Hi,
I got 5 MFRC55 (RFID) reader. When I hook them up together I get a lot of noise on the line. Sometimes it works and sometimes it doesn't.
So it's suggested to use multiplexing on the line. I quote:
"The solution is to use multiplexers for each arduino pin: SCK, MOSI, MISO, then bring every card's SDA pin to GND so they are all selected. Then you initiate just one class object, and start it for each card in turn. That way you can have as many RFID readers in communication as you want, limited only by the multiplexers. "
So I tried that.
I attached a CD4051 Multiplexer on one line. In this case the SCK line and tried to attach 1 reader. It failt. The Arduino does not see the RFID reader. So I am a bit stuck here.
- I connected the SCK line to port 0 on the CD4051.
- If I replace the RFID line on the multiplexer with a LED, the LED works fine. So the multiplexer is connected in the way it should be.
- I can get the RFID to work connected directly to the Arduino.
I feel like i'm close to getting it to work, but I am a bit stuck on what to try next.
/*
* --------------------------------------------------------------------------------------------------------------------
* Example sketch/program showing how to read data from a PICC to serial.
* --------------------------------------------------------------------------------------------------------------------
* This is a MFRC522 library example; for further details and other examples see: https://github.com/miguelbalboa/rfid
*
* Example sketch/program showing how to read data from a PICC (that is: a RFID Tag or Card) using a MFRC522 based RFID
* Reader on the Arduino SPI interface.
*
* When the Arduino and the MFRC522 module are connected (see the pin layout below), load this sketch into Arduino IDE
* then verify/compile and upload it. To see the output: use Tools, Serial Monitor of the IDE (hit Ctrl+Shft+M). When
* you present a PICC (that is: a RFID Tag or Card) at reading distance of the MFRC522 Reader/PCD, the serial output
* will show the ID/UID, type and any data blocks it can read. Note: you may see "Timeout in communication" messages
* when removing the PICC from reading distance too early.
*
* If your reader supports it, this sketch/program will read all the PICCs presented (that is: multiple tag reading).
* So if you stack two or more PICCs on top of each other and present them to the reader, it will first output all
* details of the first and then the next PICC. Note that this may take some time as all data blocks are dumped, so
* keep the PICCs at reading distance until complete.
*
* @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 53 // Configurable, see typical pin layout above
int addressA = 1;
int addressB = 2;
int addressC = 3;
int A = 0; //Address pin A
int B = 0; //Address pin B
int C = 0; //Address pin C
MFRC522 mfrc522(SS_PIN, RST_PIN); // Create MFRC522 instance
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)
pinMode(addressA, OUTPUT);
pinMode(addressB, OUTPUT);
pinMode(addressC, OUTPUT);
multiplex();
SPI.begin(); // Init SPI bus
mfrc522.PCD_Init(); // Init MFRC522
mfrc522.PCD_DumpVersionToSerial(); // Show details of PCD - MFRC522 Card Reader details
Serial.println(F("Scan PICC to see UID, SAK, type, and data blocks..."));
}
void loop() {
multiplex();
// Look for new cards
if ( ! mfrc522.PICC_IsNewCardPresent()) {
return;
}
// Select one of the cards
if ( ! mfrc522.PICC_ReadCardSerial()) {
return;
}
// Dump debug info about the card; PICC_HaltA() is automatically called
mfrc522.PICC_DumpToSerial(&(mfrc522.uid));
}
void multiplex()
{
A = bitRead(0,0); //Take first bit from binary value of i channel.
B = bitRead(0,1); //Take second bit from binary value of i channel.
C = bitRead(0,2); //Take third bit from value of i channel.
//Write address to mux
digitalWrite(addressA, A);
digitalWrite(addressB, B);
digitalWrite(addressC, C);
//digitalWrite(outputpin2, 1);
}
