i2c read

Good.
I hereby ask for help I am developing a project with an Arduino + expander PCF8574 ... wanted to read the data from the output port of the expander and I am not getting ..
I have this code..

/*
Test program for PCF8574 I2C I/O expander

  • Blinks all ports low then high.
    by Ford
    */

#include "Wire.h"
#define expander B0100000 // Address with three address pins grounded.
// Note that the R/W bit is not part of this address.

void setup() {
Wire.begin();
Serial.begin(9600);

}

void loop() {
Serial.println("LED OFF");
expanderWrite(B00000000);
Serial.print("Read: ");
Serial.println(expanderRead(), BIN);
delay(1000);
Serial.println("LED ON");
expanderWrite(B00100000);
Serial.print("Read: ");
Serial.println(expanderRead(), BIN);
delay(1000);
}

void expanderWrite(byte _data ) {
Wire.beginTransmission(expander);
Wire.send(_data);
Wire.endTransmission();
}

byte expanderRead() {
byte _data;
Wire.requestFrom(expander, 1);
if(Wire.available()) {
_data = Wire.receive();
}
return _data;
}
thanks for attention

SOmewhere on this page - Gammon Forum : Electronics : Microprocessors : I2C - Two-Wire Peripheral Interface - for Arduino - is an I2C sniffer that can see if you use the right address,
and a lot more information about I2C..

Rob

My big problem is that the plot is only 7 bits when writing to the PCF8574 there is no problem seems to read but when is the last bit is one and not know how it goes