Arduino library for PCA9536 4-Bit I2C and SMBus I/O Expander With Configuration Registers
#include "PCA9536.h"
PCA9536 ioex;
uint32_t port = 0;
void setup()
{
    ioex.setup();
}
void loop()
{
    ioex.output(port % 16);
    ++port;
    delay(1000);
}MIT