PCF8574P Port Expander and Teensy 3.2

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dimitre

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I'm trying to use the PCF8574P port expander with Teensy 3.2 but I can't receive the transmission yet.
I'm posting the wiring and the code.
interrupt seems to be working, but no transmission yet.

If I use pullup resistors in i2c ports the interrupt stops working.
I've tried different chips, different teensies and checked continuity for all connections.

Tried a i2c port scanner too and it doesn't find i2c device in any address.

Ideas are very welcome

IMG_4917.jpg
PCF8574P.png

Code:
//PCF8574P

#include <Wire.h>
//Thanks for your help, my IC is a PCF8574AF, so the correct address was 0x38 (decimal 56)
//B00100000 //B00111000
#define EXPANDER 0x20  //expander address

void setup() {
  Serial.begin(9600);
  Wire.begin();
  delay(300);
  expanderWrite(B11111111);
  attachInterrupt(5, expanderInterrupt, CHANGE);
  Serial.println("begin ");
  Serial.println(EXPANDER);
}

void loop() {
  Wire.requestFrom(EXPANDER, 1);
  if (Wire.available()) {
    byte _data = Wire.read();
    Serial.print("DATA :: ");
    Serial.println(_data, BIN);

    Serial.println(_data, BIN);
    Serial.println(_data);
    byte inpBuff = _data & 0x01;
    Serial.println(inpBuff, HEX);
  }
}

void expanderInterrupt() {
  Serial.print("interrupt :: ");

  Wire.requestFrom(EXPANDER, 1);
  if (Wire.available()) {
    byte _data = 0;
    _data = Wire.read();
    Serial.print("DATA :: ");
    Serial.println(_data, BIN);

    Serial.println(_data, BIN);
    Serial.println(_data);
    byte inpBuff = _data & 0x01;
    Serial.println(inpBuff, HEX);
  }
  Serial.println("------------------------");
}

void expanderWrite(byte _data ) {
  Wire.beginTransmission(EXPANDER);
  Wire.write(_data);
  Wire.endTransmission();
}

//byte expanderRead() {
//  byte _data = 0;
//  Wire.requestFrom(EXPANDER, 1);
//  if (Wire.available()) {
//    _data = Wire.read();
//    Serial.println(_data, BIN);
//  }
//  return _data;
//}


and scanner code

Code:
// --------------------------------------
// i2c_scanner
//
// Version 1
//    This program (or code that looks like it)
//    can be found in many places.
//    For example on the Arduino.cc forum.
//    The original author is not known.
// Version 2, Juni 2012, Using Arduino 1.0.1
//     Adapted to be as simple as possible by Arduino.cc user Krodal
// Version 3, Feb 26  2013
//    V3 by louarnold
// Version 4, March 3, 2013, Using Arduino 1.0.3
//    by Arduino.cc user Krodal.
//    Changes by louarnold removed.
//    Scanning addresses changed from 0...127 to 1...119,
//    according to the i2c scanner by Nick Gammon
//    http://www.gammon.com.au/forum/?id=10896
// Version 5, March 28, 2013
//    As version 4, but address scans now to 127.
//    A sensor seems to use address 120.
// 
//
// This sketch tests the standard 7-bit addresses
// Devices with higher bit address might not be seen properly.
//

#include <Wire.h>


void setup()
{
  Wire.begin();

  Serial.begin(9600);
  Serial.println("\nI2C Scanner");
}


void loop()
{
  byte error, address;
  int nDevices;

  Serial.println("Scanning...");

  nDevices = 0;
  for(address = 1; address < 127; address++ ) 
  {
    // The i2c_scanner uses the return value of
    // the Write.endTransmisstion to see if
    // a device did acknowledge to the address.
    Wire.beginTransmission(address);
    error = Wire.endTransmission();

    if (error == 0)
    {
      Serial.print("I2C device found at address 0x");
      if (address<16) 
        Serial.print("0");
      Serial.print(address,HEX);
      Serial.println("  !");

      nDevices++;
    }
    else if (error==4) 
    {
      Serial.print("Unknow error at address 0x");
      if (address<16) 
        Serial.print("0");
      Serial.println(address,HEX);
    }    
  }
  if (nDevices == 0)
    Serial.println("No I2C devices found\n");
  else
    Serial.println("done\n");

  delay(5000);           // wait 5 seconds for next scan
}
 
Thanks @tonton81.
I've updated with some pullups and data is transmitting but interrupt pin stopped working. should I do something in that pin too?
I've changed IC VCC to 3.3v now so I use pullups on the protoboard.
pullups.jpg

which range of resistors should I use for i2c pullup?
 
@dimitre
The PCF8574 INT pin is open drain, so it also needs a pullup resistor. Any value between 4k7 & 10k should do it.
 
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