import utime
import ustruct

At reset, the device's ports are inputs with a high value resistor pull-ups to VDD

If relays turning on during power up are a problem. Add a pull down resistor to each

relay transistor base.

CmdBys={
'IN_P0':0x00, #Read Input port0
'IN_P1':0x01, #Read Input port1
'OUT_P0':0x02, #Write Output port0
'OUT_P1':0x03, #Write Output port1
'INV_P0':0x04, #Input Port Polarity Inversion port0/1 if B11111111 is
'INV_P1':0x05, #written input polarity is inverted
'CONFIG_P0':0x06,#Configuration port0/1 configures the direction of the
'CONFIG_P1':0x07 #I/O pins, 0 is output 1 is input
}
class PCA9555:
#with no jumpers the full address is 1 0 0 1 1 1
#1 0 0 A2 A1 A0 0x27 is the default address for the DFR0013 board with no jumpers.
#0x20 is address for the DFR0013 board with all jumpers.
def init(self, i2c, address=0x20):
self.i2c = i2c
self.address = address

self.reset()

def _write(self, address, value):    #这里的address为器件内部地址
    self.i2c.writeto_mem(self.address, address, bytearray([value]))

def _read(self, address):
    return self.i2c.readfrom_mem(self.address, address, 1)[0]

def reset(self):

self._write(0x00, 0x00) # Mode1

def Output(self, Outvalue=None):    #高八位给端口1，低八位给端口0
    self._write(CmdBys['CONFIG_P0'], 0x00)
    self._write(CmdBys['CONFIG_P1'], 0x00)
    if Outvalue is None:
        self._write(CmdBys['OUT_P0'], 0x00)
        self._write(CmdBys['OUT_P1'], 0x00)
    else:
        value0=Outvalue&0xff
        value1=(Outvalue>>8)&0xff
        self._write(CmdBys['OUT_P0'], value0)
        self._write(CmdBys['OUT_P1'], value1)


def Input(self):
    self._write(CmdBys['CONFIG_P0'], 0xff)
    value0=self._read(CmdBys['IN_P0'])
    self._write(CmdBys['CONFIG_P0'], 0xff)
    value1=self._read(CmdBys['IN_P1'])
    Invalue=(value1<<8)|value0
    return Invalue