I have successfully built this circuit.

I now have 16 outputs. 16bit

How do I get 32 outputs. 32bit

Or 64 bits.

Apparently you can link up to 5 of these.

I have tried connecting 2 of these by linking pin1, with no luck.

Thanks in advance.

You need to tie the SDA and SCL lines to each PCF8575C and then set up unique address on each (A0, A1 & A2). You only need to tie pin 1, interrupt, to each if you are using that feature.

You should be able to link up to 8 of them to one I2C interface.

to achive a possable 8 ofthese devics,the address pins meedto beat different logic levels,

A0 A1 A2

chip1 0 0 0

chip2 1 0 0

chip3 0 1 0

.. ..

chip5 1 0 1

chip6 0 1 1

chip7 1 1 1

hope this makes sens :)

Ceri

Also you need to set the appropriate address in the i2c routines call. For your first device hardware address is 32 (dec)(A2=A1=A0=0) 0 1 0 0 A2 A1 A0 - format of slave address

Thank you for all your help.

I understand the bit about tying the address lines. (Do I need to add more pull up resistors?)

I don't really understand how to set up a unique address for each chip. Are you referring to pin A0?

I am trying to control lamps and buttons on a pinball machine. I would like to do the following:

Using 4 PCF8575s I would like to use

1 PCF for 16 inputs. 3 PCFs for 3 x 16 outputs.

I used the code below successfully with 1 PCF8575

How do I modify the below code to work with 4 PCF8575s?

#include "mbed.h"
#include "PCF8575.h"

PCF8575 IO(p9, p10, 0x40);  // sda, scl, address
int var;

byte a;
                    // integer variable

int main() {
       while(1){
        IO.write(0xFFFF);   // All outputs goes high. 
        wait(1);
        IO.write(0x0000);   // All outputs go low
        wait(1);
        var = IO.read();    // Read the inputs on the PCF8575 to integer. 
}
}

Cheers David

To set address for each chip, to pullup or pulldown the A0-A2 accordingly. In your schematic, the chip is set to address 0 as you tied all A0-2 to ground. Pullup on A1 on the second chip get will get you address 1 for it.