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MCP23017 python 3 library with interrupts / smbus python 3

Install smbus for python 3 on the Raspberry Pi

sudo apt-get update

sudo apt-get install python3-dev gcc

wget http://ftp.de.debian.org/debian/pool/main/i/i2c-tools/i2c-tools_3.1.1.orig.tar.bz2

tar -xf i2c-tools_3.1.1.orig.tar.bz2

cd i2c-tools-3.1.1/py-smbus

cp smbusmodule.c smbusmodule.c.orig # make backup

Use the code below to replace the contents of smbusmodule.c

Download a 2.x version of lm-sensors from http://lm-sensors.org/wiki/Download and unpack it. (I had some issues trying to use tar or Xarchiver on my Pi, but managed just fine using 7-Zip on a PC).

Copy ./lm_sensors-2.10.8/kernel/include/i2c-dev.h to the directory containing your modified smbusmodule.c, such as ./i2c-tools-3.1.1/py-smbus/

Run the following commands from within the ./i2c-tools-3.1.1/py-smbus directory

python3 setup.py build

sudo python3 setup.py install

/*
 * smbusmodule.c - Python bindings for Linux SMBus access through i2c-dev
 * Copyright (C) 2005-2007 Mark M. Hoffman <mhoffman@xxxxxxxxxxxxx>
 *
 * This program is free software; you can redistribute it and/or modify
 * it under the terms of the GNU General Public License as published by
 * the Free Software Foundation; version 2 of the License.
 *
 * This program is distributed in the hope that it will be useful,
 * but WITHOUT ANY WARRANTY; without even the implied warranty of
 * MERCHANTABILITY or FITNESS FOR A PARTICULAR PURPOSE.  See the
 * GNU General Public License for more details.
 *
 * You should have received a copy of the GNU General Public License
 * along with this program; if not, write to the Free Software
 * Foundation, Inc., 59 Temple Place - Suite 330, Boston, MA  02111-1307, USA.
 */

#include <Python.h>
#include "structmember.h"
#include <stdlib.h>
#include <stdio.h>
#include <fcntl.h>
#include "i2c-dev.h"

/*
** These are required to build this module against Linux older than 2.6.23.
*/
#ifndef I2C_SMBUS_I2C_BLOCK_BROKEN
#undef I2C_SMBUS_I2C_BLOCK_DATA
#define I2C_SMBUS_I2C_BLOCK_BROKEN  6
#define I2C_SMBUS_I2C_BLOCK_DATA    8
#endif

/*yDoc_STRVAR(SMBus_module_doc,
    "This module defines an object type that allows SMBus transactions\n"
    "on hosts running the Linux kernel.  The host kernel must have I2C\n"
    "support, I2C device interface support, and a bus adapter driver.\n"
    "All of these can be either built-in to the kernel, or loaded from\n"
    "modules.\n"
    "\n"
    "Because the I2C device interface is opened R/W, users of this\n"
    "module usually must have root permissions.\n");
*/

typedef struct {
    PyObject_HEAD

    int fd;     /* open file descriptor: /dev/i2c-?, or -1 */
    int addr;   /* current client SMBus address */
    int pec;    /* !0 => Packet Error Codes enabled */
} SMBus;

static PyObject *
SMBus_new(PyTypeObject *type, PyObject *args, PyObject *kwds)
{
    SMBus *self;

    if ((self = (SMBus *)type->tp_alloc(type, 0)) == NULL)
        return NULL;

    self->fd = -1;
    self->addr = -1;
    self->pec = 0;

    return (PyObject *)self;
}

PyDoc_STRVAR(SMBus_close_doc,
    "close()\n\n"
    "Disconnects the object from the bus.\n");

static PyObject *
SMBus_close(SMBus *self)
{
    if ((self->fd != -1) && (close(self->fd) == -1)) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    self->fd = -1;
    self->addr = -1;
    self->pec = 0;

    Py_INCREF(Py_None);
    return Py_None;
}

static void
SMBus_dealloc(SMBus *self)
{
    PyObject *ref = SMBus_close(self);
    Py_XDECREF(ref);

    /*old python 2.7 declaration */
    /*self->ob_type->tp_free((PyObject *)self);*/
    Py_TYPE(self)->tp_free((PyObject*)self);
}

#define MAXPATH 16

PyDoc_STRVAR(SMBus_open_doc,
    "open(bus)\n\n"
    "Connects the object to the specified SMBus.\n");

static PyObject *
SMBus_open(SMBus *self, PyObject *args, PyObject *kwds)
{
    int bus;
    char path[MAXPATH];

    static char *kwlist[] = {"bus", NULL};

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "i:open", kwlist, &bus))
        return NULL;

    if (snprintf(path, MAXPATH, "/dev/i2c-%d", bus) >= MAXPATH) {
        PyErr_SetString(PyExc_OverflowError,
            "Bus number is invalid.");
        return NULL;
    }

    if ((self->fd = open(path, O_RDWR, 0)) == -1) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

static int
SMBus_init(SMBus *self, PyObject *args, PyObject *kwds)
{
    int bus = -1;

    static char *kwlist[] = {"bus", NULL};

    if (!PyArg_ParseTupleAndKeywords(args, kwds, "|i:__init__",
            kwlist, &bus))
        return -1;

    if (bus >= 0) {
        SMBus_open(self, args, kwds);
        if (PyErr_Occurred())
            return -1;
    }

    return 0;
}

/*
 * private helper function, 0 => success, !0 => error
 */
static int
SMBus_set_addr(SMBus *self, int addr)
{
    int ret = 0;

    if (self->addr != addr) {
        ret = ioctl(self->fd, I2C_SLAVE, addr);
        self->addr = addr;
    }

    return ret;
}

#define SMBus_SET_ADDR(self, addr) do { \
    if (SMBus_set_addr(self, addr)) { \
        PyErr_SetFromErrno(PyExc_IOError); \
        return NULL; \
    } \
} while(0)

PyDoc_STRVAR(SMBus_write_quick_doc,
    "write_quick(addr)\n\n"
    "Perform SMBus Quick transaction.\n");

static PyObject *
SMBus_write_quick(SMBus *self, PyObject *args)
{
    int addr;
    __s32 result;

    if (!PyArg_ParseTuple(args, "i:write_quick", &addr))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    if ((result = i2c_smbus_write_quick(self->fd, I2C_SMBUS_WRITE))) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

PyDoc_STRVAR(SMBus_read_byte_doc,
    "read_byte(addr) -> result\n\n"
    "Perform SMBus Read Byte transaction.\n");

static PyObject *
SMBus_read_byte(SMBus *self, PyObject *args)
{
    int addr;
    __s32 result;

    if (!PyArg_ParseTuple(args, "i:read_byte", &addr))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    if ((result = i2c_smbus_read_byte(self->fd)) == -1) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    return Py_BuildValue("l", (long)result);
}

PyDoc_STRVAR(SMBus_write_byte_doc,
    "write_byte(addr, val)\n\n"
    "Perform SMBus Write Byte transaction.\n");

static PyObject *
SMBus_write_byte(SMBus *self, PyObject *args)
{
    int addr, val;
    __s32 result;

    if (!PyArg_ParseTuple(args, "ii:write_byte", &addr, &val))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    if ((result = i2c_smbus_write_byte(self->fd, (__u8)val)) == -1) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

PyDoc_STRVAR(SMBus_read_byte_data_doc,
    "read_byte_data(addr, cmd) -> result\n\n"
    "Perform SMBus Read Byte Data transaction.\n");

static PyObject *
SMBus_read_byte_data(SMBus *self, PyObject *args)
{
    int addr, cmd;
    __s32 result;

    if (!PyArg_ParseTuple(args, "ii:read_byte_data", &addr, &cmd))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    if ((result = i2c_smbus_read_byte_data(self->fd, (__u8)cmd)) == -1) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    return Py_BuildValue("l", (long)result);
}

PyDoc_STRVAR(SMBus_write_byte_data_doc,
    "write_byte_data(addr, cmd, val)\n\n"
    "Perform SMBus Write Byte Data transaction.\n");

static PyObject *
SMBus_write_byte_data(SMBus *self, PyObject *args)
{
    int addr, cmd, val;
    __s32 result;

    if (!PyArg_ParseTuple(args, "iii:write_byte_data", &addr, &cmd, &val))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    if ((result = i2c_smbus_write_byte_data(self->fd,
                (__u8)cmd, (__u8)val)) == -1) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

PyDoc_STRVAR(SMBus_read_word_data_doc,
    "read_word_data(addr, cmd) -> result\n\n"
    "Perform SMBus Read Word Data transaction.\n");

static PyObject *
SMBus_read_word_data(SMBus *self, PyObject *args)
{
    int addr, cmd;
    __s32 result;

    if (!PyArg_ParseTuple(args, "ii:read_word_data", &addr, &cmd))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    if ((result = i2c_smbus_read_word_data(self->fd, (__u8)cmd)) == -1) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    return Py_BuildValue("l", (long)result);
}

PyDoc_STRVAR(SMBus_write_word_data_doc,
    "write_word_data(addr, cmd, val)\n\n"
    "Perform SMBus Write Word Data transaction.\n");

static PyObject *
SMBus_write_word_data(SMBus *self, PyObject *args)
{
    int addr, cmd, val;
    __s32 result;

    if (!PyArg_ParseTuple(args, "iii:write_word_data", &addr, &cmd, &val))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    if ((result = i2c_smbus_write_word_data(self->fd,
                (__u8)cmd, (__u16)val)) == -1) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

PyDoc_STRVAR(SMBus_process_call_doc,
    "process_call(addr, cmd, val)\n\n"
    "Perform SMBus Process Call transaction.\n");

static PyObject *
SMBus_process_call(SMBus *self, PyObject *args)
{
    int addr, cmd, val;
    __s32 result;

    if (!PyArg_ParseTuple(args, "iii:process_call", &addr, &cmd, &val))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    if ((result = i2c_smbus_process_call(self->fd,
                (__u8)cmd, (__u16)val)) == -1) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

/*
 * private helper function; returns a new list of integers
 */
static PyObject *
SMBus_buf_to_list(__u8 const *buf, int len)
{
    PyObject *list = PyList_New(len);
    int ii;

    if (list == NULL)
        return NULL;

    for (ii = 0; ii < len; ii++) {
        PyObject *val = Py_BuildValue("l", (long)buf[ii]);
        PyList_SET_ITEM(list, ii, val);
    }
    return list;
}

PyDoc_STRVAR(SMBus_read_block_data_doc,
    "read_block_data(addr, cmd) -> results\n\n"
    "Perform SMBus Read Block Data transaction.\n");

static PyObject *
SMBus_read_block_data(SMBus *self, PyObject *args)
{
    int addr, cmd;
    union i2c_smbus_data data;

    if (!PyArg_ParseTuple(args, "ii:read_block_data", &addr, &cmd))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    /* save a bit of code by calling the access function directly */
    if (i2c_smbus_access(self->fd, I2C_SMBUS_READ, (__u8)cmd,
                I2C_SMBUS_BLOCK_DATA, &data)) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    /* first byte of the block contains (remaining) data length */
    return SMBus_buf_to_list(&data.block[1], data.block[0]);
}

/*
 * private helper function: convert an integer list to union i2c_smbus_data
 */
static int
SMBus_list_to_data(PyObject *list, union i2c_smbus_data *data)
{
    static char *msg = "Third argument must be a list of at least one, "
                "but not more than 32 integers";
    int ii, len;

    if (!PyList_Check(list)) {
        PyErr_SetString(PyExc_TypeError, msg);
        return 0; /* fail */
    }

    if ((len = PyList_GET_SIZE(list)) > 32) {
        PyErr_SetString(PyExc_OverflowError, msg);
        return 0; /* fail */
    }

    /* first byte is the length */
    data->block[0] = (__u8)len;

    for (ii = 0; ii < len; ii++) {
        PyObject *val = PyList_GET_ITEM(list, ii);
        if (!PyLong_Check(val)) {
            PyErr_SetString(PyExc_TypeError, msg);
            return 0; /* fail */
        }
        data->block[ii+1] = (__u8)PyLong_AS_LONG(val);
    }

    return 1; /* success */
}

PyDoc_STRVAR(SMBus_write_block_data_doc,
    "write_block_data(addr, cmd, [vals])\n\n"
    "Perform SMBus Write Block Data transaction.\n");

static PyObject *
SMBus_write_block_data(SMBus *self, PyObject *args)
{
    int addr, cmd;
    union i2c_smbus_data data;

    if (!PyArg_ParseTuple(args, "iiO&:write_block_data", &addr, &cmd,
                SMBus_list_to_data, &data))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    /* save a bit of code by calling the access function directly */
    if (i2c_smbus_access(self->fd, I2C_SMBUS_WRITE, (__u8)cmd,
                I2C_SMBUS_BLOCK_DATA, &data)) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

PyDoc_STRVAR(SMBus_block_process_call_doc,
    "block_process_call(addr, cmd, [vals]) -> results\n\n"
    "Perform SMBus Block Process Call transaction.\n");

static PyObject *
SMBus_block_process_call(SMBus *self, PyObject *args)
{
    int addr, cmd;
    union i2c_smbus_data data;

    if (!PyArg_ParseTuple(args, "iiO&:block_process_call", &addr, &cmd,
            SMBus_list_to_data, &data))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    /* save a bit of code by calling the access function directly */
    if (i2c_smbus_access(self->fd, I2C_SMBUS_WRITE, (__u8)cmd,
                I2C_SMBUS_BLOCK_PROC_CALL, &data)) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    /* first byte of the block contains (remaining) data length */
    return SMBus_buf_to_list(&data.block[1], data.block[0]);
}

PyDoc_STRVAR(SMBus_read_i2c_block_data_doc,
    "read_i2c_block_data(addr, cmd, len=32) -> results\n\n"
    "Perform I2C Block Read transaction.\n");

static PyObject *
SMBus_read_i2c_block_data(SMBus *self, PyObject *args)
{
    int addr, cmd, len=32;
    union i2c_smbus_data data;

    if (!PyArg_ParseTuple(args, "ii|i:read_i2c_block_data", &addr, &cmd,
            &len))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    data.block[0] = len;
    /* save a bit of code by calling the access function directly */
    if (i2c_smbus_access(self->fd, I2C_SMBUS_READ, (__u8)cmd,
                len == 32 ? I2C_SMBUS_I2C_BLOCK_BROKEN:
                I2C_SMBUS_I2C_BLOCK_DATA, &data)) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    /* first byte of the block contains (remaining) data length */
    return SMBus_buf_to_list(&data.block[1], data.block[0]);
}

PyDoc_STRVAR(SMBus_write_i2c_block_data_doc,
    "write_i2c_block_data(addr, cmd, [vals])\n\n"
    "Perform I2C Block Write transaction.\n");

static PyObject *
SMBus_write_i2c_block_data(SMBus *self, PyObject *args)
{
    int addr, cmd;
    union i2c_smbus_data data;

    if (!PyArg_ParseTuple(args, "iiO&:write_i2c_block_data", &addr, &cmd,
            SMBus_list_to_data, &data))
        return NULL;

    SMBus_SET_ADDR(self, addr);

    /* save a bit of code by calling the access function directly */
    if (i2c_smbus_access(self->fd, I2C_SMBUS_WRITE, (__u8)cmd,
                I2C_SMBUS_I2C_BLOCK_BROKEN, &data)) {
        PyErr_SetFromErrno(PyExc_IOError);
        return NULL;
    }

    Py_INCREF(Py_None);
    return Py_None;
}

PyDoc_STRVAR(SMBus_type_doc,
    "SMBus([bus]) -> SMBus\n\n"
    "Return a new SMBus object that is (optionally) connected to the\n"
    "specified I2C device interface.\n");

static PyMethodDef SMBus_methods[] = {
    {"open", (PyCFunction)SMBus_open, METH_VARARGS | METH_KEYWORDS,
        SMBus_open_doc},
    {"close", (PyCFunction)SMBus_close, METH_NOARGS,
        SMBus_close_doc},
    {"write_quick", (PyCFunction)SMBus_write_quick, METH_VARARGS,
        SMBus_write_quick_doc},
    {"read_byte", (PyCFunction)SMBus_read_byte, METH_VARARGS,
        SMBus_read_byte_doc},
    {"write_byte", (PyCFunction)SMBus_write_byte, METH_VARARGS,
        SMBus_write_byte_doc},
    {"read_byte_data", (PyCFunction)SMBus_read_byte_data, METH_VARARGS,
        SMBus_read_byte_data_doc},
    {"write_byte_data", (PyCFunction)SMBus_write_byte_data, METH_VARARGS,
        SMBus_write_byte_data_doc},
    {"read_word_data", (PyCFunction)SMBus_read_word_data, METH_VARARGS,
        SMBus_read_word_data_doc},
    {"write_word_data", (PyCFunction)SMBus_write_word_data, METH_VARARGS,
        SMBus_write_word_data_doc},
    {"process_call", (PyCFunction)SMBus_process_call, METH_VARARGS,
        SMBus_process_call_doc},
    {"read_block_data", (PyCFunction)SMBus_read_block_data, METH_VARARGS,
        SMBus_read_block_data_doc},
    {"write_block_data", (PyCFunction)SMBus_write_block_data, METH_VARARGS,
        SMBus_write_block_data_doc},
    {"block_process_call", (PyCFunction)SMBus_block_process_call,
        METH_VARARGS, SMBus_block_process_call_doc},
    {"read_i2c_block_data", (PyCFunction)SMBus_read_i2c_block_data,
        METH_VARARGS, SMBus_read_i2c_block_data_doc},
    {"write_i2c_block_data", (PyCFunction)SMBus_write_i2c_block_data,
        METH_VARARGS, SMBus_write_i2c_block_data_doc},
    {NULL},
};

static PyObject *
SMBus_get_pec(SMBus *self, void *closure)
{
    PyObject *result = self->pec ? Py_True : Py_False;
    Py_INCREF(result);
    return result;
}

static int
SMBus_set_pec(SMBus *self, PyObject *val, void *closure)
{
    int pec;

    pec = PyObject_IsTrue(val);

    if (val == NULL) {
        PyErr_SetString(PyExc_TypeError,
            "Cannot delete attribute");
        return -1;
    }
    else if (pec == -1) {
        PyErr_SetString(PyExc_TypeError,
            "The pec attribute must be a boolean.");
        return -1;
    }

    if (self->pec != pec) {
        if (ioctl(self->fd, I2C_PEC, pec)) {
            PyErr_SetFromErrno(PyExc_IOError);
            return -1;
        }
        self->pec = pec;
    }

    return 0;
}

static PyGetSetDef SMBus_getset[] = {
    {"pec", (getter)SMBus_get_pec, (setter)SMBus_set_pec,
            "True if Packet Error Codes (PEC) are enabled"},
    {NULL},
};

/* old Python 2.7 declaration */
static PyTypeObject SMBus_type = {
/*tatic struct PyModuleDef SMBus_type = {*/
    /* old Python 2.7 declaration */
    /* PyObject_HEAD_INIT(NULL) */
    /*0,                 ob_size */
    PyVarObject_HEAD_INIT(NULL, 0)
    "SMBus",            /* tp_name */
    sizeof(SMBus),      /* tp_basicsize */
    0,                  /* tp_itemsize */
    (destructor)SMBus_dealloc,  /* tp_dealloc */
    0,              /* tp_print */
    0,              /* tp_getattr */
    0,              /* tp_setattr */
    0,              /* tp_compare */
    0,              /* tp_repr */
    0,              /* tp_as_number */
    0,              /* tp_as_sequence */
    0,              /* tp_as_mapping */
    0,              /* tp_hash */
    0,              /* tp_call */
    0,              /* tp_str */
    0,              /* tp_getattro */
    0,              /* tp_setattro */
    0,              /* tp_as_buffer */
    Py_TPFLAGS_DEFAULT, /* tp_flags */
    SMBus_type_doc,     /* tp_doc */
    0,              /* tp_traverse */
    0,              /* tp_clear */
    0,              /* tp_richcompare */
    0,              /* tp_weaklistoffset */
    0,              /* tp_iter */
    0,              /* tp_iternext */
    SMBus_methods,  /* tp_methods */
    0,              /* tp_members */
    SMBus_getset,   /* tp_getset */
    0,              /* tp_base */
    0,              /* tp_dict */
    0,              /* tp_descr_get */
    0,              /* tp_descr_set */
    0,              /* tp_dictoffset */
    (initproc)SMBus_init,   /* tp_init */
    0,              /* tp_alloc */
    SMBus_new,      /* tp_new */
};

/*static PyMethodDef SMBus_module_methods[] = {
    {NULL}
};*/

static struct PyModuleDef SMBusModule = {
        PyModuleDef_HEAD_INIT,
        "SMBus",     /* m_name */
        "This module defines an object type that allows SMBus transactions\n"
        "on hosts running the Linux kernel.  The host kernel must have I2C\n"
        "support, I2C device interface support, and a bus adapter driver.\n"
        "All of these can be either built-in to the kernel, or loaded from\n"
        "modules.\n"
        "\n"
        "Because the I2C device interface is opened R/W, users of this\n"
        "module usually must have root permissions.\n",  /* m_doc */
        -1,                  /* m_size */
        NULL,    /* m_methods */
        NULL,                /* m_reload */
        NULL,                /* m_traverse */
        NULL,                /* m_clear */
        NULL,                /* m_free */
    };

#ifndef PyMODINIT_FUNC  /* declarations for DLL import/export */
#define PyMODINIT_FUNC void
#endif
PyMODINIT_FUNC
PyInit_smbus(void)
{
    PyObject* m;

    if (PyType_Ready(&SMBus_type) < 0)
        return NULL;

    /* old Python 2.7 declaration */
    /*m = Py_InitModule3("smbus", SMBus_module_methods, SMBus_module_doc);*/
    m = PyModule_Create(&SMBusModule);

    if (m == NULL)
        return NULL;

    Py_INCREF(&SMBus_type);
    PyModule_AddObject(m, "SMBus", (PyObject *)&SMBus_type);

    return m;
}

Updated