Simple test connection controller matrix keyboard PCF8574

PCF8574_test.py

#!/usr/bin/env python3
"""
1. Enable I2C

sudo raspi-config

Interface Options → I2C → Enable

sudo reboot

2.  Install libraries

sudo apt update
sudo apt install -y i2c-tools python3-smbus

3. Find address i2c

i2cdetect -y -1
"""


import time
import smbus

I2C_ADDR = 0x20
bus = smbus.SMBus(1)

# P0..P2 - columns, P4..P7 - rows
COLS = [2, 1, 0]
ROWS = [6, 5, 4, 3]

KEYS = [
    ["1", "2", "3"],
    ["4", "5", "6"],
    ["7", "8", "9"],
    ["*", "0", "#"],
]



def write_pcf(value):
    bus.write_byte(I2C_ADDR, value & 0xFF)

def read_pcf():
    return bus.read_byte(I2C_ADDR)

def scan_keypad():
    for col_index, col_pin in enumerate(COLS):
    # All lines HIGH, except for current columns LOW
        value = 0xFF & ~(1 << col_pin)
        write_pcf(value)
        time.sleep(0.002)

        data = read_pcf()

        for row_index, row_pin in enumerate(ROWS):
            if not (data & (1 << row_pin)):
                return KEYS[row_index][col_index]

    return None

print("Check keypad. Press buttons. Ctrl+C - exit")

last_key = None

try:
    while True:
        key = scan_keypad()

        if key and key != last_key:
            print("Pressed", key)
            last_key = key

        if not key:
            last_key = None

        time.sleep(0.1)

except KeyboardInterrupt:
    write_pcf(0xFF)
    print("Exit")