Export FreeStyle Lite data from serial USB cable to CSV

glucometer_export.py

""" Extract FreeStyle Lite data from serial USB cable to CSV.
Defaults for Linux or MacOS systems """

import argparse
import glob
import os
import re
import serial
from csv import writer

from datetime import datetime, date


def export_csv(tty_path, out):
    csv = writer(out)
    csv.writerow(('datetime', 'bg'))

    def read_tty():
        # readlines() can take a while. debug partial reads
        # with tty.readlines(100).
        tty = serial.Serial(tty_path, baudrate=19200, timeout=5)
        tty.write(b"mem")  # ask device to recite memory
        for line in tty.readlines():
            yield line.decode('ascii')

    def parse_datetime(line):
        # two expressions since June isn't %b but %B
        # 099  Nov  04 2015 01:09 00 0x00
        # 180  June 01 2016 00:43 00 0x00
        date_str = re.sub(' +', ' ', line[5:23])
        try:
            return datetime.strptime(date_str, "%b %d %Y %H:%M")
        except ValueError:
            return datetime.strptime(date_str, "%B %d %Y %H:%M")

    line = None
    for line in read_tty():
        # lines look like
        # 099  Nov  04 2015 01:09 00 0x00
        # 180  June 01 2016 00:43 00 0x00
        try:
            dt = parse_datetime(line)
        except ValueError:
            # beginning and ending lines aren't relevant
            print("skipping", repr(line))
        else:
            bg = int(line[0:3], 10)
            csv.writerow((dt, bg))

    if line is None:
        raise IOError("Nothing read from glucometer. "
                      "Ensure that device is connected properly")


def guess_tty(arg):
    """ Guess active ttyUSB """
    if os.name == 'posix':
        path = '/dev/ttyUSB*'

        usb_serial = glob.glob(path)
        if not usb_serial:
            raise argparse.ArgumentError(arg,
                    "No {} matches found. Ensure your device is connected "
                    "or look for other places that your ttyUSB device may be."
                    .format(path))
        if len(usb_serial) > 1:
            raise argparse.ArgumentError(arg,
                "Multiple paths matching {} were found. "
                "Specify --tty from {}".format(path, '\n'.join(usb_serial)))
        else:
            return usb_serial[0]
    else:
        raise argparse.ArgumentError(arg,
            "Could not guess where tty device would be")


if __name__ == '__main__':
    a = argparse.ArgumentParser(description=__doc__)
    tty_arg = a.add_argument("--tty",
        help="Full path to cable. Defaults to guessing /dev/ttyUSB*")

    default_csv = "bgs-{}.csv".format(date.today().isoformat())
    a.add_argument("-o", "--out",
        default=default_csv,
        metavar="CSV",
        help="Csv out path. Defaults to {}".format(default_csv),
        type=argparse.FileType('w'))

    args = a.parse_args()
    # using `or` instead of default to allow it to raise errors
    # when not specified but be overwriteable
    export_csv(args.tty or guess_tty(tty_arg), args.out)

requirements.txt

pyserial