- A: Date and time
- B: Shows the latest number entry on jerbly.uk.to - my other Raspberry Pi
- C: Twitter feed from @Raspberry_Pi
- D: eth0 and wlan0 ip addresses
Connecting it up
Simply connect the 3.3v, ground, UART TX and RX pins from the Raspberry Pi to the pins on the TextStar as show in these photos:
Setup the OS
By default there is a VT100 terminal running on /dev/AMA0 which will interfere with the software. Simply edit /etc/inittab and comment out the line like so:
On Raspbian:
#T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100On Arch:
#c2:2345:respawn:/sbin/agetty -8 -s 115200 ttyAMA0and then reboot.
Code
Cat's Whisker Technologies have good documentation for the display on their web site. Follow their instructions to configure your display for TTL and set the Baud rate so it matches your python code. I've used 9600 as this is way fast enough. I have implemented some of the special commands to control scrolling and so on as you can see in the code below. The code is also available on GitHub: screen.py
'''
Created on 21 Jul 2012
@author: Jeremy Blythe
screen - Manages the Textstar 16x2 4 button display
Read the blog entry at http://jeremyblythe.blogspot.com for more information
'''
import serial
import datetime
import time
import subprocess
import twitter
import urllib2
import json
CLEAR = chr(12)
ESC = chr(254)
BLOCK = chr(154)
POLL_TICKS = 15
REFRESH_TICKS = 300
class Display():
""" Manages the 16x2 4 button display:
on_tick called every 0.1 seconds as part of the main loop after the button read
on_poll called every 1.5 seconds
on_page called when a new page has been selected
on_refresh called every 30 seconds"""
def __init__(self,on_page=None,on_poll=None,on_tick=None,on_refresh=None):
# Start the serial port
self.ser = serial.Serial('/dev/ttyAMA0',9600,timeout=0.1)
# Callbacks
self.on_page = on_page
self.on_poll = on_poll
self.on_tick = on_tick
self.on_refresh = on_refresh
self.page = 'a'
self.poll = POLL_TICKS
self.refresh = REFRESH_TICKS
def position_cursor(self,line,column):
self.ser.write(ESC+'P'+chr(line)+chr(column))
def scroll_down(self):
self.ser.write(ESC+'O'+chr(0))
def window_home(self):
self.ser.write(ESC+'G'+chr(1))
def clear(self):
self.ser.write(CLEAR)
def run(self):
#show initial page
display.ser.write(' Starting.... ')
if self.on_page != None:
self.on_page()
#main loop
while True:
key = str(self.ser.read(1))
if key != '' and key in 'abcd':
self.page = key
self.refresh = REFRESH_TICKS
self.poll = POLL_TICKS
if self.on_page != None:
self.on_page()
else:
self.refresh-=1
if self.refresh == 0:
self.refresh = REFRESH_TICKS
if self.on_refresh != None:
self.on_refresh()
self.poll-=1
if self.poll == 0:
self.poll = POLL_TICKS
if self.on_poll != None:
self.on_poll()
if self.on_tick != None:
self.on_tick()
display = None
# Start twitter
twitter_api = twitter.Api()
def write_datetime():
display.position_cursor(1, 1)
dt=str(datetime.datetime.now())
display.ser.write(' '+dt[:10]+' '+' '+dt[11:19]+' ')
def get_addr(interface):
try:
s = subprocess.check_output(["ip","addr","show",interface])
return s.split('\n')[2].strip().split(' ')[1].split('/')[0]
except:
return '?.?.?.?'
def write_ip_addresses():
display.position_cursor(1, 1)
display.ser.write('e'+get_addr('eth0').rjust(15)+'w'+get_addr('wlan0').rjust(15))
def write_twitter():
display.position_cursor(1, 1)
try:
statuses = twitter_api.GetUserTimeline('Raspberry_Pi')
twitter_out = BLOCK
for s in statuses:
twitter_out+=s.text.encode('ascii','ignore')+BLOCK
display.ser.write(twitter_out[:256])
except:
display.ser.write('twitter failed'.ljust(256))
def write_recent_numbers():
display.position_cursor(1, 1)
try:
result = urllib2.urlopen("http://jerbly.uk.to/get_recent_visitors").read()
j = json.loads(result)
if len(j) > 0:
entry = str(j[0]['numbers'][-1:])+' '+j[0]['countryName']
display.ser.write(entry.ljust(32))
else:
display.ser.write('No entries found'.ljust(32))
except:
display.ser.write('jerbly.uk.to failed'.ljust(32))
# Callbacks
def on_page():
display.clear()
display.window_home()
if display.page == 'a':
write_datetime()
elif display.page == 'b':
write_recent_numbers()
elif display.page == 'c':
write_twitter()
elif display.page == 'd':
write_ip_addresses()
def on_poll():
if display.page == 'c':
display.scroll_down()
def on_tick():
if display.page == 'a':
write_datetime()
def on_refresh():
if display.page == 'b':
write_recent_numbers()
elif display.page == 'c':
write_twitter()
elif display.page == 'd':
write_ip_addresses()
display = Display(on_page, on_poll, on_tick, on_refresh)
display.run()
plus a few extra jumper wires to give me 3 LEDs to control and two push button inputs:
