text: # Software License Agreement (BSD License)
  #
  # Copyright (c) 2013, Eric Perko
  # All rights reserved.
  #
  # Redistribution and use in source and binary forms, with or without
  # modification, are permitted provided that the following conditions
  # are met:
  #
  #  * Redistributions of source code must retain the above copyright
  #    notice, this list of conditions and the following disclaimer.
  #  * Redistributions in binary form must reproduce the above
  #    copyright notice, this list of conditions and the following
  #    disclaimer in the documentation and/or other materials provided
  #    with the distribution.
  #  * Neither the names of the authors nor the names of their
  #    affiliated organizations may be used to endorse or promote products derived
  #    from this software without specific prior written permission.
  #
  # THIS SOFTWARE IS PROVIDED BY THE COPYRIGHT HOLDERS AND CONTRIBUTORS
  # "AS IS" AND ANY EXPRESS OR IMPLIED WARRANTIES, INCLUDING, BUT NOT
  # LIMITED TO, THE IMPLIED WARRANTIES OF MERCHANTABILITY AND FITNESS
  # FOR A PARTICULAR PURPOSE ARE DISCLAIMED. IN NO EVENT SHALL THE
  # COPYRIGHT OWNER OR CONTRIBUTORS BE LIABLE FOR ANY DIRECT, INDIRECT,
  # INCIDENTAL, SPECIAL, EXEMPLARY, OR CONSEQUENTIAL DAMAGES (INCLUDING,
  # BUT NOT LIMITED TO, PROCUREMENT OF SUBSTITUTE GOODS OR SERVICES;
  # LOSS OF USE, DATA, OR PROFITS; OR BUSINESS INTERRUPTION) HOWEVER
  # CAUSED AND ON ANY THEORY OF LIABILITY, WHETHER IN CONTRACT, STRICT
  # LIABILITY, OR TORT (INCLUDING NEGLIGENCE OR OTHERWISE) ARISING IN
  # ANY WAY OUT OF THE USE OF THIS SOFTWARE, EVEN IF ADVISED OF THE
  # POSSIBILITY OF SUCH DAMAGE.
  
  
  # Check the NMEA sentence checksum. Return True if passes and False if failed
  def check_nmea_checksum(nmea_sentence):
      split_sentence = nmea_sentence.split(b'*')
      if len(split_sentence) != 2:
          #No checksum bytes were found... improperly formatted/incomplete NMEA data?
          return False
      transmitted_checksum = split_sentence[1].strip()
  
      #Remove the $ at the front
      data_to_checksum = split_sentence[0][1:]
      checksum = 0
      for c in data_to_checksum:
          if type(c) is int:
              checksum ^= c
          else:
              checksum ^= ord(c)
      
      return (b"%02X" % checksum) == transmitted_checksum.upper()
  