Raspberry Pi GPIO LED Binary Clock driven by the MCP23017 port expander

mcp23017.py

import smbus
import time
from datetime import datetime

bus = smbus.SMBus(1)

DEVICE = 0x20 # Device address (A0-A2)
IODIRA = 0x00
OLATA  = 0x14
GPIOA  = 0x12

# Set all GPA pins as outputs
bus.write_byte_data(DEVICE, IODIRA, 0x00)

# Set output all 7 output bits to 0
bus.write_byte_data(DEVICE,OLATA,0)

try:
  while True:
    for LedOut in range(0,60):
      # Count from 1 to 255

      now = datetime.now()
      current_seconds = int(now.strftime("%S"))
      bus.write_byte_data(DEVICE, OLATA, current_seconds)
#      print(current_seconds)

#      bus.write_byte_data(DEVICE, OLATA, LedOut)
#      print(LedOut)

      time.sleep(0.1)
except KeyboardInterrupt:
  # Set all bits to zero
  bus.write_byte_data(DEVICE, OLATA, 0)

sudo apt-get install -y i2c-tools

pip3 install smbus

Also requires the i2c interface to be enabled on the Raspberry Pi. Enable that using sudo raspi-config, and then reboot.

Open a terminal and check the I2C address by typing in sudo i2cdetect -y 1

Helpful resource: https://learn.adafruit.com/adafruits-raspberry-pi-lesson-4-gpio-setup/configuring-i2c