Implement lcdd.py (status daemon)

README.md

@@ -21,3 +21,19 @@ lcd.py
 
 Commandline interface for the LCD plate.
 
+
+lcdd.py
+-------
+
+Status display "daemon" program.
+
+1) Start a server:
+    ./lcdd.py --socket comm.sock --server --title "First line"
+
+2) Talk to it using the client:
+    ./lcdd.py --socket comm.sock --client --message "p10"
+    ./lcdd.py --socket comm.sock --client --message "quit"
+
+Available messages:
+ * `quit`: shut down server
+ * `pXXX`: display a percentage bar between 0% and 100%

lcdd.py

+#!/usr/bin/python
+
+import argparse
+import sys
+import os
+import atexit
+import socket
+
+from Adafruit_CharLCDPlate import Adafruit_CharLCDPlate
+
+# character that resembles a block on the display:
+BLOCKCHAR='\xFF'
+
+def info(msg):
+	'''Print a message string to stderr.'''
+	print >> sys.stderr, msg
+
+def opensock(sockaddress, verbose):
+	'''Open a unix domain socket and return its handle.
+
+	Also registers a cleanup callback that ensures that the socket will be removed at exit.
+	'''
+	def removesock(sockaddress, verbose):
+		'''Remove the socket file'''
+		if verbose >= 2:
+			info("Removing socket file: "+sockaddress)
+		os.unlink(sockaddress)
+
+	if verbose >= 2:
+		info("Using socket: "+sockaddress)
+	sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+	sock.bind(sockaddress)
+	# make sure we delete the socket file:
+	atexit.register(removesock,sockaddress,verbose)
+	return sock
+
+def connectsock(sockaddress, verbose):
+	'''Connect to an existing unix domain socket and return its handle.'''
+	def closesock(sock, verbose):
+		if verbose >= 2:
+			info("Closing socket...")
+		sock.close
+	if verbose >= 2:
+		info("Using socket: "+sockaddress)
+	sock = socket.socket(socket.AF_UNIX, socket.SOCK_STREAM)
+	sock.connect(sockaddress)
+	atexit.register(closesock,sock,verbose)
+	return sock
+
+def setup_display(title,verbose):
+	'''Set up the initial display parameters and text.
+
+	Also registers a cleanup callback that clears the display and turns off the backlight at exit.'''
+	def cleanup_display(verbose):
+		if verbose >= 1:
+			info("Closing display...")
+		lcd.clear()
+		lcd.backlight(lcd.OFF)
+
+	if verbose >= 1:
+		info("Setting up display...")
+	# Initialize the LCD plate.
+	lcd = Adafruit_CharLCDPlate()
+	atexit.register(cleanup_display,verbose)
+	lcd.message(title)
+	return lcd
+
+def display(title, percentage, verbose):
+	'''Set the first line to title, and print a bar graph in the second line.'''
+	if percentage < 0:
+		percentage = 0
+	elif percentage > 100:
+		percentage = 100
+	if verbose >= 2:
+		info("Display: {0}\\n{1}%".format(title, percentage))
+	nfill = percentage//10
+	# message:
+	# |title           |
+	# |XXXXXXXXXX  100%| (X's are left aligned, percentage right aligned)
+	lcd.message(title + '\n{0:<10}  {1:>3}%'.format((BLOCKCHAR*nfill), percentage)) 
+
+### assemble command line syntax:
+cmdparser = argparse.ArgumentParser(description='Commandline interface to the LCD plate.')
+cmdparser.add_argument('--verbose','-v',action='count')
+cmdparser.add_argument('--backlight','-b'
+		,help='Set backlight to color.\nPossible colors: red, yellow, green, teal, blue, violet, white, on, off'
+		,nargs='?'
+		,const='on'
+		)
+cmdparser.add_argument('--socket','-S'
+		,help='Use socket for communication. Default: %(default)s'
+		,default='/var/run/lcdd.sock'
+		,nargs='?'
+		)
+cmdparser.add_argument('--message'
+		,help='Set the message to send to the server. Default: %(default)s (ignored in server mode)'
+		,nargs='?'
+		,default='quit'
+		)
+cmdparser.add_argument('--title'
+		,help='Set the title displayed in the first line (only used in server mode).'
+		,nargs='?'
+		,default='+x+x+x+x+x+x+x+x'
+		)
+group = cmdparser.add_mutually_exclusive_group(required=True)
+group.add_argument('--server','-s'
+		,help='Start up in server mode.'
+		,action='store_true'
+		)
+group.add_argument('--client','-c'
+		,help='Connect to server as client.'
+		,action='store_true'
+		)
+
+args = cmdparser.parse_args()
+
+if args.server:
+	if args.verbose >= 1:
+		info("Server mode")
+	lcd = setup_display(args.title,verbose=args.verbose)
+	# bind to server socket:
+	sock = opensock( args.socket, verbose=args.verbose)
+	quit = False
+	sock.listen(1)
+	while not quit:
+		connection, addr = sock.accept()
+		data = connection.recv(4)
+		if args.verbose >= 2:
+			info("Message received: "+data)
+		if data == 'quit':
+			if args.verbose >= 1:
+				info("Quit requested.")
+			quit = True
+		elif data[0:1] == 'p':
+			value = int(data[1:])
+			if 0 <= value <= 100:
+				display(args.title,value,verbose=args.verbose)
+else:
+	if args.verbose >= 1:
+		info("Client mode")
+	try:
+		sock = connectsock( args.socket, verbose=args.verbose)
+	except socket.error, msg:
+		info("Could not connect to socket: " + str(msg))
+		sys.exit(1)
+	try:
+		if args.verbose >= 1:
+			info("Sending message: "+args.message)
+		sock.sendall(args.message)
+	except socket.error, msg:
+		info("Could not send message: " + str(msg))
+		sys.exit(1)