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wiringPi/wiringPi/wiringPiFace.c

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/*
* wiringPiFace:
* Arduino compatable (ish) Wiring library for the Raspberry Pi
* Copyright (c) 2012 Gordon Henderson
*
* This file to interface with the PiFace peripheral device which
* has an MCP23S17 GPIO device connected via the SPI bus.
*
***********************************************************************
* 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 <stdio.h>
#include <stdint.h>
#include <fcntl.h>
#include <sys/ioctl.h>
#include <sys/types.h>
#include <linux/spi/spidev.h>
#include "wiringPi.h"
// The SPI bus parameters
// Variables as they need to be passed as pointers later on
static char *spiDevice = "/dev/spidev0.0" ;
static uint8_t spiMode = 0 ;
static uint8_t spiBPW = 8 ;
static uint32_t spiSpeed = 5000000 ;
static uint16_t spiDelay = 0;
// Locals here to keep track of everything
static int spiFd ;
// The MCP23S17 doesn't have bit-set operations, so it's
// cheaper to keep a copy here than to read/modify/write it
uint8_t dataOutRegister = 0 ;
uint8_t pudRegister = 0 ;
// MCP23S17 Registers
#define IOCON 0x0A
#define IODIRA 0x00
#define IPOLA 0x02
#define GPINTENA 0x04
#define DEFVALA 0x06
#define INTCONA 0x08
#define GPPUA 0x0C
#define INTFA 0x0E
#define INTCAPA 0x10
#define GPIOA 0x12
#define OLATA 0x14
#define IODIRB 0x01
#define IPOLB 0x03
#define GPINTENB 0x05
#define DEFVALB 0x07
#define INTCONB 0x09
#define GPPUB 0x0D
#define INTFB 0x0F
#define INTCAPB 0x11
#define GPIOB 0x13
#define OLATB 0x15
// Bits in the IOCON register
#define IOCON_BANK_MODE 0x80
#define IOCON_MIRROR 0x40
#define IOCON_SEQOP 0x20
#define IOCON_DISSLW 0x10
#define IOCON_HAEN 0x08
#define IOCON_ODR 0x04
#define IOCON_INTPOL 0x02
#define IOCON_UNUSED 0x01
// Default initialisation mode
#define IOCON_INIT (IOCON_SEQOP)
// Command codes
#define CMD_WRITE 0x40
#define CMD_READ 0x41
/*
* writeByte:
* Write a byte to a register on the MCP23S17 on the SPI bus.
* This is using the synchronous access mechanism.
*********************************************************************************
*/
static void writeByte (uint8_t reg, uint8_t data)
{
uint8_t spiBufTx [3] ;
uint8_t spiBufRx [3] ;
struct spi_ioc_transfer spi ;
spiBufTx [0] = CMD_WRITE ;
spiBufTx [1] = reg ;
spiBufTx [2] = data ;
spi.tx_buf = (unsigned long)spiBufTx ;
spi.rx_buf = (unsigned long)spiBufRx ;
spi.len = 3 ;
spi.delay_usecs = spiDelay ;
spi.speed_hz = spiSpeed ;
spi.bits_per_word = spiBPW ;
ioctl (spiFd, SPI_IOC_MESSAGE(1), &spi) ;
}
/*
* readByte:
* Read a byte from a register on the MCP23S17 on the SPI bus.
* This is the synchronous access mechanism.
* What appears to happen is that the data returned is at
* the same offset as the number of bytes written to the device. So if we
* write 2 bytes (e.g. command then register number), then the data returned
* will by at the 3rd byte...
*********************************************************************************
*/
static uint8_t readByte (uint8_t reg)
{
uint8_t tx [4] ;
uint8_t rx [4] ;
struct spi_ioc_transfer spi ;
tx [0] = CMD_READ ;
tx [1] = reg ;
tx [2] = 0 ;
spi.tx_buf = (unsigned long)tx ;
spi.rx_buf = (unsigned long)rx ;
spi.len = 3 ;
spi.delay_usecs = spiDelay ;
spi.speed_hz = spiSpeed ;
spi.bits_per_word = spiBPW ;
ioctl (spiFd, SPI_IOC_MESSAGE(1), &spi) ;
return rx [2] ;
}
/*
* digitalWritePiFace:
* Perform the digitalWrite function on the PiFace board
*********************************************************************************
*/
void digitalWritePiFace (int pin, int value)
{
uint8_t mask = 1 << pin ;
if (value == 0)
dataOutRegister &= (~mask) ;
else
dataOutRegister |= mask ;
writeByte (GPIOA, dataOutRegister) ;
}
void digitalWritePiFaceSpecial (int pin, int value)
{
uint8_t mask = 1 << pin ;
uint8_t old ;
old = readByte (GPIOA) ;
if (value == 0)
old &= (~mask) ;
else
old |= mask ;
writeByte (GPIOA, old) ;
}
/*
* digitalReadPiFace:
* Perform the digitalRead function on the PiFace board
*********************************************************************************
*/
int digitalReadPiFace (int pin)
{
uint8_t mask = 1 << pin ;
if ((readByte (GPIOB) & mask) != 0)
return HIGH ;
else
return LOW ;
}
/*
* pullUpDnControlPiFace:
* Perform the pullUpDnControl function on the PiFace board
*********************************************************************************
*/
void pullUpDnControlPiFace (int pin, int pud)
{
uint8_t mask = 1 << pin ;
if (pud == PUD_UP)
pudRegister |= mask ;
else
pudRegister &= (~mask) ;
writeByte (GPPUB, pudRegister) ;
}
void pullUpDnControlPiFaceSpecial (int pin, int pud)
{
uint8_t mask = 1 << pin ;
uint8_t old ;
old = readByte (GPPUB) ;
if (pud == PUD_UP)
old |= mask ;
else
old &= (~mask) ;
writeByte (GPPUB, old) ;
}
/*
* Dummy functions that are not used in this mode
*********************************************************************************
*/
void pinModePiFace (int pin, int mode) {}
void pwmWritePiFace (int pin, int value) {}
int waitForInterruptPiFace (int pin, int mS) { return 0 ; }
/*
* wiringPiSetupPiFace
* Setup the SPI interface and initialise the MCP23S17 chip
*********************************************************************************
*/
static int _wiringPiSetupPiFace (void)
{
if ((spiFd = open (spiDevice, O_RDWR)) < 0)
return -1 ;
// Set SPI parameters
// Why are we doing a read after write?
// I don't know - just blindliy copying an example elsewhere... -GH-
if (ioctl (spiFd, SPI_IOC_WR_MODE, &spiMode) < 0)
return -1 ;
if (ioctl (spiFd, SPI_IOC_RD_MODE, &spiMode) < 0)
return -1 ;
if (ioctl (spiFd, SPI_IOC_WR_BITS_PER_WORD, &spiBPW) < 0)
return -1 ;
if (ioctl (spiFd, SPI_IOC_RD_BITS_PER_WORD, &spiBPW) < 0)
return -1 ;
if (ioctl (spiFd, SPI_IOC_WR_MAX_SPEED_HZ, &spiSpeed) < 0)
return -1 ;
if (ioctl (spiFd, SPI_IOC_RD_MAX_SPEED_HZ, &spiSpeed) < 0)
return -1 ;
// Setup the MCP23S17
writeByte (IOCON, IOCON_INIT) ;
writeByte (IODIRA, 0x00) ; // Port A -> Outputs
writeByte (IODIRB, 0xFF) ; // Port B -> Inputs
return 0 ;
}
int wiringPiSetupPiFace (void)
{
int x = _wiringPiSetupPiFace () ;
if (x != 0)
return x ;
writeByte (GPIOA, 0x00) ; // Set all outptus off
writeByte (GPPUB, 0x00) ; // Disable any pull-ups on port B
pinMode = pinModePiFace ;
pullUpDnControl = pullUpDnControlPiFace ;
digitalWrite = digitalWritePiFace ;
pwmWrite = pwmWritePiFace ;
digitalRead = digitalReadPiFace ;
waitForInterrupt = waitForInterruptPiFace ;
return 0 ;
}
/*
* wiringPiSetupPiFaceForGpioProg:
* Setup the SPI interface and initialise the MCP23S17 chip
* Special version for the gpio program
*********************************************************************************
*/
int wiringPiSetupPiFaceForGpioProg (void)
{
int x = _wiringPiSetupPiFace () ;
if (x != 0)
return x ;
pinMode = pinModePiFace ;
pullUpDnControl = pullUpDnControlPiFaceSpecial ;
digitalWrite = digitalWritePiFaceSpecial ;
pwmWrite = pwmWritePiFace ;
digitalRead = digitalReadPiFace ;
waitForInterrupt = waitForInterruptPiFace ;
return 0 ;
}
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