SPISetup.cpp

#include <stdint.h>
#include <fcntl.h>
#include <errno.h>
#include <string.h>
#include <sys/ioctl.h>
#include <asm/ioctl.h>
#include <linux/spi/spidev.h>

#include "wiringPi.h"
#include "SPISetup.h"


static const char       *spiDev0  = "/dev/spidev0.0" ;
static const char       *spiDev1  = "/dev/spidev0.1" ;
static const uint8_t     spiBPW   = 8 ;
static const uint16_t    spiDelay = 0 ;

static uint32_t    spiSpeeds [2] ;
static int         spiFds [2] ;

int SPIGetFd (int channel)
{
  return spiFds [channel & 1] ;
}

/********************************************************************
 * This function writes data "data" of length "length" to the spidev
 * device. Data shifted in from the spidev device is saved back into
 * "data".
 * ******************************************************************/
int SPIDataRW( int channel, unsigned char *data, int len ){

  struct spi_ioc_transfer spi ;
  
  channel &= 1 ;
  
  memset (&spi, 0, sizeof (spi)) ;

  spi.tx_buf        = (unsigned long)data ;
  spi.rx_buf        = (unsigned long)data ;
  spi.len           = len ;
  spi.delay_usecs   = spiDelay ;
  spi.speed_hz      = spiSpeeds [channel] ;
  spi.bits_per_word = spiBPW ;

  return ioctl (spiFds [channel], SPI_IOC_MESSAGE(1), &spi) ;
}

int SPISetupMode (int channel, int speed, int mode)
{
  int fd ;

  mode    &= 3 ;	// Mode is 0, 1, 2 or 3
  channel &= 1 ;	// Channel is 0 or 1

  if ((fd = open (channel == 0 ? spiDev0 : spiDev1, O_RDWR)) < 0)
    return wiringPiFailure (WPI_ALMOST, "Unable to open SPI device: %s\n", strerror (errno)) ;

  spiSpeeds [channel] = speed ;
  spiFds    [channel] = fd ;

// Set SPI parameters.

  if (ioctl (fd, SPI_IOC_WR_MODE, &mode)            < 0)
    return wiringPiFailure (WPI_ALMOST, "SPI Mode Change failure: %s\n", strerror (errno)) ;
  
  if (ioctl (fd, SPI_IOC_WR_BITS_PER_WORD, &spiBPW) < 0)
    return wiringPiFailure (WPI_ALMOST, "SPI BPW Change failure: %s\n", strerror (errno)) ;

  if (ioctl (fd, SPI_IOC_WR_MAX_SPEED_HZ, &speed)   < 0)
    return wiringPiFailure (WPI_ALMOST, "SPI Speed Change failure: %s\n", strerror (errno)) ;

  return fd ;
}


/*
 * SPISetup:
 *	Open the SPI device, and set it up, etc. in the default MODE 0
 *********************************************************************************
 */

int SPISetup (int channel, int speed)
{
  return SPISetupMode (channel, speed, 0) ;
}