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:

#T0:23:respawn:/sbin/getty -L ttyAMA0 115200 vt100

#c2:2345:respawn:/sbin/agetty -8 -s 115200 ttyAMA0

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('

')[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()

The TextStar Serial LCD Display from Cat's Whisker Technologies is a nice little 16x2 display. It's quite a sophisticated screen including 4 buttons to transmit characters too. It's a perfect companion for the Raspberry Pi as you can run it straight off the 3.3v supply and TTL serial pins without the need for an RS232 converter like a MAX232. It couldn't be easier!As the video shows I have written some software to use the 4 buttons as page buttons.The ip address screen is really useful if you are set up for DHCP. Just plug in and it shows you the address needed to access your Raspberry Pi on the network.On Raspbian:On Arch:and then reboot.