import machine
import mcp
import time
from machine import I2C

i2c=I2C(sda=machine.Pin(23), scl=machine.Pin(22))

reg=bytearray(1)

a = 0x20

reg[0]=0xff
i2c.writeto_mem(a, 0x01, reg)  # All Input Register B
i2c.writeto_mem(a, 0x0d, reg)  # All Pullups Register B

# Note: Man könnte die Polarität ändern, und so die GPIO-Bits invertieren
# i2c.writeto_mem(a, 0x03, reg)

reg[0]=0x00
i2c.writeto_mem(a, 0x00, reg)  # All Output Register A

# GPIO 0x12 (A), 0x13 (B)

rega=bytearray(1)
regb=bytearray(1)
old = 0
while True:
    rega[0]=(rega[0]+1)%256
    i2c.writeto_mem(a, 0x12, rega)  # Write to GPIOA
    i2c.readfrom_mem_into(a, 0x13,regb) # Read from GPIOB
    if (regb[0]!=old):
        print(bin(regb[0]))
        old=regb[0]
#    time.sleep_ms(100)