chirp.py

#!/usr/bin/env python
from __future__ import print_function

import smbus, time, sys, argparse

class Chirp:
  def __init__(self, bus=1, address=0x20):
    self.bus_num = bus
    self.bus = smbus.SMBus(bus)
    self.address = address
    self.reset()
    self.version()

  def reset(self):
    self.write(0x06)
    time.sleep(1)

  def version(self):
    self.write(0x07)
    ver = self.read()
    print("version", hex(ver))

  def read(self):
    ok = False
    val = None
    count = 0
    while not ok:
      try:
        # sometime reading raises an IOError, i don't know why.
        val = self.bus.read_byte(self.address)
        ok = True
      except IOError:
        time.sleep(0.1)
        count = count + 1
        if count > 5:
          raise
        pass
    return val

  def write(self, reg):
    count = 0
    ok = False
    while not ok:
      try:
        # sometime writing raises an IOError, i don't know why.
        self.bus.write_byte(self.address, reg)
        ok = True
      except IOError, e:
        time.sleep(0.1)
        count = count + 1
        if count > 5:
          print(e)
          # will this just break everything?
          time.sleep(10)

  def get_reg(self, reg):
    self.write(reg)
    time.sleep(0.1)

    b1 = self.read()
    b2 = self.read()

    # if the chrip has no data it sends
    # 0xff, use this to re-sync in case we loose values.
    t = self.read()
    while t != 0xff:
      t = self.read()
    return (b1 << 8) + b2

  def cap_sense(self):
    return self.get_reg(0)

  def temp(self):
    return self.get_reg(5)

  def light(self):
    self.write(3)
    time.sleep(1.5)
    return self.get_reg(4)

  def set_address(self, sa):
    self.write(0x1)
    self.write(sa)
    self.reset()

  def __repr__(self):
    return "<Chirp sensor on bus %d, addr 0x%02x>" % (self.bus_num, self.address)

if __name__ == "__main__":
  addr = 0x50
  bus = 0

  parser = argparse.ArgumentParser(description='Work with Chirp\'s')

  parser.add_argument('--set-address', type=str,
      help='set the chirps i2c address to this address')

  parser.add_argument('address',
      type=str,default="0x20",
      help='the chirp\'s i2c address')

  parser.add_argument('bus',
      type=int, default=1, nargs='?',
      help='the i2c bus to look at')

  args = parser.parse_args()

  bus = args.bus
  addr = args.address
  try:
    if addr.startswith("0x"):
      addr = int(addr, 16)
    else:
      addr = int(addr)
  except ValueError:
    parser.error("can't parse %s as an i2c address" % (args.address))
    raise SystemExit

  chirp = Chirp(bus, addr)

  if args.set_address:
    sa = args.set_address
    try:
      if sa.startswith("0x"):
        sa = int(sa, 16)
      else:
        sa = int(sa)
    except ValueError:
      parser.error("can't parse %s as an i2c address" % (args.set_address))
      raise SystemExit

    print("Setting the chirp's i2c address to 0x%x" % (sa))
    chirp.set_address(sa)
    print("done")
    raise SystemExit

  while True:
    chirp.reset()
    print("cap", chirp.cap_sense())
    chirp.reset()
    print("temp", chirp.temp() / 10.0)
    chirp.reset()
    print("light", chirp.light())
    time.sleep(1)
    print()