tool to verify checksum of NMEA-Data, can read from file/serial and write to file/serial

 # ./nmea_checker 
 NMEA Checker, version 0.2
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 NMEA Checker reads Input from one serial line or file and verifies
  the NMEA checksum. If ok, NMEA sentence will be transferred to
  the Output device or file.
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 usage: nmea_checker [-d] [-t] InputFile|InputDevice [OutputFile|OutputDevice]
        device can also be '/dev/ptmx' pseudoterminal
 -d      log all the data to nmea_checker_[all|ok|wrong].log
 -t      include timestamp in log-data (but not in output file)
 
 example: ./nmea_checker -d -t /dev/ttyUSB0 /dev/ttyUSB1