Hi, I hope it's right forum.
I'm working on building 4x4x4 LED Cube. So far, I managed to build cube which works great when I connect 16 anodes (pins 0-13 and A0,A1) and 4 cathodes (pins A2-A5) to my Arduino UNO board.
But I would like to add to this some buttons for switching between 'patterns'.
I bought expander PCF8574AN where I would like to connect those 4 cathodes (I can't use both I2C and Analog A4,A5 right?). I connected addresses pins to ground (pins 1,2,3) and also Vss (pin 8) to GND on Arduino.
On pins 9-12 I connected my cables from cathodes. I left INT pin empty and connected 14 to SCL and 15 to SDA on Arduino board (above AREF pin).
I think I messed up something with my code or I am missing something but I can't figure out what is it 
Here is my code for cube which doesn't work:
#include <avr/pgmspace.h>
#include <PCF8574.h>
#include <Wire.h>
PCF8574 expander;
//#include <avr/pgmspace.h> // allows use of PROGMEM to store patterns in flash
#define CUBESIZE 4
#define PLANESIZE CUBESIZE*CUBESIZE
#define PLANETIME 3333 // time each plane is displayed in us -> 100 Hz refresh
#define TIMECONST 20 // multiplies DisplayTime to get ms - why not =100?
// LED Pattern Table in PROGMEM - last column is display time in 100ms units
// TODO this could be a lot more compact but not with binary pattern representation
const char PatternTable[] PROGMEM = {
// blink on and off
B0001,B0000,B0000,B0000,B0001,B0000,B0000,B0000,B0000,B0000,B0000,B0000,B0000,B0000,B0000,B0000,10,
//and so on...
};
/*
** Defining pins in array makes it easier to rearrange how cube is wired
** Adjust numbers here until LEDs flash in order - L to R, T to B
** Note that analog inputs 0-5 are also digital outputs 14-19!
** Pin DigitalOut0 (serial RX) and AnalogIn5 are left open for future apps
*/
int LEDPin[] = {0, 1, 2, 3, 4, 5, 6, 7, 8, 9, 10, 11, 12, 13, 14, 15};
int PlanePin[] = {4, 5, 6, 7};
// initialization
void setup()
{
Wire.begin();
Serial.begin(57600);
Serial.println("PCF8575 ok");
int pin; // loop counter
// set up LED pins as output (active HIGH)
for (pin=0; pin<PLANESIZE; pin++) {
pinMode( LEDPin[pin], OUTPUT );
}
expander.begin(0x38);
// set up plane pins as outputs (active LOW)
for (pin=0; pin<CUBESIZE; pin++) {
expander.pinMode( PlanePin[pin], OUTPUT );
expander.pullUp( PlanePin[pin] );
}
}
// display pattern in table until DisplayTime is zero (then repeat)
void loop()
{
// declare variables
byte PatternBuf[PLANESIZE]; // saves current pattern from PatternTable
int PatternIdx;
byte DisplayTime; // time*100ms to display pattern
unsigned long EndTime;
int plane; // loop counter for cube refresh
int patbufidx; // indexes which byte from pattern buffer
int ledrow; // counts LEDs in refresh loop
int ledcol; // counts LEDs in refresh loop
int ledpin; // counts LEDs in refresh loop
// Initialize PatternIdx to beginning of pattern table
PatternIdx = 0;
// loop over entries in pattern table - while DisplayTime>0
do {
// read pattern from PROGMEM and save in array
memcpy_P( PatternBuf, PatternTable+PatternIdx, PLANESIZE );
PatternIdx += PLANESIZE;
// read DisplayTime from PROGMEM and increment index
DisplayTime = pgm_read_byte_near( PatternTable + PatternIdx++ );
// compute EndTime from current time (ms) and DisplayTime
EndTime = millis() + ((unsigned long) DisplayTime) * TIMECONST;
// loop while DisplayTime>0 and current time < EndTime
while ( millis() < EndTime ) {
patbufidx = 0; // reset index counter to beginning of buffer
// loop over planes
for (plane=0; plane<CUBESIZE; plane++) {
// turn previous plane off
if (plane==0) {
expander.digitalWrite( PlanePin[CUBESIZE-1], LOW );
} else {
expander.digitalWrite( PlanePin[plane-1], LOW );
}
// load current plane pattern data into ports
ledpin = 0;
for (ledrow=0; ledrow<CUBESIZE; ledrow++) {
for (ledcol=0; ledcol<CUBESIZE; ledcol++) {
digitalWrite( LEDPin[ledpin++], PatternBuf[patbufidx] & (1 << ledcol) );
}
patbufidx++;
}
// turn current plane on
expander.digitalWrite( PlanePin[plane], HIGH );
// delay PLANETIME us
delayMicroseconds( PLANETIME );
} // for plane
} // while <EndTime
} while (DisplayTime > 0); // read patterns until time=0 which signals end
}
I changed digitalWrite of PlanePin to LOW from HIGH and to HIGH from LOW becouse I read that expander gives more currency on LOW state. But still no luck.
I would be thankful for any advice on this issue 
Thanks in advance!
Rafał
