wiringPiSPI.c
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/*
* wiringPiSPI.c:
* Simplified SPI access routines
* Copyright (c) 2012-2015 Gordon Henderson
***********************************************************************
* This file is part of wiringPi:
* https://projects.drogon.net/raspberry-pi/wiringpi/
*
* wiringPi is free software: you can redistribute it and/or modify
* it under the terms of the GNU Lesser General Public License as
* published by the Free Software Foundation, either version 3 of the
* License, or (at your option) any later version.
*
* wiringPi 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 Lesser General Public License for more details.
*
* You should have received a copy of the GNU Lesser General Public
* License along with wiringPi.
* If not, see <http://www.gnu.org/licenses/>.
***********************************************************************
*/
#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 "wiringPiSPI.h"
// The SPI bus parameters
// Variables as they need to be passed as pointers later on
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] ;
/*
* wiringPiSPIGetFd:
* Return the file-descriptor for the given channel
*********************************************************************************
*/
int wiringPiSPIGetFd (int channel)
{
return spiFds [channel & 1] ;
}
/*
* wiringPiSPIDataRW:
* Write and Read a block of data over the SPI bus.
* Note the data ia being read into the transmit buffer, so will
* overwrite it!
* This is also a full-duplex operation.
*********************************************************************************
*/
int wiringPiSPIDataRW (int channel, unsigned char *data, int len)
{
struct spi_ioc_transfer spi ;
channel &= 1 ;
// Mentioned in spidev.h but not used in the original kernel documentation
// test program )-:
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) ;
}
/*
* wiringPiSPISetupMode:
* Open the SPI device, and set it up, with the mode, etc.
*********************************************************************************
*/
int wiringPiSPISetupMode (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 ;
}
/*
* wiringPiSPISetup:
* Open the SPI device, and set it up, etc. in the default MODE 0
*********************************************************************************
*/
int wiringPiSPISetup (int channel, int speed)
{
return wiringPiSPISetupMode (channel, speed, 0) ;
}