My 7-Segment Display

I ordered the device from Adafruit. The main reason was to check out getting a second I2C device to work. Here's how I wired it from the Pi:

To get that far I followed the directions at--

http://learn.adafruit.com/adafruit-led-backpack/0-dot-56-seven-segment-backpack

I found soldering the 24 tiny pins to connect the display to the "backpack" a trial, but surprise, surprise -- it worked with their example 24-hour clock program first try. I had previously downloaded --

Adafruit-Raspberry-Pi-Python-Code-master/Adafruit_LEDBackpack

(Do you think they could make the directory names any longer?)

I wanted my clock to display 12-hour/AM/PM time. Here's my rework of the software:

#!/usr/bin/python

import time

import datetime

import signal

import sys

from Adafruit_7Segment import SevenSegment

def signal_handler(signal, frame): # to stop the clock

    print 'You pressed Ctrl+C!'

    SevenSegment(address=0x70) #clear display

    sys.exit(0)

signal.signal(signal.SIGINT, signal_handler)

segment = SevenSegment(address=0x70)

lastHour = -1

print "Press CTRL+C to exit"

# Continually update the time on a 4 char, 7-segment display

while(True):

  now = datetime.datetime.now() # get 24-hour time values

  hour = now.hour

  pm = False

  # Set hours

  if hour != lastHour:   # don't change display

    lastHour = hour

    if hour > 11: # change to 12 hour clock

      hour -= 12

      pm = True

      if hour == 0: # just after midnight

        hour = 12

      if int(hour / 10) == 0:  # turn off leading zero

        segment = SevenSegment(address=0x70)  # turns all digits off

    if int(hour / 10) != 0:    

      segment.writeDigit(0, int(hour / 10))     # Tens

    segment.writeDigit(1, hour % 10)          # Ones

  # Set minutes

  minute = now.minute

  segment.writeDigit(3, int(minute / 10))   # Tens

  segment.writeDigit(4, minute % 10, pm)        # Ones + PM dot

  # turn on colon

  segment.setColon(1)

  time.sleep(60)    # update in 1 minute -- may be 1 minute slow 

One of the irritations of Python is that a program like this can only be executed from the directory its local "import" file is in. There are ways around this but it's enough to make C language attractive. 

Most importantly, both of my I2C-connected devices still work. And I can add more. From two GPIO pins (3=SLA, 5=SCL), many devices!