spi.c

/* SPI testing utility (see copyright beow)
 *	adapted for use in Python
 * 	by Louis Thiery
 * 	Lots more flexibility and cleanup by Connor Wolf (imaginaryindustries.com)
 *
 * compile for Python using: "python setup.py build"
 * compiled module will be in "./build/lib.linux-armv6l-2.7/spi.so"
 *
 * SPI testing utility (using spidev driver)
 *
 * Copyright (c) 2007  MontaVista Software, Inc.
 * Copyright (c) 2007  Anton Vorontsov <avorontsov@ru.mvista.com>
 *
 * 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; either version 2 of the License.
 *
 */

#include <Python.h>
#include <stdint.h>
#include <unistd.h>
#include <stdio.h>
#include <stdlib.h>
#include <getopt.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <linux/types.h>
#include <linux/spi/spidev.h>

static void pabort(const char *s)
{
	perror(s);
	abort();
}

static const char *device = "/dev/spidev0.0";
static uint8_t mode;
static uint8_t bits = 8;
static uint32_t speed = 500000;
static uint16_t delay;

int ret = 0;
int fd;


static PyObject* openSPI(PyObject *self, PyObject *args, PyObject *kwargs)
{

	static char* kwlist[] = {"device", "mode", "bits", "speed", "delay", NULL};

	// Adding some sort of mode parsing would probably be a nice idea for the future, so you don't have to specify it as a bitfield
	// stuffed into an int.
	// For the moment the default mode ("0"), will probably work for 99% of people who need a SPI interface, so I'm not working on that
	//


	if (!PyArg_ParseTupleAndKeywords(args, kwargs, "|siiii:keywords", kwlist, &device, &mode, &bits, &speed, &delay))
		return NULL;
	// It's not clearly documented, but it seems that PyArg_ParseTupleAndKeywords basically only modifies the values passed to it if the
	// keyword pertaining to that value is passed to the function. As such, the defaults specified by the variable definition are used
	// unless you pass a kwd argument.
	// Note that there isn't any proper bounds-checking, so if you pass a value that exceeds the variable size, it's just truncated before
	// being stuffed into  the avasilable space. For example, passing a bits-per-word of 500 gets truncated to 244. Unfortunately, the
	// PyArg_ParseTupleAndKeywords function only seems to support ints of 32 bits.

	PyErr_Clear();

	// printf("Mode: %i, Bits: %i, Speed: %i, Delay: %i\n", mode, bits, speed, delay);



	fd = open(device, O_RDWR);
	if (fd < 0)
		pabort("can't open device");

	/*
	 * Setup SPI mode
	 */
	ret = ioctl(fd, SPI_IOC_WR_MODE, &mode);
	if (ret == -1)
		pabort("can't set spi mode");

	ret = ioctl(fd, SPI_IOC_RD_MODE, &mode);
	if (ret == -1)
		pabort("can't get spi mode");

	/*
	 * bits per word
	 */
	ret = ioctl(fd, SPI_IOC_WR_BITS_PER_WORD, &bits);
	if (ret == -1)
		pabort("can't set bits per word");

	ret = ioctl(fd, SPI_IOC_RD_BITS_PER_WORD, &bits);
	if (ret == -1)
		pabort("can't get bits per word");

	/*
	 * max speed hz
	 */
	ret = ioctl(fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed);
	if (ret == -1)
		pabort("can't set max speed hz");

	ret = ioctl(fd, SPI_IOC_RD_MAX_SPEED_HZ, &speed);
	if (ret == -1)
		pabort("can't get max speed hz");

	// Stuff the various initilization parameters into a dict, and return that.
	// Note that the returned values may not be completely real. It seems that, at least for the speed value,
	// the hardware only has several possible settings (250000, 500000, 1000000, etc...) Strangely enough, the
	// ioctl for setting the speed *returns the speed you specify*. However, the hardware seems to default to the
	// closest avalable value *below* the specified rate. (i.e. you will never get a speed faster then you spec),
	// but you may get a slower value.

	//It would probably be a good idea to bin-down the passed arguement to the available values, and return
	// that.

	PyObject* retDict;
	retDict = PyDict_New();

#if PY_MAJOR_VERSION >= 3
	PyDict_SetItem(retDict, PyBytes_FromString("mode"), PyLong_FromLong((long)mode));
	PyDict_SetItem(retDict, PyBytes_FromString("bits"), PyLong_FromLong((long)bits));
	PyDict_SetItem(retDict, PyBytes_FromString("speed"), PyLong_FromLong((long)speed));
	PyDict_SetItem(retDict, PyBytes_FromString("delay"), PyLong_FromLong((long)delay));
#else
	PyDict_SetItem(retDict, PyString_FromString("mode"), PyInt_FromLong((long)mode));
	PyDict_SetItem(retDict, PyString_FromString("bits"), PyInt_FromLong((long)bits));
	PyDict_SetItem(retDict, PyString_FromString("speed"), PyInt_FromLong((long)speed));
	PyDict_SetItem(retDict, PyString_FromString("delay"), PyInt_FromLong((long)delay));
#endif


	return retDict;
}



static PyObject* transfer(PyObject* self, PyObject* arg)
{
	PyObject* transferTuple;

	if(!PyArg_ParseTuple(arg, "O", &transferTuple))		// "O" - Gets non-NULL borrowed reference to Python argument.
		return NULL;					// As far as I can tell, it's mostly just copying arg[0] into transferTuple
								// and making sure at least one arg has been passed (I think)

	if(!PyTuple_Check(transferTuple))			// The only argument we support is a single tuple.
		pabort("Only accepts a single tuple as an argument\n");


	uint32_t tupleSize = PyTuple_Size(transferTuple);

	uint8_t tx[tupleSize];
	uint8_t rx[tupleSize];
	PyObject* tempItem;

	uint16_t i=0;

	while(i < tupleSize)
	{
		tempItem = PyTuple_GetItem(transferTuple, i);		//
#if PY_MAJOR_VERSION >= 3
		if(!PyLong_Check(tempItem))
#else
		if(!PyInt_Check(tempItem))
#endif
		{
			pabort("non-integer contained in tuple\n");
		}
#if PY_MAJOR_VERSION >= 3
		tx[i] = (uint8_t)PyLong_AsSsize_t(tempItem);
#else
		tx[i] = (uint8_t)PyInt_AsSsize_t(tempItem);
#endif

		i++;

	}

	struct spi_ioc_transfer tr = {
		.tx_buf = (unsigned long)tx,
		.rx_buf = (unsigned long)rx,
		.len = tupleSize,
		.delay_usecs = delay,
		.speed_hz = speed,
		.bits_per_word = bits,
                .cs_change = 0,
	};

	ret = ioctl(fd, SPI_IOC_MESSAGE(1), &tr);
	if (ret < 1)
		pabort("can't send spi message");

	transferTuple = PyTuple_New(tupleSize);
	for(i=0;i<tupleSize;i++)
		PyTuple_SetItem(transferTuple, i, Py_BuildValue("i",rx[i]));

	return transferTuple;
}


static PyObject* closeSPI(PyObject* self,PyObject* args)
{
	close(fd);
	Py_RETURN_NONE;
}

static PyMethodDef SpiMethods[] =
{
	{"openSPI", (PyCFunction)openSPI, METH_VARARGS | METH_KEYWORDS, "Open SPI Port."},
	{"transfer", (PyCFunction)transfer, METH_VARARGS, "Transfer data."},
	{"closeSPI", (PyCFunction)closeSPI, METH_NOARGS, "Close SPI port."},
	{NULL, NULL, 0, NULL}
};

#if PY_MAJOR_VERSION >= 3
    static struct PyModuleDef moduledef = {
        PyModuleDef_HEAD_INIT,
        "spi",     /* m_name */
        "spi library",  /* m_doc */
        -1,                  /* m_size */
        SpiMethods,    /* m_methods */
        NULL,                /* m_reload */
        NULL,                /* m_traverse */
        NULL,                /* m_clear */
        NULL,                /* m_free */
    };
#endif

PyMODINIT_FUNC

#if PY_MAJOR_VERSION >= 3
PyInit_spi(void)
#else
initspi(void)
#endif
{
#if PY_MAJOR_VERSION >= 3
        PyObject *module = PyModule_Create(&moduledef);
#else
	(void) Py_InitModule("spi", SpiMethods);
#endif

#if PY_MAJOR_VERSION >= 3
    return module;
#endif
}