How to use multiple PN532 over i2c bus(es) and SPI?

Projects Programming
1

I am working on a project that involves 3 PN532_modules to an ESP32, which sends the Tag_ID over BLE. Plan A was to use One module on i2c_1, second on I2C_2 and third over SPI.

The SPI one works as expected. Though I am having issues with using 2 I2c Buses using the same Adafruit Library. Exact issues are-

  • Unreliable reading while using 2 different i2c buses
  • Sometimes the SPI bus freezes after scanning a Tag on one of i2c connected readers. My code is here

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#include <Arduino.h>

#include <Wire.h>
//#include <Adafruit_PN532_2.h>
#include <Adafruit_PN532.h>


#define SDA_1 (21)
#define SCL_1 (22)  
#define SDA_2   (33)
#define SCL_2   (32)  

Adafruit_PN531 nfc1(SDA_1, SCL_1);
Adafruit_PN532 nfc2(SDA_2, SCL_2);


void setup(void) {
  Serial.begin(115200);
  while (!Serial) delay(10); 
Serial.println("Serial ready");

  nfc1.begin();
  nfc2.begin();

  uint32_t versiondata_1 = nfc1.getFirmwareVersion();
  if (! versiondata_1) {
    while (1); // halt
  }
Serial.println(versiondata_1);

  uint32_t versiondata_2 = nfc2.getFirmwareVersion();
  if (! versiondata_2) {
    while (1); // halt
  }
Serial.println(versiondata_2);
}


void loop(void) {

  uint8_t success_1;
  uint8_t uid_1[] = { 0, 0, 0, 0, 0, 0, 0 };  // Buffer to store the returned UID
  uint8_t uidLength_1;                        // Length of the UID (4 or 7 bytes 

  uint8_t success_2;
  uint8_t uid_2[] = { 0, 0, 0, 0, 0, 0, 0 };  // Buffer to store the returned UID
  uint8_t uidLength_2;                        // Length of the UID (4 or 7 bytes



  success_1 = nfc1.readPassiveTargetID(PN532_MIFARE_ISO14443A, uid_1, &uidLength_1);
  delay(10);
  
  success_2 = nfc2.readPassiveTargetID(PN532_MIFARE_ISO14443A, uid_2, &uidLength_2);
  delay(10);



  if (success_1) 
  {
    Serial.println(success_1);
    Serial.print(" UID_1 Value: ");
    nfc1.PrintHex(uid_1, uidLength_1);
    Serial.println("");
  }
  delay(10);


  if (success_2) 
  {
    Serial.print(" UID_2 Value: ");
    nfc2.PrintHex(uid_2, uidLength_2);
    Serial.println("");
  }
  delay(10);


}
2

It appears to me the easiest is to use SPI for all three, they have a CS that would allow unlimited number of these things connected. That would also have a big impact on the amount of software you will need to drive them.

3

what is 531?

4

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