#!/usr/bin/env python
#
# dmx512.py - DMX512 class
#             Works with the following adapters:
#               - DMXKing ultraDMX Micro
#
# Copyright 2017 Todd Shadburn <tshadburn@opencomputingsolutions.com>
#
# This program is free software; you can redistribute it and/or
# modify it under the terms of the GNU General Public License
# as published by the Free Software Foundation; either version 2
# of the License, or (at your option) any later version.
#
# This program is distributed in the hope that it will be useful,
# but WITHOUT ANY WARRANTY; without even the implied warranty of
# MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
# GNU General Public License for more details.
#
# You should have received a copy of the GNU General Public License
# along with this program; if not, write to the Free Software Foundation, Inc.,
# 51 Franklin Street, Fifth Floor, Boston, MA  02110-1301, USA.



import serial


#char 126 is 7E in hex. It's used to start all DMX512 commands
DMXOPEN=chr(126)

#char 231 is E7 in hex. It's used to close all DMX512 commands
DMXCLOSE=chr(231)

# Adapter initialization string #1
DMXINIT1= chr(03)+chr(02)+chr(0)+chr(0)+chr(0)

# Adapter initialization string #2
DMXINIT2= chr(10)+chr(02)+chr(0)+chr(0)+chr(0)

class DMX512(object):
	def __init__(self, device=None, maxchannels=512):
		self.device = device
		if maxchannels > 512:
			maxchannels = 512
		self.maxchannels = maxchannels+1 # One extra byte needed
		self.dmxdata = [chr(0)] * (self.maxchannels)
		chh = int(self.maxchannels / 256)
		chl = int(self.maxchannels - (chh * 256))
		print 'DEBUG maxchannels=%d chh=%d chl=%d' % (self.maxchannels, chh, chl)
		self.dmx_length = chr(6) + chr(chl) + chr(chh)
		self.sfd = serial.Serial(self.device)
		# Init DMX adapter
		self.sfd.write( DMXOPEN+DMXINIT1+DMXCLOSE)
		self.sfd.write( DMXOPEN+DMXINIT2+DMXCLOSE)
		return

	def close(self):
		self.sfd.close()
		return

	def set(self, channel, value):
		"""
		Change the value for a single channel
		(Does not push the change to the adapter)
		"""
		if channel < 1 or channel > 512:
			raise ValueError('DMX channel must be between 1 and 512')
		self.dmxdata[channel] = chr(value)
		return

	def update(self):
		"""
		Push the current channel settings to the adapater
		"""
		sdata = ''.join(self.dmxdata)
		self.sfd.write(DMXOPEN+self.dmx_length+sdata+DMXCLOSE)
		return