Initial commit.

Adafruit_PureIO/smbus.py

@@ -0,0 +1,295 @@
+# Copyright (c) 2016 Adafruit Industries
+# Author: Tony DiCola
+#
+# Permission is hereby granted, free of charge, to any person obtaining a copy
+# of this software and associated documentation files (the "Software"), to deal
+# in the Software without restriction, including without limitation the rights
+# to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+# copies of the Software, and to permit persons to whom the Software is
+# furnished to do so, subject to the following conditions:
+#
+# The above copyright notice and this permission notice shall be included in
+# all copies or substantial portions of the Software.
+#
+# THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+# IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+# FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+# AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+# LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+# OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN
+# THE SOFTWARE.
+from ctypes import *
+from fcntl import ioctl
+import struct
+
+# I2C C API constants (from linux kernel headers)
+I2C_M_TEN             = 0x0010  # this is a ten bit chip address
+I2C_M_RD              = 0x0001  # read data, from slave to master
+I2C_M_STOP            = 0x8000  # if I2C_FUNC_PROTOCOL_MANGLING
+I2C_M_NOSTART         = 0x4000  # if I2C_FUNC_NOSTART
+I2C_M_REV_DIR_ADDR    = 0x2000  # if I2C_FUNC_PROTOCOL_MANGLING
+I2C_M_IGNORE_NAK      = 0x1000  # if I2C_FUNC_PROTOCOL_MANGLING
+I2C_M_NO_RD_ACK       = 0x0800  # if I2C_FUNC_PROTOCOL_MANGLING
+I2C_M_RECV_LEN        = 0x0400  # length will be first received byte
+
+I2C_SLAVE             = 0x0703  # Use this slave address
+I2C_SLAVE_FORCE       = 0x0706  # Use this slave address, even if
+                                # is already in use by a driver!
+I2C_TENBIT            = 0x0704  # 0 for 7 bit addrs, != 0 for 10 bit
+I2C_FUNCS             = 0x0705  # Get the adapter functionality mask
+I2C_RDWR              = 0x0707  # Combined R/W transfer (one STOP only)
+I2C_PEC               = 0x0708  # != 0 to use PEC with SMBus
+I2C_SMBUS             = 0x0720  # SMBus transfer
+
+
+# ctypes versions of I2C structs defined by kernel.
+class i2c_msg(Structure):
+    _fields_ = [
+        ('addr',  c_uint16),
+        ('flags', c_uint16),
+        ('len',   c_uint16),
+        ('buf',   POINTER(c_uint8))
+    ]
+
+class i2c_rdwr_ioctl_data(Structure):
+    _fields_ = [
+        ('msgs',  POINTER(i2c_msg)),
+        ('nmsgs', c_uint32)
+    ]
+
+
+def make_i2c_rdwr_data(messages):
+    """Utility function to create and return an i2c_rdwr_ioctl_data structure
+    populated with a list of specified I2C messages.  The messages parameter
+    should be a list of tuples which represent the individual I2C messages to
+    send in this transaction.  Tuples should contain 4 elements: address value,
+    flags value, buffer length, ctypes c_uint8 pointer to buffer.
+    """
+    # Create message array and populate with provided data.
+    msg_data_type = i2c_msg*len(messages)
+    msg_data = msg_data_type()
+    for i, m in enumerate(messages):
+        msg_data[i].addr  = m[0] & 0x7F
+        msg_data[i].flags = m[1]
+        msg_data[i].len   = m[2]
+        msg_data[i].buf   = m[3]
+    # Now build the data structure.
+    data = i2c_rdwr_ioctl_data()
+    data.msgs  = msg_data
+    data.nmsgs = len(messages)
+    return data
+
+
+# Create an interface that mimics the Python SMBus API.
+class SMBus(object):
+    """I2C interface that mimics the Python SMBus API but is implemented with
+    pure Python calls to ioctl and direct /dev/i2c device access.
+    """
+
+    def __init__(self, bus=None):
+        """Create a new smbus instance.  Bus is an optional parameter that
+        specifies the I2C bus number to use, for example 1 would use device
+        /dev/i2c-1.  If bus is not specified then the open function should be
+        called to open the bus.
+        """
+        self._device = None
+        if bus is not None:
+            self.open(bus)
+
+    def __del__(self):
+        """Clean up any resources used by the SMBus instance."""
+        self.close()
+
+    def __enter__(self):
+        """Context manager enter function."""
+        # Just return this object so it can be used in a with statement, like
+        # with SMBus(1) as bus:
+        #     # do stuff!
+        return self
+
+    def __exit__(self, exc_type, exc_val, exc_tb):
+        """Context manager exit function, ensures resources are cleaned up."""
+        self.close()
+        return False  # Don't suppress exceptions.
+
+    def open(self, bus):
+        """Open the smbus interface on the specified bus."""
+        # Close the device if it's already open.
+        if self._device is not None:
+            self.close()
+        # Try to open the file for the specified bus.  Must turn off buffering
+        # or else Python 3 fails (see: https://bugs.python.org/issue20074)
+        self._device = open('/dev/i2c-{0}'.format(bus), 'r+b', buffering=0)
+        # TODO: Catch IOError and throw a better error message that describes
+        # what's wrong (i.e. I2C may not be enabled or the bus doesn't exist).
+
+    def close(self):
+        """Close the smbus connection.  You cannot make any other function
+        calls on the bus unless open is called!"""
+        if self._device is not None:
+            self._device.close()
+            self._device = None
+
+    def _select_device(self, addr):
+        """Set the address of the device to communicate with on the I2C bus."""
+        ioctl(self._device.fileno(), I2C_SLAVE, addr & 0x7F)
+
+    def read_byte(self, addr):
+        """Read a single byte from the specified device."""
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        self._select_device(addr)
+        return ord(self._device.read(1))
+
+    def read_byte_data(self, addr, cmd):
+        """Read a single byte from the specified cmd register of the device."""
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        # Build ctypes values to marshall between ioctl and Python.
+        reg = c_uint8(cmd)
+        result = c_uint8()
+        # Build ioctl request.
+        request = make_i2c_rdwr_data([
+            (addr, 0, 1, pointer(reg)),             # Write cmd register.
+            (addr, I2C_M_RD, 1, pointer(result))    # Read 1 byte as result.
+        ])
+        # Make ioctl call and return result data.
+        ioctl(self._device.fileno(), I2C_RDWR, request)
+        return result.value
+
+    def read_word_data(self, addr, cmd):
+        """Read a word (2 bytes) from the specified cmd register of the device.
+        Note that this will interpret data using the endianness of the processor
+        running Python (typically little endian)!
+        """
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        # Build ctypes values to marshall between ioctl and Python.
+        reg = c_uint8(cmd)
+        result = c_uint16()
+        # Build ioctl request.
+        request = make_i2c_rdwr_data([
+            (addr, 0, 1, pointer(reg)),             # Write cmd register.
+            (addr, I2C_M_RD, 2, cast(pointer(result), POINTER(c_uint8)))   # Read word (2 bytes).
+        ])
+        # Make ioctl call and return result data.
+        ioctl(self._device.fileno(), I2C_RDWR, request)
+        return result.value
+
+    def read_block_data(self, addr, cmd):
+        """Perform a block read from the specified cmd register of the device.
+        The amount of data read is determined by the first byte send back by
+        the device.  Data is returned as a bytearray.
+        """
+        # TODO: Unfortunately this will require calling the low level I2C
+        # access ioctl to trigger a proper read_block_data.  The amount of data
+        # returned isn't known until the device starts responding so an I2C_RDWR
+        # ioctl won't work.
+        raise NotImplementedError()
+
+    def read_i2c_block_data(self, addr, cmd, len=32):
+        """Perform a read from the specified cmd register of device.  Len number
+        of bytes (default of 32) will be read and returned as a bytearray.
+        """
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        # Build ctypes values to marshall between ioctl and Python.
+        reg = c_uint8(cmd)
+        result = create_string_buffer(len)
+        # Build ioctl request.
+        request = make_i2c_rdwr_data([
+            (addr, 0, 1, pointer(reg)),             # Write cmd register.
+            (addr, I2C_M_RD, len, cast(pointer(result), POINTER(c_uint8)))   # Read data.
+        ])
+        # Make ioctl call and return result data.
+        ioctl(self._device.fileno(), I2C_RDWR, request)
+        return result.value
+
+    def write_quick(self, addr):
+        """Write a single byte to the specified device."""
+        # What a strange function, from the python-smbus source this appears to
+        # just write a single byte that initiates a write to the specified device
+        # address (but writes no data!).  The functionality is duplicated below
+        # but the actual use case for this is unknown.
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        # Build ioctl request.
+        request = make_i2c_rdwr_data([
+            (addr, 0, 0, None),  # Write with no data.
+        ])
+        # Make ioctl call and return result data.
+        ioctl(self._device.fileno(), I2C_RDWR, request)
+
+    def write_byte(self, addr, val):
+        """Write a single byte to the specified device."""
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        self._select_device(addr)
+        data = bytearray(1)
+        data[0] = val & 0xFF
+        self._device.write(data)
+
+    def write_byte_data(self, addr, cmd, val):
+        """Write a byte of data to the specified cmd register of the device.
+        """
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        # Construct a string of data to send with the command register and byte value.
+        data = bytearray(2)
+        data[0] = cmd & 0xFF
+        data[1] = val & 0xFF
+        # Send the data to the device.
+        self._select_device(addr)
+        self._device.write(data)
+
+    def write_word_data(self, addr, cmd, val):
+        """Write a word (2 bytes) of data to the specified cmd register of the
+        device.  Note that this will write the data in the endianness of the
+        processor running Python (typically little endian)!
+        """
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        # Construct a string of data to send with the command register and word value.
+        data = struct.pack('=BH', cmd & 0xFF, val & 0xFFFF)
+        # Send the data to the device.
+        self._select_device(addr)
+        self._device.write(data)
+
+    def write_block_data(self, addr, cmd, vals):
+        """Write a block of data to the specified cmd register of the device.
+        The amount of data to write should be the first byte inside the vals
+        string/bytearray and that count of bytes of data to write should follow
+        it.
+        """
+        # Just use the I2C block data write to write the provided values and
+        # their length as the first byte.
+        data = bytearray(len(vals)+1)
+        data[0] = len(vals) & 0xFF
+        data[1:] = vals[0:]
+        self.write_i2c_block_data(addr, cmd, data)
+
+    def write_i2c_block_data(self, addr, cmd, vals):
+        """Write a buffer of data to the specified cmd register of the device.
+        """
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        assert vals is not None and len(vals) > 0, 'Vals must be a buffer with data!'
+        # Construct a string of data to send, including room for the command register.
+        data = bytearray(len(vals)+1)
+        data[0] = cmd & 0xFF  # Command register at the start.
+        data[1:] = vals[0:]   # Copy in the block data (ugly but necessary to ensure
+                              # the entire write happens in one transaction).
+        # Send the data to the device.
+        self._select_device(addr)
+        self._device.write(data)
+
+    def process_call(self, addr, cmd, val):
+        """Perform a smbus process call by writing a word (2 byte) value to
+        the specified register of the device, and then reading a word of response
+        data (which is returned).
+        """
+        assert self._device is not None, 'Bus must be opened before operations are made against it!'
+        # Build ctypes values to marshall between ioctl and Python.
+        data = create_string_buffer(struct.pack('=BH', cmd, val))
+        result = c_uint16()
+        # Build ioctl request.
+        request = make_i2c_rdwr_data([
+            (addr, 0, 3, cast(pointer(data), POINTER(c_uint8))),          # Write data.
+            (addr, I2C_M_RD, 2, cast(pointer(result), POINTER(c_uint8)))  # Read word (2 bytes).
+        ])
+        # Make ioctl call and return result data.
+        ioctl(self._device.fileno(), I2C_RDWR, request)
+        # Note the python-smbus code appears to have a rather serious bug and
+        # does not return the result value!  This is fixed below by returning it.
+        return result.value

LICENSE

@@ -0,0 +1,21 @@
+The MIT License (MIT)
+
+Copyright (c) 2016 Adafruit Industries
+
+Permission is hereby granted, free of charge, to any person obtaining a copy
+of this software and associated documentation files (the "Software"), to deal
+in the Software without restriction, including without limitation the rights
+to use, copy, modify, merge, publish, distribute, sublicense, and/or sell
+copies of the Software, and to permit persons to whom the Software is
+furnished to do so, subject to the following conditions:
+
+The above copyright notice and this permission notice shall be included in all
+copies or substantial portions of the Software.
+
+THE SOFTWARE IS PROVIDED "AS IS", WITHOUT WARRANTY OF ANY KIND, EXPRESS OR
+IMPLIED, INCLUDING BUT NOT LIMITED TO THE WARRANTIES OF MERCHANTABILITY,
+FITNESS FOR A PARTICULAR PURPOSE AND NONINFRINGEMENT. IN NO EVENT SHALL THE
+AUTHORS OR COPYRIGHT HOLDERS BE LIABLE FOR ANY CLAIM, DAMAGES OR OTHER
+LIABILITY, WHETHER IN AN ACTION OF CONTRACT, TORT OR OTHERWISE, ARISING FROM,
+OUT OF OR IN CONNECTION WITH THE SOFTWARE OR THE USE OR OTHER DEALINGS IN THE
+SOFTWARE.

README.md

@@ -1,2 +1,8 @@
-# Adafruit_Python_PureIO
+# Adafruit Python PureIO
-Pure python (i.e. no native extensions) access to Linux IO including I2C and SPI.  Drop in replacement for smbus and spidev modules.
+
+Pure python (i.e. no native extensions) access to Linux IO including I2C and SPI.  
+Drop in replacement for smbus and spidev modules.
+
+NOTE: This is a work in progress that's not yet ready for public consumption.
+API signatures could change and all APIs are not yet implemented.  Wait for a
+1.x.x series release before depending on this code.

ez_setup.py

@@ -0,0 +1,332 @@
+#!/usr/bin/env python
+"""Bootstrap setuptools installation
+
+To use setuptools in your package's setup.py, include this
+file in the same directory and add this to the top of your setup.py::
+
+    from ez_setup import use_setuptools
+    use_setuptools()
+
+To require a specific version of setuptools, set a download
+mirror, or use an alternate download directory, simply supply
+the appropriate options to ``use_setuptools()``.
+
+This file can also be run as a script to install or upgrade setuptools.
+"""
+import os
+import shutil
+import sys
+import tempfile
+import zipfile
+import optparse
+import subprocess
+import platform
+import textwrap
+import contextlib
+
+from distutils import log
+
+try:
+    from site import USER_SITE
+except ImportError:
+    USER_SITE = None
+
+DEFAULT_VERSION = "3.5.1"
+DEFAULT_URL = "https://pypi.python.org/packages/source/s/setuptools/"
+
+def _python_cmd(*args):
+    """
+    Return True if the command succeeded.
+    """
+    args = (sys.executable,) + args
+    return subprocess.call(args) == 0
+
+
+def _install(archive_filename, install_args=()):
+    with archive_context(archive_filename):
+        # installing
+        log.warn('Installing Setuptools')
+        if not _python_cmd('setup.py', 'install', *install_args):
+            log.warn('Something went wrong during the installation.')
+            log.warn('See the error message above.')
+            # exitcode will be 2
+            return 2
+
+
+def _build_egg(egg, archive_filename, to_dir):
+    with archive_context(archive_filename):
+        # building an egg
+        log.warn('Building a Setuptools egg in %s', to_dir)
+        _python_cmd('setup.py', '-q', 'bdist_egg', '--dist-dir', to_dir)
+    # returning the result
+    log.warn(egg)
+    if not os.path.exists(egg):
+        raise IOError('Could not build the egg.')
+
+
+def get_zip_class():
+    """
+    Supplement ZipFile class to support context manager for Python 2.6
+    """
+    class ContextualZipFile(zipfile.ZipFile):
+        def __enter__(self):
+            return self
+        def __exit__(self, type, value, traceback):
+            self.close
+    return zipfile.ZipFile if hasattr(zipfile.ZipFile, '__exit__') else \
+        ContextualZipFile
+
+
+@contextlib.contextmanager
+def archive_context(filename):
+    # extracting the archive
+    tmpdir = tempfile.mkdtemp()
+    log.warn('Extracting in %s', tmpdir)
+    old_wd = os.getcwd()
+    try:
+        os.chdir(tmpdir)
+        with get_zip_class()(filename) as archive:
+            archive.extractall()
+
+        # going in the directory
+        subdir = os.path.join(tmpdir, os.listdir(tmpdir)[0])
+        os.chdir(subdir)
+        log.warn('Now working in %s', subdir)
+        yield
+
+    finally:
+        os.chdir(old_wd)
+        shutil.rmtree(tmpdir)
+
+
+def _do_download(version, download_base, to_dir, download_delay):
+    egg = os.path.join(to_dir, 'setuptools-%s-py%d.%d.egg'
+                       % (version, sys.version_info[0], sys.version_info[1]))
+    if not os.path.exists(egg):
+        archive = download_setuptools(version, download_base,
+                                      to_dir, download_delay)
+        _build_egg(egg, archive, to_dir)
+    sys.path.insert(0, egg)
+
+    # Remove previously-imported pkg_resources if present (see
+    # https://bitbucket.org/pypa/setuptools/pull-request/7/ for details).
+    if 'pkg_resources' in sys.modules:
+        del sys.modules['pkg_resources']
+
+    import setuptools
+    setuptools.bootstrap_install_from = egg
+
+
+def use_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
+        to_dir=os.curdir, download_delay=15):
+    to_dir = os.path.abspath(to_dir)
+    rep_modules = 'pkg_resources', 'setuptools'
+    imported = set(sys.modules).intersection(rep_modules)
+    try:
+        import pkg_resources
+    except ImportError:
+        return _do_download(version, download_base, to_dir, download_delay)
+    try:
+        pkg_resources.require("setuptools>=" + version)
+        return
+    except pkg_resources.DistributionNotFound:
+        return _do_download(version, download_base, to_dir, download_delay)
+    except pkg_resources.VersionConflict as VC_err:
+        if imported:
+            msg = textwrap.dedent("""
+                The required version of setuptools (>={version}) is not available,
+                and can't be installed while this script is running. Please
+                install a more recent version first, using
+                'easy_install -U setuptools'.
+
+                (Currently using {VC_err.args[0]!r})
+                """).format(VC_err=VC_err, version=version)
+            sys.stderr.write(msg)
+            sys.exit(2)
+
+        # otherwise, reload ok
+        del pkg_resources, sys.modules['pkg_resources']
+        return _do_download(version, download_base, to_dir, download_delay)
+
+def _clean_check(cmd, target):
+    """
+    Run the command to download target. If the command fails, clean up before
+    re-raising the error.
+    """
+    try:
+        subprocess.check_call(cmd)
+    except subprocess.CalledProcessError:
+        if os.access(target, os.F_OK):
+            os.unlink(target)
+        raise
+
+def download_file_powershell(url, target):
+    """
+    Download the file at url to target using Powershell (which will validate
+    trust). Raise an exception if the command cannot complete.
+    """
+    target = os.path.abspath(target)
+    cmd = [
+        'powershell',
+        '-Command',
+        "(new-object System.Net.WebClient).DownloadFile(%(url)r, %(target)r)" % vars(),
+    ]
+    _clean_check(cmd, target)
+
+def has_powershell():
+    if platform.system() != 'Windows':
+        return False
+    cmd = ['powershell', '-Command', 'echo test']
+    devnull = open(os.path.devnull, 'wb')
+    try:
+        try:
+            subprocess.check_call(cmd, stdout=devnull, stderr=devnull)
+        except Exception:
+            return False
+    finally:
+        devnull.close()
+    return True
+
+download_file_powershell.viable = has_powershell
+
+def download_file_curl(url, target):
+    cmd = ['curl', url, '--silent', '--output', target]
+    _clean_check(cmd, target)
+
+def has_curl():
+    cmd = ['curl', '--version']
+    devnull = open(os.path.devnull, 'wb')
+    try:
+        try:
+            subprocess.check_call(cmd, stdout=devnull, stderr=devnull)
+        except Exception:
+            return False
+    finally:
+        devnull.close()
+    return True
+
+download_file_curl.viable = has_curl
+
+def download_file_wget(url, target):
+    cmd = ['wget', url, '--quiet', '--output-document', target]
+    _clean_check(cmd, target)
+
+def has_wget():
+    cmd = ['wget', '--version']
+    devnull = open(os.path.devnull, 'wb')
+    try:
+        try:
+            subprocess.check_call(cmd, stdout=devnull, stderr=devnull)
+        except Exception:
+            return False
+    finally:
+        devnull.close()
+    return True
+
+download_file_wget.viable = has_wget
+
+def download_file_insecure(url, target):
+    """
+    Use Python to download the file, even though it cannot authenticate the
+    connection.
+    """
+    try:
+        from urllib.request import urlopen
+    except ImportError:
+        from urllib2 import urlopen
+    src = dst = None
+    try:
+        src = urlopen(url)
+        # Read/write all in one block, so we don't create a corrupt file
+        # if the download is interrupted.
+        data = src.read()
+        dst = open(target, "wb")
+        dst.write(data)
+    finally:
+        if src:
+            src.close()
+        if dst:
+            dst.close()
+
+download_file_insecure.viable = lambda: True
+
+def get_best_downloader():
+    downloaders = [
+        download_file_powershell,
+        download_file_curl,
+        download_file_wget,
+        download_file_insecure,
+    ]
+
+    for dl in downloaders:
+        if dl.viable():
+            return dl
+
+def download_setuptools(version=DEFAULT_VERSION, download_base=DEFAULT_URL,
+        to_dir=os.curdir, delay=15, downloader_factory=get_best_downloader):
+    """
+    Download setuptools from a specified location and return its filename
+
+    `version` should be a valid setuptools version number that is available
+    as an egg for download under the `download_base` URL (which should end
+    with a '/'). `to_dir` is the directory where the egg will be downloaded.
+    `delay` is the number of seconds to pause before an actual download
+    attempt.
+
+    ``downloader_factory`` should be a function taking no arguments and
+    returning a function for downloading a URL to a target.
+    """
+    # making sure we use the absolute path
+    to_dir = os.path.abspath(to_dir)
+    zip_name = "setuptools-%s.zip" % version
+    url = download_base + zip_name
+    saveto = os.path.join(to_dir, zip_name)
+    if not os.path.exists(saveto):  # Avoid repeated downloads
+        log.warn("Downloading %s", url)
+        downloader = downloader_factory()
+        downloader(url, saveto)
+    return os.path.realpath(saveto)
+
+def _build_install_args(options):
+    """
+    Build the arguments to 'python setup.py install' on the setuptools package
+    """
+    return ['--user'] if options.user_install else []
+
+def _parse_args():
+    """
+    Parse the command line for options
+    """
+    parser = optparse.OptionParser()
+    parser.add_option(
+        '--user', dest='user_install', action='store_true', default=False,
+        help='install in user site package (requires Python 2.6 or later)')
+    parser.add_option(
+        '--download-base', dest='download_base', metavar="URL",
+        default=DEFAULT_URL,
+        help='alternative URL from where to download the setuptools package')
+    parser.add_option(
+        '--insecure', dest='downloader_factory', action='store_const',
+        const=lambda: download_file_insecure, default=get_best_downloader,
+        help='Use internal, non-validating downloader'
+    )
+    parser.add_option(
+        '--version', help="Specify which version to download",
+        default=DEFAULT_VERSION,
+    )
+    options, args = parser.parse_args()
+    # positional arguments are ignored
+    return options
+
+def main():
+    """Install or upgrade setuptools and EasyInstall"""
+    options = _parse_args()
+    archive = download_setuptools(
+        version=options.version,
+        download_base=options.download_base,
+        downloader_factory=options.downloader_factory,
+    )
+    return _install(archive, _build_install_args(options))
+
+if __name__ == '__main__':
+    sys.exit(main())

setup.py

@@ -0,0 +1,21 @@
+from ez_setup import use_setuptools
+use_setuptools()
+from setuptools import setup, find_packages
+
+classifiers = ['Development Status :: 4 - Beta',
+               'Operating System :: POSIX :: Linux',
+               'License :: OSI Approved :: MIT License',
+               'Intended Audience :: Developers',
+               'Programming Language :: Python :: 2.7',
+               'Programming Language :: Python :: 3',
+               'Topic :: Software Development',
+               'Topic :: System :: Hardware']
+
+setup(name              = 'Adafruit_PureIO',
+      version           = '0.0.1',
+      author            = 'Tony DiCola',
+      author_email      = 'tdicola@adafruit.com',
+      description       = 'Pure python (i.e. no native extensions) access to Linux IO including I2C and SPI.  Drop in replacement for smbus and spidev modules.',
+      license           = 'MIT',
+      classifiers       = classifiers,
+      packages          = find_packages())

tests/test_I2C.py

@@ -0,0 +1,49 @@
+# Basic smbus test.  This is pretty ugly and meant to be run against a ADS1x15
+# and some output inspected by a Saleae logic analyzer.  TODO: Refactor into
+# something that can test without hardware?
+import binascii
+
+import Adafruit_PureIO.smbus as smbus
+
+
+DEVICE_ADDR = 0x48
+REGISTER    = 0x01
+
+
+# Test open and close.
+i2c = smbus.SMBus()
+i2c.open(1)
+val = i2c.read_byte(DEVICE_ADDR)
+print('read_byte from 0x{0:0X}: 0x{1:0X}'.format(REGISTER, val))
+i2c.close()
+
+# Test initializer open.
+i2c = smbus.SMBus(1)
+val = i2c.read_byte(DEVICE_ADDR)
+print('read_byte from 0x{0:0X}: 0x{1:0X}'.format(REGISTER, val))
+i2c.close()
+
+# Test various data reads.
+with smbus.SMBus(1) as i2c:
+    val = i2c.read_byte(DEVICE_ADDR)
+    print('read_byte from 0x{0:0X}: 0x{1:0X}'.format(REGISTER, val))
+    val = i2c.read_byte_data(DEVICE_ADDR, REGISTER)
+    print('read_byte_data from 0x{0:0X}: 0x{1:0X}'.format(REGISTER, val))
+    val = i2c.read_word_data(DEVICE_ADDR, REGISTER)
+    print('read_word_data from 0x{0:0X}: 0x{1:04X}'.format(REGISTER, val))
+    val = i2c.read_i2c_block_data(DEVICE_ADDR, REGISTER, 2)
+    print('read_i2c_block_data from 0x{0:0X}: 0x{1}'.format(REGISTER, binascii.hexlify(val)))
+
+# Test various data writes.
+with smbus.SMBus(1) as i2c:
+    i2c.write_byte(DEVICE_ADDR, REGISTER)
+    i2c.write_byte_data(DEVICE_ADDR, REGISTER, 0x85)
+    i2c.write_word_data(DEVICE_ADDR, REGISTER, 0x8385)
+    i2c.write_i2c_block_data(DEVICE_ADDR, REGISTER, [0x85, 0x83])
+    #i2c.write_block_data(DEVICE_ADDR, REGISTER, [0x85, 0x83])
+    i2c.write_quick(DEVICE_ADDR)
+
+# Process call test.
+with smbus.SMBus(1) as i2c:
+    val = i2c.process_call(DEVICE_ADDR, REGISTER, 0x8385)
+    print('process_call from 0x{0:0X}: 0x{1:04X}'.format(REGISTER, val))