From f7fde8b5a659b5b7de7d00cddb28c20d3c691d37 Mon Sep 17 00:00:00 2001 From: =?UTF-8?q?Diego=20Elio=20Petten=C3=B2?= Date: Sat, 3 Aug 2013 21:28:43 +0100 Subject: Add support for checksum verification for the otultra2 driver. This introduced some changes in the Exception class to simplify the code, and at the same time it adds a module for multiple lifescan drivers to share code (multiple OneTouch protocols share the same checksum for instance). --- glucometerutils/drivers/lifescan_common.py | 70 ++++++++++++++++++++++++++++++ glucometerutils/drivers/otultra2.py | 33 +++++++------- glucometerutils/exceptions.py | 13 +++--- test/test_lifescan.py | 29 +++++++++++++ test/test_otultra2.py | 23 ++++++++-- 5 files changed, 139 insertions(+), 29 deletions(-) create mode 100644 glucometerutils/drivers/lifescan_common.py create mode 100644 test/test_lifescan.py diff --git a/glucometerutils/drivers/lifescan_common.py b/glucometerutils/drivers/lifescan_common.py new file mode 100644 index 0000000..ac25d22 --- /dev/null +++ b/glucometerutils/drivers/lifescan_common.py @@ -0,0 +1,70 @@ +# -*- coding: utf-8 -*- +"""Common utility functions for LifeScan meters.""" + +__author__ = 'Diego Elio Pettenò' +__email__ = 'flameeyes@flameeyes.eu' +__copyright__ = 'Copyright © 2013, Diego Elio Pettenò' +__license__ = 'GPL v3 or later' + +import ctypes + +from glucometerutils import exceptions + + +class MissingChecksum(exceptions.InvalidResponse): + """The response misses the expected 4-digits checksum.""" + def __init__(self, response): + self.message = 'Response is missing checksum: %s' % response + + +class InvalidChecksum(exceptions.InvalidResponse): + def __init__(self, expected, gotten): + self.message = ( + 'Response checksum not matching: %04x expected, %04x gotten' % + (expected, gotten)) + + +class InvalidSerialNumber(exceptions.Error): + """The serial number is not as expected.""" + def __init__(self, serial_number): + self.message = 'Serial number %s is invalid.' % serial_number + + +def calculate_checksum(bytestring): + """Calculate the "CRC16 Sick" style checksum for LifeScan protocols. + + Args: + bytestring: the string of which the checksum has to be calculated. + + Returns: + A 16-bit integer that is the checksum for the input. + + Credits for this code go to Christian Navalici, who implemented it in his + library at https://github.com/cristianav/PyCRC/ . + """ + crcValue = 0x0000 + prev_c = 0x0000 + + for idx, c in enumerate(bytestring): + short_c = 0x00ff & c + + idx_previous = idx - 1 + short_p = ( 0x00ff & prev_c) << 8; + + if ( crcValue & 0x8000 ): + crcValue = ctypes.c_ushort(crcValue << 1).value ^ 0x8005 + else: + crcValue = ctypes.c_ushort(crcValue << 1).value + + crcValue &= 0xffff + crcValue ^= ( short_c | short_p ) + + prev_c = short_c + + # After processing, the one's complement of the CRC is calcluated and the + # two bytes of the CRC are swapped. + low_byte = (crcValue & 0xff00) >> 8 + high_byte = (crcValue & 0x00ff) << 8 + crcValue = low_byte | high_byte; + + return crcValue diff --git a/glucometerutils/drivers/otultra2.py b/glucometerutils/drivers/otultra2.py index f453dc9..ebfda8f 100644 --- a/glucometerutils/drivers/otultra2.py +++ b/glucometerutils/drivers/otultra2.py @@ -13,19 +13,7 @@ import serial from glucometerutils import common from glucometerutils import exceptions - - -class MissingChecksum(exceptions.InvalidResponse): - """The response misses the expected 4-digits checksum.""" - def __init__(self, response): - self.response = response - - def __str__(self): - return 'Response is missing the OT2 checksum: %s' % self.response - - -class InvalidSerialNumber(exceptions.Error): - """The serial number is not ending with Y as expected.""" +from glucometerutils.drivers import lifescan_common class Device(object): @@ -62,11 +50,22 @@ class Device(object): match = self._RESPONSE_MATCH.match(line) if not match: - raise MissingChecksum(line) + raise lifescan_common.MissingChecksum(line) + + response, checksum_string = match.groups() + + try: + checksum_given = int(checksum_string, 16) + checksum_calculated = lifescan_common.calculate_checksum( + bytes(response, 'ascii')) - response, checksum = match.groups() + if checksum_given != checksum_calculated: + raise lifescan_common.InvalidChecksum(checksum_given, + checksum_calculated) + except ValueError: + raise lifescan_common.InvalidChecksum(checksum_given, + None) - # TODO(flameeyes) check that the checksum is actually valid return response def _send_oneliner_command(self, cmd): @@ -122,7 +121,7 @@ class Device(object): # 'Y' at the far right of the serial number is the indication of a OneTouch # Ultra2 device, as per specs. if serial_number[-1] != 'Y': - raise InvalidSerialNumber('Serial number %s is invalid.' % serial_number) + raise lifescan_common.InvalidSerialNumber(serial_number) return serial_number diff --git a/glucometerutils/exceptions.py b/glucometerutils/exceptions.py index 00c9e91..1acf9a4 100644 --- a/glucometerutils/exceptions.py +++ b/glucometerutils/exceptions.py @@ -9,22 +9,19 @@ __license__ = 'GPL v3 or later' class Error(Exception): """Base class for the errors.""" + def __str__(self): + return self.message + class InvalidResponse(Error): """The response received from the meter was not understood""" def __init__(self, response): - self.response = response - - def __str__(self): - return 'Invalid response received:\n%s' % self.response + self.message = 'Invalid response received:\n%s' % response class InvalidGlucoseUnit(Error): """Unable to parse the given glucose unit""" def __init__(self, unit): - self.unit = unit - - def __str__(self): - return 'Invalid glucose unit received:\n%s' % self.unit + self.message = 'Invalid glucose unit received:\n%s' % unit diff --git a/test/test_lifescan.py b/test/test_lifescan.py new file mode 100644 index 0000000..774567d --- /dev/null +++ b/test/test_lifescan.py @@ -0,0 +1,29 @@ +# -*- coding: utf-8 -*- +"""Tests for the LifeScan Common functions.""" + +__author__ = 'Diego Elio Pettenò' +__email__ = 'flameeyes@flameeyes.eu' +__copyright__ = 'Copyright © 2013, Diego Elio Pettenò' +__license__ = 'GPL v3 or later' + +import os +import sys +import unittest + +sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))) + +from glucometerutils import common +from glucometerutils.drivers import lifescan_common +from glucometerutils import exceptions + + +class TestOTUltra2(unittest.TestCase): + def testChecksum(self): + checksum = lifescan_common.calculate_checksum(bytes('T', 'ascii')) + self.assertEqual(0x5400, checksum) + + checksum = lifescan_common.calculate_checksum(bytes('TestString', 'ascii')) + self.assertEqual(0x0643, checksum) + +if __name__ == '__main__': + unittest.main() diff --git a/test/test_otultra2.py b/test/test_otultra2.py index ba577c3..6ffea83 100644 --- a/test/test_otultra2.py +++ b/test/test_otultra2.py @@ -15,6 +15,7 @@ import mock sys.path.append(os.path.dirname(os.path.dirname(os.path.abspath(__file__)))) from glucometerutils import common +from glucometerutils.drivers import lifescan_common from glucometerutils.drivers import otultra2 from glucometerutils import exceptions @@ -30,7 +31,7 @@ class TestOTUltra2(unittest.TestCase): def testMissingChecksum(self): self.mock_readline.return_value = bytes('INVALID', 'ascii') - self.assertRaises(otultra2.MissingChecksum, + self.assertRaises(lifescan_common.MissingChecksum, self.device.get_serial_number) def testShortResponse(self): @@ -40,16 +41,30 @@ class TestOTUltra2(unittest.TestCase): self.device.get_serial_number) def testInvalidResponse(self): - self.mock_readline.return_value = bytes('% 1337\r', 'ascii') + self.mock_readline.return_value = bytes('% 2500\r', 'ascii') self.assertRaises(exceptions.InvalidResponse, self.device.get_serial_number) def testInvalidSerialNumber(self): self.mock_readline.return_value = bytes( - '@ "12345678O" 1337\r', 'ascii') + '@ "12345678O" E105\r', 'ascii') - self.assertRaises(otultra2.InvalidSerialNumber, + self.assertRaises(lifescan_common.InvalidSerialNumber, + self.device.get_serial_number) + + def testInvalidChecksum(self): + self.mock_readline.return_value = bytes( + '% 1337\r', 'ascii') + + self.assertRaises(lifescan_common.InvalidChecksum, + self.device.get_serial_number) + + def testBrokenChecksum(self): + self.mock_readline.return_value = bytes( + '% 13AZ\r', 'ascii') + + self.assertRaises(lifescan_common.MissingChecksum, self.device.get_serial_number) if __name__ == '__main__': -- cgit v1.2.3