redbutton.py

#!/usr/bin/python

import time
import usb
import syslog
import os
import sys

def onButtonDown():
  syslog.syslog('BIG RED BUTTON PRESSED!!')
  os.system('sudo -u james -n DISPLAY=:0.0 /home/james/scripts/brb-py/onbuttonpress.sh')
  
def onButtonUp():
  syslog.syslog('BIG RED BUTTON RELEASED!!')

def findButton():
  for bus in usb.busses():
    for dev in bus.devices:
      if dev.idVendor == 0x1d34 and dev.idProduct == 0x000d:
        return dev

dev = findButton()
if dev is None:
  syslog.syslog('redbutton.py executed but no Big Red Button could be found')
  print '>>> The Big Red Button could not be found. Please plug it into a USB port.'
  sys.exit()

handle = dev.open()
interface = dev.configurations[0].interfaces[0][0]
endpoint = interface.endpoints[0]

try:
  handle.detachKernelDriver(interface)
except Exception, e:
  # It may already be unloaded.
  pass

handle.claimInterface(interface)

syslog.syslog('Started Big Red Button listener')

button_depressed = 0
button_depressed_last = 0
while 1:
  # USB setup packet. I think it's a USB HID SET_REPORT.
  result = handle.controlMsg(requestType=0x21, # OUT | CLASS | INTERFACE
                            request= 0x09, # SET_REPORT
                            value= 0x0200, # report type: OUTPUT
                            buffer="\x00\x00\x00\x00\x00\x00\x00\x02")
  
  try:
    result = handle.interruptRead(endpoint.address, endpoint.maxPacketSize)
    if result[0] == 22:
      button_depressed = 1
    else:
      button_depressed = 0
    
    if (button_depressed_last != button_depressed):
      if (button_depressed):
        onButtonDown()
      else:
        onButtonUp()
    
    button_depressed_last = button_depressed
    
    #print [hex(x) for x in result]
  except Exception, e:
    # Sometimes this fails. Unsure why.
    pass
  
  time.sleep(endpoint.interval * 0.001) # 10ms

handle.releaseInterface(interface)