main.cpp

#include "main.h"

unsigned long int *regAddress = nullptr;
unsigned long int regVal;

int main( int argc, char *argv[] )
{
    regAddress = setRegistryAddress();

    std::string in;
    while ( true )
    {
        std::cin >> in;

        if ( in == "1" )
        {
            pinSet( LED_WHITE );
            continue;
        }

        pinClear( LED_WHITE );
    }
}

unsigned long int *setRegistryAddress()
{
    unsigned long int *registryAddress;

    int memory = open( "/dev/mem", O_RDWR );
    registryAddress = (unsigned long *) mmap(
            NULL,
            REGISTER_BLOCK_SIZE,
            PROT_READ | PROT_WRITE,
            MAP_SHARED,
            memory,
            REGISTER_BLOCK_ADDR
    );
    close( memory );

    return registryAddress;
}

void pinClear( int pin )
{
    SETBIT( regVal, pin, 1 );
    WRITEREG( REGISTER_OE_OFFSET, regVal );
    WRITEREG( REGISTER_CLEAR_OFFSET, ( 0x1 << pin ));
}

void pinSet( int pin )
{
    SETBIT( regVal, LED_WHITE, 1 );
    WRITEREG( REGISTER_OE_OFFSET, regVal );
    WRITEREG( REGISTER_SET_OFFSET, ( 0x1 << pin ));
}

main.h

#ifndef ONIONTEST_MAIN_H
#define ONIONTEST_MAIN_H

#include <unistd.h>
#include <mhash.h>
#include <fcntl.h>
#include <iostream>

#define LED_WHITE 1
#define LED_RED 17
#define LED_GREEN 16
#define LED_BLUE 15

#define REGISTER_BLOCK_ADDR     0x18040000
#define REGISTER_BLOCK_SIZE     0x30
#define REGISTER_OE_OFFSET      0
#define REGISTER_IN_OFFSET      1
#define REGISTER_OUT_OFFSET     2
#define REGISTER_SET_OFFSET     3
#define REGISTER_CLEAR_OFFSET   4

#define WRITEREG( regOff, regVal ) (*(regAddress + regOff) = regVal)
#define READREG( regVal, regOff ) (regVal = *(regAddress + regOff))
#define SETBIT( regVal, bit, val ) (regVal ^= (-val ^ regVal) & (1 << bit))
#define GETBIT( regval, bit ) ((regval >> bit) & 0x1)

void pinSet( int pin );
void pinClear( int pin );
unsigned long int *setRegistryAddress();

#endif //ONIONTEST_MAIN_H