {
     serial.println("enter");
       if(keycodegiven == passwordchosen && alarmuser == false){
        serial.println("correct pw, may pass!");
        alarmuser = true;
        keycodegiven = "";
       }
       else if(keycodegiven == passwordchosen && alarmuser == true){
        serial.println("correct pw, locked!");
        alarmuser = false;
        keycodegiven = "";
       }
       else{
         serial.println("error, wrong password!");
         keycodegiven = "";
       }
   }
   else if (keypressed != no_key)
   {
     serial.println(keypressed);
     keycodegiven += string(keypressed);
     serial.println(keycodegiven);
   }
 }
}

i using arduino mega, , keypad not connected it.

you're using pin 5 both rst_pin , 1 of keypad pins... don't that.

also, using pin 50-something chip select? mega you're using, right? (if not, pin doesn't exist - compiler not able warn in case, either.)

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