Using MFRC522 RFID Reader With ATTINY84

[cherkens]

I am having trouble using the MFRC522 RFID reader with the attiny84. I am trying to make a keycard security for a truck anti-theft system. I can make an atmega8 microcontroller work very well very easily, however I do not want to "waste" one if I don't need to. I am a complete noob, so this may be super easy for you guys to figure out. So far I have MOSI to pin6, MISO to pin5, SCK to pin4, SDA to pin10, RESET to pin8, GND to GND, 3.3v to 3.3v. I have absolutely no resistors, capacitors or anything(and this may be the problem). I am using ATTinyCore and the code seems to upload to the attiny84 chip without problems. I know the RFID reader works and the ID number for the card is correct. Here is the code:

#include <SPI.h>
#include <RFID.h>
#define SS_PIN 10
#define RST_PIN 8
RFID rfid(SS_PIN, RST_PIN);
String rfidCard;
int i;
int relay = 3;
int led = 9;

void setup() {
  SPI.begin();
  rfid.init();
  pinMode(relay, OUTPUT);
  digitalWrite(relay, LOW);
 pinMode(led, OUTPUT);
 digitalWrite(led, HIGH);
}

void loop() {


  if (rfid.isCard()) {
    if (rfid.readCardSerial()) {
      rfidCard = String(rfid.serNum[0]) + " " + String(rfid.serNum[1]) + " " + String(rfid.serNum[2]) + " " + String(rfid.serNum[3]);
      
    
if (rfidCard=="211 160 177 30"){  
  digitalWrite(relay, HIGH);
  
}else if(rfidCard=="243 207 206 46"){
  digitalWrite(relay, HIGH);

}else if(rfidCard=="17 145 161 38"){
  digitalWrite(relay, HIGH);


}else{
  
    
} 

  
}
}

rfid.halt();
}

This exact code works perfectly fine with the atmega8 chip.
Here are the settings I have selected:

Any help is appreciated. Thanks

[FernandoGarcia]

Look for this:

Attiny84 / RFID

You're using the stock SPI library on a chip without hardware SPI - unsurprisingly, all the registers associated with the SPI hardware don't exist. There is a USI, which can be used to do SPI, with a different library - but since the library for the RFID reader includes SPI as well, you have to modify that. This is a pain in the ass, so I don't recommend this approach. There is a better way: Instead of whatever core you're using, use my core (board manager URL in my sig, or see ATTinyCore/Inst…

[cherkens]

I have already read that and am using the attinycore. Unless I am thinking wrong, all I need to do is copy the attinycore url, put it in the preferences url section, and use it in the toolbar right?

[FernandoGarcia]

Yes, just make sure to use latest stable version V1.0.4.

Did you some test with ATTiny Core and a SPI device?

[cherkens]

The only SPI device I have is the RFID card reader. I don't have another SPI device to test with.