I2C PCF8574 READ

[esa]

Hello,
I have a question about the code posted in the code forum about reading a PCF8574.
The code is ( a little simplified ) :
int IN8574(int device_addr)
{
int io_field;
i2c_write(0x40 | device_addr<<1 | I2CREAD);
io_field=i2c_read(); /* this byte contains the prior conversion result. */
io_field=i2c_read(0); /* returned data is big-endian (msbit first) */
i2c_stop();
return(io_field);
}
But, I alway have 255 for io_field.

So, I use my old code :

byte IN(byte adr)
{
byte datain;
I2C_start();
I2C_write((adr<<1)|0x41);
datain=I2C_read();
I2C_write((adr<<1)|0x41);
I2C_write(0xff);
I2C_stop();
return(datain);
}
And it is working.

Can someone help me to understand where is the problem ?
I use PIC16F877
#use i2c(MASTER, SDA=PIN_C4, SCL=PIN_C3,SLOW)

[PCM programmer]

[Guest]

It's working now
Thanks for the quick answer