LinuxTest1.c

/*
 * LinuxTest1.c
 *
 *  Created on: Dec 13, 2016
 *      Author: paul
 */
#include <stdio.h>
#include <unistd.h>
#include <fcntl.h>
#include <sys/mman.h>
#include <pthread.h>


#define HW_REGS_BASE ( 0xff200000 )
#define HW_REGS_SPAN ( 0x00200000 )
#define HW_REGS_MASK ( HW_REGS_SPAN - 1 )
#define RED_LEDS_OFFSET 0x20
#define HEX1_OFFSET 0x30
#define HEX2_OFFSET 0x40
#define HEX3_OFFSET 0x50

void *update(unsigned int * location){
	int k;
	for(k = 0; k <10; k++){
		*location = *location + 1;
		sleep(1);
	}
}

int main(void)
{
	unsigned int *Red_Leds = NULL;
	unsigned int *HEX1 = NULL;
	unsigned int *HEX2 = NULL;
	unsigned int *HEX3 = NULL;
	void *virtual_base;
	int fd;

	// Open memory as if it were a device for read and write access
	if( ( fd = open( "/dev/mem", ( O_RDWR | O_SYNC ) ) ) == -1 ) {
		printf( "ERROR: could not open \"/dev/mem\"...\n" );
		return( 1 );
	}

	// map 2Mbyte of memory starting at 0xFF200000 to user space
	virtual_base = mmap( NULL, HW_REGS_SPAN, ( PROT_READ | PROT_WRITE ),MAP_SHARED, fd, HW_REGS_BASE );

	if( virtual_base == MAP_FAILED ) {
		printf( "ERROR: mmap() failed...\n" );
		close( fd );
		return(1);
	}

	// Get the address that maps to the LEDs
	Red_Leds =(unsigned int *)(virtual_base + (( RED_LEDS_OFFSET ) & (HW_REGS_MASK ) ));
	HEX1 =(unsigned int *)(virtual_base + (( HEX1_OFFSET ) & (HW_REGS_MASK ) ));
	HEX2 =(unsigned int *)(virtual_base + (( HEX2_OFFSET ) & (HW_REGS_MASK ) ));
	HEX3 =(unsigned int *)(virtual_base + (( HEX3_OFFSET ) & (HW_REGS_MASK ) ));
	pthread_t thread1;
	pthread_t thread2;
	pthread_t thread3;
	pthread_t thread4;
	pthread_create(&thread1,NULL, update,Red_Leds);
	pthread_create(&thread2,NULL, update,HEX1);
	pthread_create(&thread3,NULL, update,HEX2);
	pthread_create(&thread4,NULL, update,HEX3);
	pthread_join(thread1,NULL);
	pthread_join(thread2,NULL);
	pthread_join(thread3,NULL);
	pthread_join(thread4,NULL);

	char read[20];
	FILE* openFile = fopen("/home/root/word.txt","w+");
	fputs("Hello World",openFile);
	fclose(openFile);
	openFile = fopen("/home/root/word.txt","r");
	fgets(read, 20, (FILE*)openFile);
	printf("%s\n", read );
	fclose(openFile);


	// when finished, unmap the virtual space and close the memory "device"
	if( munmap( virtual_base, HW_REGS_SPAN ) != 0 ) {
		printf( "ERROR: munmap() failed...\n" );
		close( fd );
		return( 1 );
	}
	close( fd );
	return 0;
}