adcPythonC.c

#include <Python.h>
#include "mraa_raspberry_pi_pinmap.h"


mraa_gpio_context MCP3208_DIN;
mraa_gpio_context MCP3208_DOUT;
mraa_gpio_context MCP3208_CLK;
mraa_gpio_context MCP3208_CS;
/*
* to compile and create a share object run the following command
* gcc -shared -I /usr/include/python2.7/ -l python2.7 -l mraa -o adcPythonC.so adcPythonC.c
* Function to be called from Python
*/
static PyObject* py_testFunction(PyObject* self, PyObject* args)
{
	  char *s = "Hello from C!";
	  return Py_BuildValue("s", s);
}

/*
 * Read ADC Function set up for a MCP3208 using bit bang mode. 
 */
static PyObject* py_adcRead(PyObject* self, PyObject* args)
{
	int channel, i,val;
	PyArg_ParseTuple(args, "i", &channel);
	mraa_gpio_write (MCP3208_DIN, 0);
	mraa_gpio_write (MCP3208_CLK, 0);
	mraa_gpio_write (MCP3208_CS, 0);

	channel = channel | 0x18;
	for (i = 0; i < 5; i ++)
	{
		if (channel & 0x10)
		{
			mraa_gpio_write (MCP3208_DIN, 1);
		}
		else
		{
			mraa_gpio_write (MCP3208_DIN, 0);
		}
		channel <<= 1;

		mraa_gpio_write (MCP3208_CLK, 0);
		mraa_gpio_write (MCP3208_CLK, 1);
	}

	mraa_gpio_write (MCP3208_CLK, 0);
	mraa_gpio_write (MCP3208_CLK, 1);

	mraa_gpio_write (MCP3208_CLK, 0);
	mraa_gpio_write (MCP3208_CLK, 1);

	val = 0;
	for (i = 0; i < 12; i ++)
	{
		mraa_gpio_write (MCP3208_CLK, 0);
		mraa_gpio_write (MCP3208_CLK, 1);
		
		val = (val << 1) | ((int) mraa_gpio_read (MCP3208_DOUT));	
	}
	
	mraa_gpio_write (MCP3208_CS, 1);
	mraa_gpio_write (MCP3208_DIN, 0);
	mraa_gpio_write (MCP3208_CLK, 0);
	return Py_BuildValue("i", val);
}

/*
 * Bind Python function names to the C functions
 */
static PyMethodDef adcPythonC_methods[] = {
	  {"testFunction", py_testFunction, METH_VARARGS},
	  {"adcRead", py_adcRead, METH_VARARGS},
	  {NULL, NULL}
};

/*
 * This is called on initialization of the module.  
 * Put set up information here
 *
void initadcPythonC()
{
	(void) Py_InitModule("adcPythonC", adcPythonC_methods);
	MCP3208_DIN = mraa_gpio_init (SPI_MOSI_PIN);
	MCP3208_DOUT = mraa_gpio_init (SPI_MISO_PIN);
	MCP3208_CLK = mraa_gpio_init (SPI_CLK_PIN);
	MCP3208_CS = mraa_gpio_init (SPI_CS0_PIN);
        sleep(1); // Need a delay before setting the direction.	
	mraa_gpio_dir(MCP3208_DIN, MRAA_GPIO_OUT_HIGH);
	mraa_gpio_dir(MCP3208_DOUT, MRAA_GPIO_IN);
	mraa_gpio_dir(MCP3208_CLK, MRAA_GPIO_OUT);
	mraa_gpio_dir(MCP3208_CS, MRAA_GPIO_OUT); */
static struct PyModuleDef adcPythonC =
{
    PyModuleDef_HEAD_INIT,
    "adcPythonC", /* name of module */
    "",          /* module documentation, may be NULL */
    -1,          /* size of per-interpreter state of the module, or -1 if the module keeps state in global variables. */
    adcPythonC_methods
};


/*
 * This is called on initialization of the module.  
 * Put set up information here -  utilizing Python 3
 */
PyMODINIT_FUNC PyInit_adcPythonC(void)
{
        return PyModule_Create(&adcPythonC);                             

}