Test plugin for I2C SIP interfase to relay boards

i2c_plugin.py

#!/usr/bin/env python

# Python 2/3 compatibility imports
from __future__ import print_function

# standard library imports
import json
import smbus
import subprocess
import time

# local module imports
from blinker import signal
import gv  # Get access to SIP's settings, gv = global variables
from sip import template_render
from urls import urls  # Get access to SIP's URLs
import web
from webpages import ProtectedPage

# Add a new url to open the data entry page.
# fmt: off
urls.extend(
    [
        u"/i2c", u"plugins.i2c_plugin.docs", #### Need to create this ####
    ]
)
# fmt: on

# Add this plugin to the plugins menu
gv.plugin_menu.append([u"I2C_plugin", u"/i2c"])


bus = smbus.SMBus(1)
addr = 0x20 # starting I2C chip address


#### Not sure if this is needed ####
# if commands["gpio"]:
#     gv.use_gpio_pins = False
# else:
#     gv.use_gpio_pins = True


#### Control relay when signal received ####
def on_zone_change(name, **kw):
    """ Switch relays when core program signals a change in station state."""
    global addr
    for b in range(gv.sd[u"nbrd"]): # for each group of 8 stations (boards/I2C chips)
        addr += b # b is 0 based, so first iteration b = 0, next iteration b = 1 etc
        byte = 0xFF # start with full byte (all 1's).
        for s in range(8): # for each station per board/I2C chip
            sid = b * 8 + s  # station index in gv.srvals           
            if gv.srvals[sid]:  # station is on
                byte = byte ^ (1 << s) # use exclusive or to set station bit to 0
        print("writing byte: ", byte)
        bus.write_byte(addr, byte)                     
    return


zones = signal(u"zone_change")
zones.connect(on_zone_change)

################################################################################
# Web pages:                                                                   #
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#### Need to create documentation page ####