WiringPi/wiringPi/wiringPi.c

/*
 * wiringPi:
 *	Arduino compatable (ish) Wiring library for the Raspberry Pi
 *	Copyright (c) 2012 Gordon Henderson
 *	Additional code for pwmSetClock by Chris Hall <chris@kchall.plus.com>
 *
 *	Thanks to code samples from Gert Jan van Loo and the
 *	BCM2835 ARM Peripherals manual, however it's missing
 *	the clock section /grr/mutter/
 ***********************************************************************
 * 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/>.
 ***********************************************************************
 */

// Revisions:
//	19 Jul 2012:
//		Moved to the LGPL
//		Added an abstraction layer to the main routines to save a tiny
//		bit of run-time and make the clode a little cleaner (if a little
//		larger)
//		Added waitForInterrupt code
//		Added piHiPri code
//
//	 9 Jul 2012:
//		Added in support to use the /sys/class/gpio interface.
//	 2 Jul 2012:
//		Fixed a few more bugs to do with range-checking when in GPIO mode.
//	11 Jun 2012:
//		Fixed some typos.
//		Added c++ support for the .h file
//		Added a new function to allow for using my "pin" numbers, or native
//			GPIO pin numbers.
//		Removed my busy-loop delay and replaced it with a call to delayMicroseconds
//
//	02 May 2012:
//		Added in the 2 UART pins
//		Change maxPins to numPins to more accurately reflect purpose


#include <stdio.h>
#include <stdint.h>
#include <stdlib.h>
#include <ctype.h>
#include <poll.h>
#include <unistd.h>
#include <errno.h>
#include <string.h>
#include <time.h>
#include <fcntl.h>
#include <pthread.h>
#include <sys/time.h>
#include <sys/mman.h>
#include <sys/stat.h>
#include <sys/wait.h>
#include <sys/ioctl.h>

#include "wiringPi.h"

// Function stubs

void (*pinMode)           (int pin, int mode) ;
int  (*getAlt)            (int pin) ;
void (*pullUpDnControl)   (int pin, int pud) ;
void (*digitalWrite)      (int pin, int value) ;
void (*digitalWriteByte)  (int value) ;
void (*pwmWrite)          (int pin, int value) ;
void (*gpioClockSet)      (int pin, int value) ;
void (*setPadDrive)       (int group, int value) ;
int  (*digitalRead)       (int pin) ;
int  (*waitForInterrupt)  (int pin, int mS) ;
void (*pwmSetMode)        (int mode) ;
void (*pwmSetRange)       (unsigned int range) ;
void (*pwmSetClock)       (int divisor) ;


#ifndef	TRUE
#define	TRUE	(1==1)
#define	FALSE	(1==2)
#endif

// BCM Magic

#define	BCM_PASSWORD		0x5A000000


// The BCM2835 has 54 GPIO pins.
//	BCM2835 data sheet, Page 90 onwards.
//	There are 6 control registers, each control the functions of a block
//	of 10 pins.
//	Each control register has 10 sets of 3 bits per GPIO pin - the ALT values
//
//	000 = GPIO Pin X is an input
//	001 = GPIO Pin X is an output
//	100 = GPIO Pin X takes alternate function 0
//	101 = GPIO Pin X takes alternate function 1
//	110 = GPIO Pin X takes alternate function 2
//	111 = GPIO Pin X takes alternate function 3
//	011 = GPIO Pin X takes alternate function 4
//	010 = GPIO Pin X takes alternate function 5
//
// So the 3 bits for port X are:
//	X / 10 + ((X % 10) * 3)

// Port function select bits

#define	FSEL_INPT		0b000
#define	FSEL_OUTP		0b001
#define	FSEL_ALT0		0b100
#define	FSEL_ALT0		0b100
#define	FSEL_ALT1		0b101
#define	FSEL_ALT2		0b110
#define	FSEL_ALT3		0b111
#define	FSEL_ALT4		0b011
#define	FSEL_ALT5		0b010

// Access from ARM Running Linux
//	Taken from Gert/Doms code. Some of this is not in the manual
//	that I can find )-:

#define BCM2708_PERI_BASE	                     0x20000000
#define GPIO_PADS		(BCM2708_PERI_BASE + 0x00100000)
#define CLOCK_BASE		(BCM2708_PERI_BASE + 0x00101000)
#define GPIO_BASE		(BCM2708_PERI_BASE + 0x00200000)
#define GPIO_TIMER		(BCM2708_PERI_BASE + 0x0000B000)
#define GPIO_PWM		(BCM2708_PERI_BASE + 0x0020C000)

#define	PAGE_SIZE		(4*1024)
#define	BLOCK_SIZE		(4*1024)

// PWM
//	Word offsets into the PWM control region

#define	PWM_CONTROL 0
#define	PWM_STATUS  1
#define	PWM0_RANGE  4
#define	PWM0_DATA   5
#define	PWM1_RANGE  8
#define	PWM1_DATA   9

//	Clock regsiter offsets

#define	PWMCLK_CNTL	40
#define	PWMCLK_DIV	41

#define	PWM0_MS_MODE    0x0080  // Run in MS mode
#define	PWM0_USEFIFO    0x0020  // Data from FIFO
#define	PWM0_REVPOLAR   0x0010  // Reverse polarity
#define	PWM0_OFFSTATE   0x0008  // Ouput Off state
#define	PWM0_REPEATFF   0x0004  // Repeat last value if FIFO empty
#define	PWM0_SERIAL     0x0002  // Run in serial mode
#define	PWM0_ENABLE     0x0001  // Channel Enable

#define	PWM1_MS_MODE    0x8000  // Run in MS mode
#define	PWM1_USEFIFO    0x2000  // Data from FIFO
#define	PWM1_REVPOLAR   0x1000  // Reverse polarity
#define	PWM1_OFFSTATE   0x0800  // Ouput Off state
#define	PWM1_REPEATFF   0x0400  // Repeat last value if FIFO empty
#define	PWM1_SERIAL     0x0200  // Run in serial mode
#define	PWM1_ENABLE     0x0100  // Channel Enable

// Timer
//	Word offsets

#define	TIMER_LOAD	(0x400 >> 2)
#define	TIMER_VALUE	(0x404 >> 2)
#define	TIMER_CONTROL	(0x408 >> 2)
#define	TIMER_IRQ_CLR	(0x40C >> 2)
#define	TIMER_IRQ_RAW	(0x410 >> 2)
#define	TIMER_IRQ_MASK	(0x414 >> 2)
#define	TIMER_RELOAD	(0x418 >> 2)
#define	TIMER_PRE_DIV	(0x41C >> 2)
#define	TIMER_COUNTER	(0x420 >> 2)

// Locals to hold pointers to the hardware

static volatile uint32_t *gpio ;
static volatile uint32_t *pwm ;
static volatile uint32_t *clk ;
static volatile uint32_t *pads ;
static volatile uint32_t *timer ;
static volatile uint32_t *timerIrqRaw ;

// Time for easy calculations

static uint64_t epochMilli, epochMicro ;

// Misc

static int wiringPiMode = WPI_MODE_UNINITIALISED ;

// Debugging

int wiringPiDebug = FALSE ;

// sysFds:
//	Map a file descriptor from the /sys/class/gpio/gpioX/value

static int sysFds [64] ;

// ISR Data

static void (*isrFunctions [64])(void) ;


// Doing it the Arduino way with lookup tables...
//	Yes, it's probably more innefficient than all the bit-twidling, but it
//	does tend to make it all a bit clearer. At least to me!

// pinToGpio:
//	Take a Wiring pin (0 through X) and re-map it to the BCM_GPIO pin
//	Cope for 2 different board revieions here

static int *pinToGpio ;

static int pinToGpioR1 [64] =
{
  17, 18, 21, 22, 23, 24, 25, 4,	// From the Original Wiki - GPIO 0 through 7
   0,  1,				// I2C  - SDA0, SCL0
   8,  7,				// SPI  - CE1, CE0
  10,  9, 11, 				// SPI  - MOSI, MISO, SCLK
  14, 15,				// UART - Tx, Rx

// Padding:

      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,	// ... 31
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,	// ... 47
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,	// ... 63
} ;

static int pinToGpioR2 [64] =
{
  17, 18, 27, 22, 23, 24, 25, 4,	// From the Original Wiki - GPIO 0 through 7:	wpi  0 -  7
   2,  3,				// I2C  - SDA0, SCL0				wpi  8 -  9
   8,  7,				// SPI  - CE1, CE0				wpi 10 - 11
  10,  9, 11, 				// SPI  - MOSI, MISO, SCLK			wpi 12 - 14
  14, 15,				// UART - Tx, Rx				wpi 15 - 16
  28, 29, 30, 31,			// New GPIOs 8 though 11			wpi 17 - 20

// Padding:

                      -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,	// ... 31
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,	// ... 47
  -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1, -1,	// ... 63
} ;


// gpioToGPFSEL:
//	Map a BCM_GPIO pin to it's control port. (GPFSEL 0-5)

static uint8_t gpioToGPFSEL [] =
{
  0,0,0,0,0,0,0,0,0,0,
  1,1,1,1,1,1,1,1,1,1,
  2,2,2,2,2,2,2,2,2,2,
  3,3,3,3,3,3,3,3,3,3,
  4,4,4,4,4,4,4,4,4,4,
  5,5,5,5,5,5,5,5,5,5,
} ;


// gpioToShift
//	Define the shift up for the 3 bits per pin in each GPFSEL port

static uint8_t gpioToShift [] =
{
  0,3,6,9,12,15,18,21,24,27,
  0,3,6,9,12,15,18,21,24,27,
  0,3,6,9,12,15,18,21,24,27,
  0,3,6,9,12,15,18,21,24,27,
  0,3,6,9,12,15,18,21,24,27,
} ;


// gpioToGPSET:
//	(Word) offset to the GPIO Set registers for each GPIO pin

static uint8_t gpioToGPSET [] =
{
   7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7, 7,
   8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8, 8,
} ;


// gpioToGPCLR:
//	(Word) offset to the GPIO Clear registers for each GPIO pin

static uint8_t gpioToGPCLR [] =
{
  10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,10,
  11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,11,
} ;


// gpioToGPLEV:
//	(Word) offset to the GPIO Input level registers for each GPIO pin

static uint8_t gpioToGPLEV [] =
{
  13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,13,
  14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,14,
} ;


#ifdef notYetReady
// gpioToEDS
//	(Word) offset to the Event Detect Status

static uint8_t gpioToEDS [] =
{
  16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,16,
  17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,17,
} ;

// gpioToREN
//	(Word) offset to the Rising edgde ENable register

static uint8_t gpioToREN [] =
{
  19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,19,
  20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,20,
} ;

// gpioToFEN
//	(Word) offset to the Falling edgde ENable register

static uint8_t gpioToFEN [] =
{
  22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,22,
  23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,23,
} ;
#endif


// GPPUD:
//	GPIO Pin pull up/down register

#define	GPPUD	37

// gpioToPUDCLK
//	(Word) offset to the Pull Up Down Clock regsiter

static uint8_t gpioToPUDCLK [] =
{
  38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,38,
  39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,39,
} ;


// gpioToPwmALT
//	the ALT value to put a GPIO pin into PWM mode

static uint8_t gpioToPwmALT [] =
{
          0,         0,         0,         0,         0,         0,         0,         0,	//  0 ->  7
          0,         0,         0,         0, FSEL_ALT0, FSEL_ALT0,         0,         0, 	//  8 -> 15
          0,         0, FSEL_ALT5, FSEL_ALT5,         0,         0,         0,         0, 	// 16 -> 23
          0,         0,         0,         0,         0,         0,         0,         0,	// 24 -> 31
          0,         0,         0,         0,         0,         0,         0,         0,	// 32 -> 39
  FSEL_ALT0, FSEL_ALT0,         0,         0,         0, FSEL_ALT0,         0,         0,	// 40 -> 47
          0,         0,         0,         0,         0,         0,         0,         0,	// 48 -> 55
          0,         0,         0,         0,         0,         0,         0,         0,	// 56 -> 63
} ;

// gpioToPwmPort
//	The port value to put a GPIO pin into PWM mode

static uint8_t gpioToPwmPort [] =
{
          0,         0,         0,         0,         0,         0,         0,         0,	//  0 ->  7
          0,         0,         0,         0, PWM0_DATA, PWM1_DATA,         0,         0, 	//  8 -> 15
          0,         0, PWM0_DATA, PWM1_DATA,         0,         0,         0,         0, 	// 16 -> 23
          0,         0,         0,         0,         0,         0,         0,         0,	// 24 -> 31
          0,         0,         0,         0,         0,         0,         0,         0,	// 32 -> 39
  PWM0_DATA, PWM1_DATA,         0,         0,         0, PWM1_DATA,         0,         0,	// 40 -> 47
          0,         0,         0,         0,         0,         0,         0,         0,	// 48 -> 55
          0,         0,         0,         0,         0,         0,         0,         0,	// 56 -> 63

} ;

// gpioToGpClkALT:
//	ALT value to put a GPIO pin into GP Clock mode.
//	On the Pi we can really only use BCM_GPIO_4 and BCM_GPIO_21
//	for clocks 0 and 1 respectivey, however I'll include the full
//	list for completeness - maybe one day...

#define	GPIO_CLOCK_SOURCE	1

// gpioToGpClkALT0:

static uint8_t gpioToGpClkALT0 [] =
{
          0,         0,         0,         0, FSEL_ALT0, FSEL_ALT0, FSEL_ALT0,         0,	//  0 ->  7
          0,         0,         0,         0,         0,         0,         0,         0, 	//  8 -> 15
          0,         0,         0,         0, FSEL_ALT5, FSEL_ALT5,         0,         0, 	// 16 -> 23
          0,         0,         0,         0,         0,         0,         0,         0,	// 24 -> 31
  FSEL_ALT0,         0, FSEL_ALT0,         0,         0,         0,         0,         0,	// 32 -> 39
          0,         0, FSEL_ALT0, FSEL_ALT0, FSEL_ALT0,         0,         0,         0,	// 40 -> 47
          0,         0,         0,         0,         0,         0,         0,         0,	// 48 -> 55
          0,         0,         0,         0,         0,         0,         0,         0,	// 56 -> 63
} ;

// gpioToClk:
//	(word) Offsets to the clock Control and Divisor register

static uint8_t gpioToClkCon [] =
{
         -1,        -1,        -1,        -1,        28,        30,        32,        -1,	//  0 ->  7
         -1,        -1,        -1,        -1,        -1,        -1,        -1,        -1, 	//  8 -> 15
         -1,        -1,        -1,        -1,        28,        30,        -1,        -1, 	// 16 -> 23
         -1,        -1,        -1,        -1,        -1,        -1,        -1,        -1,	// 24 -> 31
         28,        -1,        28,        -1,        -1,        -1,        -1,        -1,	// 32 -> 39
         -1,        -1,        28,        30,        28,        -1,        -1,        -1,	// 40 -> 47
         -1,        -1,        -1,        -1,        -1,        -1,        -1,        -1,	// 48 -> 55
         -1,        -1,        -1,        -1,        -1,        -1,        -1,        -1,	// 56 -> 63
} ;

static uint8_t gpioToClkDiv [] =
{
         -1,        -1,        -1,        -1,        29,        31,        33,        -1,	//  0 ->  7
         -1,        -1,        -1,        -1,        -1,        -1,        -1,        -1, 	//  8 -> 15
         -1,        -1,        -1,        -1,        29,        31,        -1,        -1, 	// 16 -> 23
         -1,        -1,        -1,        -1,        -1,        -1,        -1,        -1,	// 24 -> 31
         29,        -1,        29,        -1,        -1,        -1,        -1,        -1,	// 32 -> 39
         -1,        -1,        29,        31,        29,        -1,        -1,        -1,	// 40 -> 47
         -1,        -1,        -1,        -1,        -1,        -1,        -1,        -1,	// 48 -> 55
         -1,        -1,        -1,        -1,        -1,        -1,        -1,        -1,	// 56 -> 63
} ;


/*
 * Functions
 *********************************************************************************
 */


/*
 * wpiPinToGpio:
 *	Translate a wiringPi Pin number to native GPIO pin number.
 *	(We don't use this here, prefering to just do the lookup directly,
 *	but it's been requested!)
 *********************************************************************************
 */

int wpiPinToGpio (int wpiPin)
{
  return pinToGpio [wpiPin & 63] ;
}


/*
 * piBoardRev:
 *	Return a number representing the hardware revision of the board.
 *	Revision is currently 1 or 2. -1 is returned on error.
 *
 *	Much confusion here )-:
 *	Seems there are some boards with 0000 in them (mistake in manufacture)
 *	and some board with 0005 in them (another mistake in manufacture?)
 *	So the distinction between boards that I can see is:
 *	0000 - Error
 *	0001 - Not used
 *	0002 - Rev 1
 *	0003 - Rev 1
 *	0004 - Rev 2 (Early reports?
 *	0005 - Rev 2 (but error?)
 *	0006 - Rev 2
 *	0008 - Rev 2 - Model A
 *	000e - Rev 2 + 512MB
 *	000f - Rev 2 + 512MB
 *
 *	A small thorn is the olde style overvolting - that will add in
 *		1000000
 *
 *********************************************************************************
 */

static void piBoardRevOops (char *why)
{
  fprintf (stderr, "piBoardRev: Unable to determine board revision from /proc/cpuinfo\n") ;
  fprintf (stderr, " -> %s\n", why) ;
  fprintf (stderr, " ->  You may want to check:\n") ;
  fprintf (stderr, " ->  http://www.raspberrypi.org/phpBB3/viewtopic.php?p=184410#p184410\n") ;
  exit (EXIT_FAILURE) ;
}

int piBoardRev (void)
{
  FILE *cpuFd ;
  char line [120] ;
  char *c, lastChar ;
  static int  boardRev = -1 ;

  if (boardRev != -1)	// No point checking twice
    return boardRev ;

  if ((cpuFd = fopen ("/proc/cpuinfo", "r")) == NULL)
    piBoardRevOops ("Unable to open /proc/cpuinfo") ;

  while (fgets (line, 120, cpuFd) != NULL)
    if (strncmp (line, "Revision", 8) == 0)
      break ;

  fclose (cpuFd) ;

  if (strncmp (line, "Revision", 8) != 0)
    piBoardRevOops ("No \"Revision\" line") ;

  for (c = &line [strlen (line) - 1] ; (*c == '\n') || (*c == '\r') ; --c)
    *c = 0 ;
  
  if (wiringPiDebug)
    printf ("piboardRev: Revision string: %s\n", line) ;

  for (c = line ; *c ; ++c)
    if (isdigit (*c))
      break ;

  if (!isdigit (*c))
    piBoardRevOops ("No numeric revision string") ;

// If you have overvolted the Pi, then it appears that the revision
//	has 100000 added to it!

  if (wiringPiDebug)
    if (strlen (c) != 4)
      printf ("piboardRev: This Pi has/is overvolted!\n") ;

  lastChar = line [strlen (line) - 1] ;

  if (wiringPiDebug)
    printf ("piboardRev: lastChar is: '%c' (%d, 0x%02X)\n", lastChar, lastChar, lastChar) ;

  /**/ if ((lastChar == '2') || (lastChar == '3'))
    boardRev = 1 ;
  else
    boardRev = 2 ;

  if (wiringPiDebug)
    printf ("piBoardRev: Returning revision: %d\n", boardRev) ;

  return boardRev ;
}



/*
 * getAlt:
 *	Returns the ALT bits for a given port. Only really of-use
 *	for the gpio readall command (I think)
 *********************************************************************************
 */

int getAltGpio (int pin)
{
  int fSel, shift, alt ;

  pin &= 63 ;

  fSel    = gpioToGPFSEL [pin] ;
  shift   = gpioToShift  [pin] ;

  alt = (*(gpio + fSel) >> shift) & 7 ;

  return alt ;
}

int getAltWPi (int pin)
{
  return getAltGpio (pinToGpio [pin & 63]) ;
}

int getAltSys (int pin)
{
  return 0 ;
}


/*
 * pwmControl:
 *	Allow the user to control some of the PWM functions
 *********************************************************************************
 */

void pwmSetModeWPi (int mode)
{
  if (mode == PWM_MODE_MS)
    *(pwm + PWM_CONTROL) = PWM0_ENABLE | PWM1_ENABLE | PWM0_MS_MODE | PWM1_MS_MODE ;
  else
    *(pwm + PWM_CONTROL) = PWM0_ENABLE | PWM1_ENABLE ;
}

void pwmSetModeSys (int mode)
{
  return ;
}


void pwmSetRangeWPi (unsigned int range)
{
  *(pwm + PWM0_RANGE) = range ; delayMicroseconds (10) ;
  *(pwm + PWM1_RANGE) = range ; delayMicroseconds (10) ;
}

void pwmSetRangeSys (unsigned int range)
{
  return ;
}

/*
 * pwmSetClockWPi:
 *	Set/Change the PWM clock. Originally my code, but changed
 *	(for the better!) by Chris Hall, <chris@kchall.plus.com>
 *	after further study of the manual and testing with a 'scope
 *********************************************************************************
 */

void pwmSetClockWPi (int divisor)
{
  uint32_t pwm_control ;
  divisor &= 4095 ;

  if (wiringPiDebug)
    printf ("Setting to: %d. Current: 0x%08X\n", divisor, *(clk + PWMCLK_DIV)) ;

  pwm_control = *(pwm + PWM_CONTROL) ;		// preserve PWM_CONTROL

// We need to stop PWM prior to stopping PWM clock in MS mode otherwise BUSY
// stays high.

  *(pwm + PWM_CONTROL) = 0 ;			// Stop PWM

// Stop PWM clock before changing divisor. The delay after this does need to
// this big (95uS occasionally fails, 100uS OK), it's almost as though the BUSY
// flag is not working properly in balanced mode. Without the delay when DIV is
// adjusted the clock sometimes switches to very slow, once slow further DIV
// adjustments do nothing and it's difficult to get out of this mode.

  *(clk + PWMCLK_CNTL) = BCM_PASSWORD | 0x01 ;	// Stop PWM Clock
    delayMicroseconds (110) ;			// prevents clock going sloooow

  while ((*(clk + PWMCLK_CNTL) & 0x80) != 0)	// Wait for clock to be !BUSY
    delayMicroseconds (1) ;

  *(clk + PWMCLK_DIV)  = BCM_PASSWORD | (divisor << 12) ;

  *(clk + PWMCLK_CNTL) = BCM_PASSWORD | 0x11 ;	// Start PWM clock
  *(pwm + PWM_CONTROL) = pwm_control ;		// restore PWM_CONTROL

  if (wiringPiDebug)
    printf ("Set     to: %d. Now    : 0x%08X\n", divisor, *(clk + PWMCLK_DIV)) ;
}

void pwmSetClockSys (int divisor)
{
  return ;
}


#ifdef notYetReady
/*
 * pinED01:
 * pinED10:
 *	Enables edge-detect mode on a pin - from a 0 to a 1 or 1 to 0
 *	Pin must already be in input mode with appropriate pull up/downs set.
 *********************************************************************************
 */

void pinEnableED01Pi (int pin)
{
  pin = pinToGpio [pin & 63] ;
}
#endif



/*
 * digitalWrite:
 *	Set an output bit
 *********************************************************************************
 */

void digitalWriteWPi (int pin, int value)
{
  pin = pinToGpio [pin & 63] ;

  if (value == LOW)
    *(gpio + gpioToGPCLR [pin]) = 1 << (pin & 31) ;
  else
    *(gpio + gpioToGPSET [pin]) = 1 << (pin & 31) ;
}

void digitalWriteGpio (int pin, int value)
{
  pin &= 63 ;

  if (value == LOW)
    *(gpio + gpioToGPCLR [pin]) = 1 << (pin & 31) ;
  else
    *(gpio + gpioToGPSET [pin]) = 1 << (pin & 31) ;
}

void digitalWriteSys (int pin, int value)
{
  pin &= 63 ;

  if (sysFds [pin] != -1)
  {
    if (value == LOW)
      write (sysFds [pin], "0\n", 2) ;
    else
      write (sysFds [pin], "1\n", 2) ;
  }
}


/*
 * digitalWriteByte:
 *	Write an 8-bit byte to the first 8 GPIO pins - try to do it as
 *	fast as possible.
 *	However it still needs 2 operations to set the bits, so any external
 *	hardware must not rely on seeing a change as there will be a change 
 *	to set the outputs bits to zero, then another change to set the 1's
 *********************************************************************************
 */

void digitalWriteByteGpio (int value)
{
  uint32_t pinSet = 0 ;
  uint32_t pinClr = 0 ;
  int mask = 1 ;
  int pin ;

  for (pin = 0 ; pin < 8 ; ++pin)
  {
    if ((value & mask) == 0)
      pinClr |= (1 << pinToGpio [pin]) ;
    else
      pinSet |= (1 << pinToGpio [pin]) ;

    mask <<= 1 ;
  }

  *(gpio + gpioToGPCLR [0]) = pinClr ;
  *(gpio + gpioToGPSET [0]) = pinSet ;
}

void digitalWriteByteSys (int value)
{
  int mask = 1 ;
  int pin ;

  for (pin = 0 ; pin < 8 ; ++pin)
  {
    digitalWriteSys (pinToGpio [pin], value & mask) ;
    mask <<= 1 ;
  }
}


/*
 * pwmWrite:
 *	Set an output PWM value
 *********************************************************************************
 */

void pwmWriteGpio (int pin, int value)
{
  int port ;

  pin  = pin & 63 ;
  port = gpioToPwmPort [pin] ;

  *(pwm + port) = value ;
}

void pwmWriteWPi (int pin, int value)
{
  pwmWriteGpio (pinToGpio [pin & 63], value) ;
}

void pwmWriteSys (int pin, int value)
{
  return ;
}


/*
 * gpioClockSet:
 *	Set the freuency on a GPIO clock pin
 *********************************************************************************
 */

void gpioClockSetGpio (int pin, int freq)
{
  int divi, divr, divf ;

  pin &= 63 ;
  
  divi = 19200000 / freq ;
  divr = 19200000 % freq ;
  divf = (int)((double)divr * 4096.0 / 19200000.0) ;

  if (divi > 4095)
    divi = 4095 ;

  *(clk + gpioToClkCon [pin]) = BCM_PASSWORD | GPIO_CLOCK_SOURCE ;		// Stop GPIO Clock
  while ((*(clk + gpioToClkCon [pin]) & 0x80) != 0)				// ... and wait
    ;

  *(clk + gpioToClkDiv [pin]) = BCM_PASSWORD | (divi << 12) | divf ;		// Set dividers
  *(clk + gpioToClkCon [pin]) = BCM_PASSWORD | 0x10 | GPIO_CLOCK_SOURCE ;	// Start Clock
}

void gpioClockSetWPi (int pin, int freq)
{
  gpioClockSetGpio (pinToGpio [pin & 63], freq) ;
}

void gpioClockSetSys (int pin, int freq)
{
  return ;
}


/*
 * setPadDrive:
 *	Set the PAD driver value
 *********************************************************************************
 */

void setPadDriveWPi (int group, int value)
{
  uint32_t wrVal ;

  if ((group < 0) || (group > 2))
    return ;

  wrVal = BCM_PASSWORD | 0x18 | (value & 7) ;
  *(pads + group + 11) = wrVal ;

  if (wiringPiDebug)
  {
    printf ("setPadDrive: Group: %d, value: %d (%08X)\n", group, value, wrVal) ;
    printf ("Read : %08X\n", *(pads + group + 11)) ;
  }
}

void setPadDriveGpio (int group, int value)
{
  setPadDriveWPi (group, value) ;
}

void setPadDriveSys (int group, int value)
{
  return ;
}


/*
 * digitalRead:
 *	Read the value of a given Pin, returning HIGH or LOW
 *********************************************************************************
 */

int digitalReadWPi (int pin)
{
  pin = pinToGpio [pin & 63] ;

  if ((*(gpio + gpioToGPLEV [pin]) & (1 << (pin & 31))) != 0)
    return HIGH ;
  else
    return LOW ;
}

int digitalReadGpio (int pin)
{
  pin &= 63 ;

  if ((*(gpio + gpioToGPLEV [pin]) & (1 << (pin & 31))) != 0)
    return HIGH ;
  else
    return LOW ;
}

int digitalReadSys (int pin)
{
  char c ;

  pin &= 63 ;

  if (sysFds [pin] == -1)
    return 0 ;

  lseek (sysFds [pin], 0L, SEEK_SET) ;
  read  (sysFds [pin], &c, 1) ;
  return (c == '0') ? 0 : 1 ;
}


/*
 * pullUpDownCtrl:
 *	Control the internal pull-up/down resistors on a GPIO pin
 *	The Arduino only has pull-ups and these are enabled by writing 1
 *	to a port when in input mode - this paradigm doesn't quite apply
 *	here though.
 *********************************************************************************
 */

void pullUpDnControlGpio (int pin, int pud)
{
  pin &= 63 ;
  pud &=  3 ;

  *(gpio + GPPUD)              = pud ;			delayMicroseconds (5) ;
  *(gpio + gpioToPUDCLK [pin]) = 1 << (pin & 31) ;	delayMicroseconds (5) ;
  
  *(gpio + GPPUD)              = 0 ;			delayMicroseconds (5) ;
  *(gpio + gpioToPUDCLK [pin]) = 0 ;			delayMicroseconds (5) ;
}

void pullUpDnControlWPi (int pin, int pud)
{
  pullUpDnControlGpio (pinToGpio [pin & 63], pud) ;
}

void pullUpDnControlSys (int pin, int pud)
{
  return ;
}


/*
 * pinMode:
 *	Sets the mode of a pin to be input, output or PWM output
 *********************************************************************************
 */

void pinModeGpio (int pin, int mode)
{
//  register int barrier ;

  int fSel, shift, alt ;

  pin &= 63 ;

  fSel    = gpioToGPFSEL [pin] ;
  shift   = gpioToShift  [pin] ;

  /**/ if (mode == INPUT)
    *(gpio + fSel) = (*(gpio + fSel) & ~(7 << shift)) ; // Sets bits to zero = input
  else if (mode == OUTPUT)
    *(gpio + fSel) = (*(gpio + fSel) & ~(7 << shift)) | (1 << shift) ;
  else if (mode == PWM_OUTPUT)
  {
    if ((alt = gpioToPwmALT [pin]) == 0)	// Not a PWM pin
      return ;

// Set pin to PWM mode

    *(gpio + fSel) = (*(gpio + fSel) & ~(7 << shift)) | (alt << shift) ;
    delayMicroseconds (110) ;		// See comments in pwmSetClockWPi

    pwmSetModeWPi  (PWM_MODE_BAL) ;	// Pi default mode
    pwmSetRangeWPi (1024) ;		// Default range of 1024
    pwmSetClockWPi (32) ;		// 19.2 / 32 = 600KHz - Also starts the PWM
  }
  else if (mode == GPIO_CLOCK)
  {
    if ((alt = gpioToGpClkALT0 [pin]) == 0)	// Not a GPIO_CLOCK pin
      return ;

// Set pin to GPIO_CLOCK mode and set the clock frequency to 100KHz

    *(gpio + fSel) = (*(gpio + fSel) & ~(7 << shift)) | (alt << shift) ;
    delayMicroseconds (110) ;
    gpioClockSetGpio (pin, 100000) ;
  }
}

void pinModeWPi (int pin, int mode)
{
  pinModeGpio (pinToGpio [pin & 63], mode) ;
}

void pinModeSys (int pin, int mode)
{
  return ;
}


/*
 * waitForInterrupt:
 *	Wait for Interrupt on a GPIO pin.
 *	This is actually done via the /sys/class/gpio interface regardless of
 *	the wiringPi access mode in-use. Maybe sometime it might get a better
 *	way for a bit more efficiency.
 *********************************************************************************
 */

int waitForInterruptSys (int pin, int mS)
{
  int fd, x ;
  uint8_t c ;
  struct pollfd polls ;

  if ((fd = sysFds [pin & 63]) == -1)
    return -2 ;

// Setup poll structure

  polls.fd     = fd ;
  polls.events = POLLPRI ;	// Urgent data!

// Wait for it ...

  x = poll (&polls, 1, mS) ;

// Do a dummy read to clear the interrupt
//	A one character read appars to be enough.

  (void)read (fd, &c, 1) ;

  return x ;
}

int waitForInterruptWPi (int pin, int mS)
{
  return waitForInterruptSys (pinToGpio [pin & 63], mS) ;
}

int waitForInterruptGpio (int pin, int mS)
{
  return waitForInterruptSys (pin, mS) ;
}


/*
 * interruptHandler:
 *	This is a thread and gets started to wait for the interrupt we're
 *	hoping to catch. It will call the user-function when the interrupt
 *	fires.
 *********************************************************************************
 */

static void *interruptHandler (void *arg)
{
  int myPin = *(int *)arg ;

  (void)piHiPri (55) ;	// Only effective if we run as root

  for (;;)
    if (waitForInterruptSys (myPin, -1) > 0)
      isrFunctions [myPin] () ;

  return NULL ;
}


/*
 * wiringPiISR:
 *	Take the details and create an interrupt handler that will do a call-
 *	back to the user supplied function.
 *********************************************************************************
 */

int wiringPiISR (int pin, int mode, void (*function)(void))
{
  pthread_t threadId ;
  char fName   [64] ;
  char *modeS ;
  char  pinS [8] ;
  pid_t pid ;
  int   count, i ;
  uint8_t c ;

  pin &= 63 ;

  if (wiringPiMode == WPI_MODE_UNINITIALISED)
  {
    fprintf (stderr, "wiringPiISR: wiringPi has not been initialised. Unable to continue.\n") ;
    exit (EXIT_FAILURE) ;
  }
  else if (wiringPiMode == WPI_MODE_PINS)
    pin = pinToGpio [pin] ;

// Now export the pin and set the right edge
//	We're going to use the gpio program to do this, so it assumes
//	a full installation of wiringPi. It's a bit 'clunky', but it
//	is a way that will work when we're running in "Sys" mode, as
//	a non-root user. (without sudo)

  if (mode != INT_EDGE_SETUP)
  {
    /**/ if (mode == INT_EDGE_FALLING)
      modeS = "falling" ;
    else if (mode == INT_EDGE_RISING)
      modeS = "rising" ;
    else
      modeS = "both" ;

    sprintf (pinS, "%d", pin) ;

    if ((pid = fork ()) < 0)	// Fail
      return pid ;

    if (pid == 0)	// Child, exec
    {
      execl ("/usr/local/bin/gpio", "gpio", "edge", pinS, modeS, (char *)NULL) ;
      return -1 ;	// Failure ...
    }
    else		// Parent, wait
      wait (NULL) ;
  }

// Now pre-open the /sys/class node - it may already be open if
//	we are in Sys mode, but this will do no harm.

  sprintf (fName, "/sys/class/gpio/gpio%d/value", pin) ;
  if ((sysFds [pin] = open (fName, O_RDWR)) < 0)
    return -1 ;

// Clear any initial pending interrupt

  ioctl (sysFds [pin], FIONREAD, &count) ;
  for (i = 0 ; i < count ; ++i)
    read (sysFds [pin], &c, 1) ;

  isrFunctions [pin] = function ;

  pthread_create (&threadId, NULL, interruptHandler, &pin) ;

  delay (1) ;

  return 0 ;
}


/*
 * initialiseEpoch:
 *	Initialise our start-of-time variable to be the current unix
 *	time in milliseconds.
 *********************************************************************************
 */

static void initialiseEpoch (void)
{
  struct timeval tv ;

  gettimeofday (&tv, NULL) ;
  epochMilli = (uint64_t)tv.tv_sec * (uint64_t)1000    + (uint64_t)(tv.tv_usec / 1000) ;
  epochMicro = (uint64_t)tv.tv_sec * (uint64_t)1000000 + (uint64_t)(tv.tv_usec) ;
}

/*
 * delay:
 *	Wait for some number of milli seconds
 *********************************************************************************
 */

void delay (unsigned int howLong)
{
  struct timespec sleeper, dummy ;

  sleeper.tv_sec  = (time_t)(howLong / 1000) ;
  sleeper.tv_nsec = (long)(howLong % 1000) * 1000000 ;

  nanosleep (&sleeper, &dummy) ;
}


/*
 * delayMicroseconds:
 *	This is somewhat intersting. It seems that on the Pi, a single call
 *	to nanosleep takes some 80 to 130 microseconds anyway, so while
 *	obeying the standards (may take longer), it's not always what we
 *	want!
 *
 *	So what I'll do now is if the delay is less than 100uS we'll do it
 *	in a hard loop, watching a built-in counter on the ARM chip. This is
 *	somewhat sub-optimal in that it uses 100% CPU, something not an issue
 *	in a microcontroller, but under a multi-tasking, multi-user OS, it's
 *	wastefull, however we've no real choice )-:
 *
 *      Plan B: It seems all might not be well with that plan, so changing it
 *      to use gettimeofday () and poll on that instead...
 *********************************************************************************
 */

void delayMicrosecondsHard (unsigned int howLong)
{
  struct timeval tNow, tLong, tEnd ;

  gettimeofday (&tNow, NULL) ;
  tLong.tv_sec  = howLong / 1000000 ;
  tLong.tv_usec = howLong % 1000000 ;
  timeradd (&tNow, &tLong, &tEnd) ;

  while (timercmp (&tNow, &tEnd, <))
    gettimeofday (&tNow, NULL) ;
}

void delayMicroseconds (unsigned int howLong)
{
  struct timespec sleeper ;

  /**/ if (howLong ==   0)
    return ;
  else if (howLong  < 100)
    delayMicrosecondsHard (howLong) ;
  else
  {
    sleeper.tv_sec  = 0 ;
    sleeper.tv_nsec = (long)(howLong * 1000) ;
    nanosleep (&sleeper, NULL) ;
  }
}


/*
 * millis:
 *	Return a number of milliseconds as an unsigned int.
 *********************************************************************************
 */

unsigned int millis (void)
{
  struct timeval tv ;
  uint64_t now ;

  gettimeofday (&tv, NULL) ;
  now  = (uint64_t)tv.tv_sec * (uint64_t)1000 + (uint64_t)(tv.tv_usec / 1000) ;

  return (uint32_t)(now - epochMilli) ;
}


/*
 * micros:
 *	Return a number of microseconds as an unsigned int.
 *********************************************************************************
 */

unsigned int micros (void)
{
  struct timeval tv ;
  uint64_t now ;

  gettimeofday (&tv, NULL) ;
  now  = (uint64_t)tv.tv_sec * (uint64_t)1000000 + (uint64_t)tv.tv_usec ;

  return (uint32_t)(now - epochMicro) ;
}


/*
 * wiringPiSetup:
 *	Must be called once at the start of your program execution.
 *
 * Default setup: Initialises the system into wiringPi Pin mode and uses the
 *	memory mapped hardware directly.
 *********************************************************************************
 */

int wiringPiSetup (void)
{
  int      fd ;
  int      boardRev ;

  if (geteuid () != 0)
  {
    fprintf (stderr, "wiringPi:\n  Must be root to call wiringPiSetup().\n  (Did you forget sudo?)\n") ;
    exit (EXIT_FAILURE) ;
  }

  if (getenv ("WIRINGPI_DEBUG") != NULL)
  {
    printf ("wiringPi: Debug mode enabled\n") ;
    wiringPiDebug = TRUE ;
  }

  if (wiringPiDebug)
    printf ("wiringPi: wiringPiSetup called\n") ;

            pinMode =           pinModeWPi ;
             getAlt =            getAltWPi ;
    pullUpDnControl =   pullUpDnControlWPi ;
       digitalWrite =      digitalWriteWPi ;
   digitalWriteByte = digitalWriteByteGpio ;	// Same code
       gpioClockSet =      gpioClockSetWPi ;
           pwmWrite =          pwmWriteWPi ;
        setPadDrive =       setPadDriveWPi ;
        digitalRead =       digitalReadWPi ;
   waitForInterrupt =  waitForInterruptWPi ;
         pwmSetMode =        pwmSetModeWPi ;
        pwmSetRange =       pwmSetRangeWPi ;
        pwmSetClock =       pwmSetClockWPi ;
  
  boardRev = piBoardRev () ;

  if (boardRev == 1)
    pinToGpio = pinToGpioR1 ;
  else
    pinToGpio = pinToGpioR2 ;

// Open the master /dev/memory device

  if ((fd = open ("/dev/mem", O_RDWR | O_SYNC) ) < 0)
  {
    if (wiringPiDebug)
    {
      int serr = errno ;
	fprintf (stderr, "wiringPiSetup: Unable to open /dev/mem: %s\n", strerror (errno)) ;
      errno = serr ;
    }
    return -1 ;
  }

// GPIO:

  gpio = (uint32_t *)mmap(0, BLOCK_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, GPIO_BASE) ;
  if ((int32_t)gpio == -1)
  {
    if (wiringPiDebug)
    {
      int serr = errno ;
	fprintf (stderr, "wiringPiSetup: mmap failed: %s\n", strerror (errno)) ;
      errno = serr ;
    }
    return -1 ;
  }

// PWM

  pwm = (uint32_t *)mmap(0, BLOCK_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, GPIO_PWM) ;
  if ((int32_t)pwm == -1)
  {
    if (wiringPiDebug)
    {
      int serr = errno ;
	fprintf (stderr, "wiringPiSetup: mmap failed (pwm): %s\n", strerror (errno)) ;
      errno = serr ;
    }
    return -1 ;
  }
 
// Clock control (needed for PWM)

  clk = (uint32_t *)mmap(0, BLOCK_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, CLOCK_BASE) ;
  if ((int32_t)clk == -1)
  {
    if (wiringPiDebug)
    {
      int serr = errno ;
	fprintf (stderr, "wiringPiSetup: mmap failed (clk): %s\n", strerror (errno)) ;
      errno = serr ;
    }
    return -1 ;
  }
 
// The drive pads

  pads = (uint32_t *)mmap(0, BLOCK_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, GPIO_PADS) ;
  if ((int32_t)pads == -1)
  {
    if (wiringPiDebug)
    {
      int serr = errno ;
	fprintf (stderr, "wiringPiSetup: mmap failed (pads): %s\n", strerror (errno)) ;
      errno = serr ;
    }
    return -1 ;
  }

// The system timer

  timer = (uint32_t *)mmap(0, BLOCK_SIZE, PROT_READ|PROT_WRITE, MAP_SHARED, fd, GPIO_TIMER) ;
  if ((int32_t)timer == -1)
  {
    if (wiringPiDebug)
    {
      int serr = errno ;
	fprintf (stderr, "wiringPiSetup: mmap failed (timer): %s\n", strerror (errno)) ;
      errno = serr ;
    }
    return -1 ;
  }

// Set the timer to free-running, 1MHz.
//	0xF9 is 249, the timer divide is base clock / (divide+1)
//	so base clock is 250MHz / 250 = 1MHz.

  *(timer + TIMER_CONTROL) = 0x0000280 ;
  *(timer + TIMER_PRE_DIV) = 0x00000F9 ;
  timerIrqRaw = timer + TIMER_IRQ_RAW ;

  initialiseEpoch () ;

  wiringPiMode = WPI_MODE_PINS ;

  return 0 ;
}


/*
 * wiringPiSetupGpio:
 *	Must be called once at the start of your program execution.
 *
 * GPIO setup: Initialises the system into GPIO Pin mode and uses the
 *	memory mapped hardware directly.
 *********************************************************************************
 */

int wiringPiSetupGpio (void)
{
  int x  ;

  if (geteuid () != 0)
  {
    fprintf (stderr, "Must be root to call wiringPiSetupGpio(). (Did you forget sudo?)\n") ;
    exit (EXIT_FAILURE) ;
  }

  if ((x = wiringPiSetup ()) < 0)
    return x ;

  if (wiringPiDebug)
    printf ("wiringPi: wiringPiSetupGpio called\n") ;

            pinMode =           pinModeGpio ;
             getAlt =            getAltGpio ;
    pullUpDnControl =   pullUpDnControlGpio ;
       digitalWrite =      digitalWriteGpio ;
   digitalWriteByte =  digitalWriteByteGpio ;
       gpioClockSet =      gpioClockSetGpio ;
           pwmWrite =          pwmWriteGpio ;
        setPadDrive =       setPadDriveGpio ;
        digitalRead =       digitalReadGpio ;
   waitForInterrupt =  waitForInterruptGpio ;
         pwmSetMode =        pwmSetModeWPi ;
        pwmSetRange =       pwmSetRangeWPi ;
        pwmSetClock =       pwmSetClockWPi ;

  wiringPiMode = WPI_MODE_GPIO ;

  return 0 ;
}


/*
 * wiringPiSetupSys:
 *	Must be called once at the start of your program execution.
 *
 * Initialisation (again), however this time we are using the /sys/class/gpio
 *	interface to the GPIO systems - slightly slower, but always usable as
 *	a non-root user, assuming the devices are already exported and setup correctly.
 */

int wiringPiSetupSys (void)
{
  int boardRev ;
  int pin ;
  char fName [128] ;

  if (getenv ("WIRINGPI_DEBUG") != NULL)
    wiringPiDebug = TRUE ;

  if (wiringPiDebug)
    printf ("wiringPi: wiringPiSetupSys called\n") ;

            pinMode =           pinModeSys ;
             getAlt =            getAltSys ;
    pullUpDnControl =   pullUpDnControlSys ;
       digitalWrite =      digitalWriteSys ;
   digitalWriteByte =  digitalWriteByteSys ;
       gpioClockSet =      gpioClockSetSys ;
           pwmWrite =          pwmWriteSys ;
        setPadDrive =       setPadDriveSys ;
        digitalRead =       digitalReadSys ;
   waitForInterrupt =  waitForInterruptSys ;
         pwmSetMode =        pwmSetModeSys ;
        pwmSetRange =       pwmSetRangeSys ;
        pwmSetClock =       pwmSetClockSys ;

  boardRev = piBoardRev () ;

  if (boardRev == 1)
    pinToGpio = pinToGpioR1 ;
  else
    pinToGpio = pinToGpioR2 ;

// Open and scan the directory, looking for exported GPIOs, and pre-open
//	the 'value' interface to speed things up for later
  
  for (pin = 0 ; pin < 64 ; ++pin)
  {
    sprintf (fName, "/sys/class/gpio/gpio%d/value", pin) ;
    sysFds [pin] = open (fName, O_RDWR) ;
  }

  initialiseEpoch () ;

  wiringPiMode = WPI_MODE_GPIO_SYS ;

  return 0 ;
}