How to enable 2 IIC buses at the same time?

Code:
/*

  Made by KinCony IoT: https://www.kincony.com



  KC868-A128

  DI1 -> DO1

  DI2 -> DO2

  ...

  DI128 -> DO128



  IIC Bus-A for relay DO:

  SDA = GPIO5

  SCL = GPIO16



  IIC Bus-B for DI:

  SDA = GPIO15

  SCL = GPIO4

*/



#include <Arduino.h>

#include <Wire.h>



#define DO_SDA 5

#define DO_SCL 16



#define DI_SDA 15

#define DI_SCL 4



// PCF8575 address order

uint8_t pcfAddr[8] = {

  0x24, 0x25, 0x21, 0x22,

  0x26, 0x27, 0x20, 0x23

};



// relay output state

// PCF8575: 1 = OFF, 0 = ON

uint16_t relayState[8];



uint16_t readPCF8575(TwoWire &wireBus, uint8_t addr) {

  wireBus.requestFrom(addr, (uint8_t)2);



  if (wireBus.available() < 2) {

    return 0xFFFF;

  }



  uint8_t lowByte = wireBus.read();

  uint8_t highByte = wireBus.read();



  return ((uint16_t)highByte << 8) | lowByte;

}



void writePCF8575(TwoWire &wireBus, uint8_t addr, uint16_t value) {

  wireBus.beginTransmission(addr);

  wireBus.write(value & 0xFF);

  wireBus.write((value >> 8) & 0xFF);

  wireBus.endTransmission();

}



void setup() {

  Serial.begin(115200);

  delay(1000);



  Wire.begin(DO_SDA, DO_SCL);      // IIC Bus-A, relay

  Wire1.begin(DI_SDA, DI_SCL);     // IIC Bus-B, digital input



  // Init all relays OFF

  for (int i = 0; i < 8; i++) {

    relayState[i] = 0xFFFF;

    writePCF8575(Wire, pcfAddr[i], relayState[i]);

  }



  Serial.println("KC868-A128 DI trigger DO ready.");

}



void loop() {

  for (int board = 0; board < 8; board++) {

    uint16_t inputState = readPCF8575(Wire1, pcfAddr[board]);



    // DI low active

    // DI = 0 -> relay ON

    // DI = 1 -> relay OFF

    relayState[board] = inputState;



    writePCF8575(Wire, pcfAddr[board], relayState[board]);

  }



  delay(50);

}