// Memory Mapped GPIO example
// mmgpio.cpp
// http:elinux.org/RPi_GPIO_Code_Samples
// How to access GPIO registers from C-code on the Raspberry-Pi
// Example program
// 15-January-2012
// Dom and Gert
// Revised: 15-Feb-2013
// Raspberry Pi 1, Raspberry Pi 2, or Raspberry Pi 3
//#define BCM2708_PERI_BASE        0x20000000 /* Pi 1 */

#define BCM2708_PERI_BASE        0x3F000000 /* Pi 2 & Pi 3 */

#define GPIO_BASE                (BCM2708_PERI_BASE + 0x200000) /* GPIO controller */
 
 
#include <stdio.h>
#include <stdlib.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <unistd.h>
 
#define PAGE_SIZE (4*1024)
#define BLOCK_SIZE (4*1024)
 
int  mem_fd;
void *gpio_map;
 
// I/O access
volatile unsigned *gpio;
  
// GPIO setup macros. Always use INP_GPIO(x) before using OUT_GPIO(x) or SET_GPIO_ALT(x,y)
#define INP_GPIO(g) *(gpio+((g)/10)) &= ~(7<<(((g)%10)*3))
#define OUT_GPIO(g) *(gpio+((g)/10)) |=  (1<<(((g)%10)*3))
#define SET_GPIO_ALT(g,a) *(gpio+(((g)/10))) |= (((a)<=3?(a)+4:(a)==4?3:2)<<(((g)%10)*3))
 
#define GPIO_SET *(gpio+7)  // sets   bits which are 1 ignores bits which are 0
#define GPIO_CLR *(gpio+10) // clears bits which are 1 ignores bits which are 0
 
#define GET_GPIO(g) (*(gpio+13)&(1<<g)) // 0 if LOW, (1<<g) if HIGH
 
#define GPIO_PULL *(gpio+37) // Pull up/pull down
#define GPIO_PULLCLK0 *(gpio+38) // Pull up/pull down clock

#define MY_GPIO	4

void setup_io();
 
void printButton(int g)
{
  if (GET_GPIO(g)) // !=0 <-> bit is 1 <- port is HIGH=3.3V
	printf("Button pressed!\n");
  else // port is LOW=0V
	printf("Button released!\n");
}

int main(int argc, char **argv)
{
  int g,rep;
 
  // Set up gpi pointer for direct register access
  setup_io();
 
  // Switch GPIO 7..11 to output mode
 
 /************************************************************************\
  * You are about to change the GPIO settings of your computer.          *
  * Mess this up and it will stop working!                               *
  * It might be a good idea to 'sync' before running this program        *
  * so at least you still have your code changes written to the SD-card! *
 \************************************************************************/
  // Jim's version - gpio 17 only
  INP_GPIO(MY_GPIO); // must use INP_GPIO before we can use OUT_GPIO
  OUT_GPIO(MY_GPIO);

  for (rep=0; rep<10; rep++)
  {
		GPIO_SET = 1<<MY_GPIO;
		sleep(1);
		GPIO_CLR = 1<<MY_GPIO;
		sleep(1);
  }

  return 0;
 
} // main
 
 //
// Set up a memory regions to access GPIO
//
void setup_io()
{
   /* open /dev/mem */
   if ((mem_fd = open("/dev/mem",O_RDWR|O_SYNC) ) < 0) {
	  printf("can't open /dev/mem \n");
	  exit(-1);
   }
 
   /* mmap GPIO */
   gpio_map = mmap(
	  NULL,             //Any adddress in our space will do
	  BLOCK_SIZE,       //Map length
	  PROT_READ|PROT_WRITE,// Enable reading & writting to mapped memory
	  MAP_SHARED,       //Shared with other processes
	  mem_fd,           //File to map
	  GPIO_BASE         //Offset to GPIO peripheral
   );
 
   close(mem_fd); //No need to keep mem_fd open after mmap
 
   if (gpio_map == MAP_FAILED) {
	  printf("mmap error %d\n", (int)gpio_map);//errno also set!
	  exit(-1);
   }
 
   // Always use volatile pointer!
   gpio = (volatile unsigned *)gpio_map;
 
 
} // setup_io

/*
   // GPIO Pull Up/Pull Down Register Example
   
   // enable pull-up on GPIO24&25
   GPIO_PULL = 2;
   short_wait();
   // clock on GPIO 24 & 25 (bit 24 & 25 set)
   GPIO_PULLCLK0 = 0x03000000;
   short_wait();
   GPIO_PULL = 0;
   GPIO_PULLCLK0 = 0;
*/