/*
    GPIOCPP version 0.09, march 18, 2017 COPYLEFT - Pieter Suurmond.
*/
#include <sys/mman.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
/*                          // Only necessary if you uncomment perror()s below.
#include <cstdio>           // Otherwise, we never write to stderr or stdout,
#include <cerrno>           // instead, we throw an exception in case of error.
*/
#include "gpiocpp.h"        // Also includes <cstdint>.

GPIOCPP::GPIOCPP(uint8_t     model,             // 1 or 2.
                 const char* path)              // "/dev/mem" or "/dev/gpiomem".
                 : blocksize(4*1024)
{
    int         fd;
    uint32_t    base_address;

    if (model == 1)
        base_address = 0x20000000;              // Model 1 = ARMv6.
    else
        base_address = 0x3F000000;              // Model 2 = ARMv7.
    base_address += 0x200000;                   // Start of GPIO controller.

    if ((fd = open(path, O_RDWR | O_SYNC) ) < 0) {
        //perror("GPIOCPP() open()");           // Writes to stderr!
        throw "GPIOCPP() failed to open character device.\n";
    }
    address = static_cast<uint32_t*>(mmap(NULL, blocksize,
                                     PROT_READ | PROT_WRITE, MAP_SHARED,
                                     fd, base_address));
    if (address == MAP_FAILED) {
        //perror("GPIOCPP() mmap()");           // Writes to stderr!
        throw "GPIOCPP() mmap() = MAP_FAILED.\n";
    }
    close(fd);
}

GPIOCPP::~GPIOCPP()
{
    munmap((void*)address, blocksize);
}   // When address is volatile, static_cast seems not possible. Munmap() may
    // fail but destructors in C++ are not allowed to throw.

void GPIOCPP::config_pull(uint8_t pin, PULL pull)
{
    // Address offsets (in bytes/4). See BCM2835-ARM-Peripherals.pdf, p91-100:
    #define GPPUD       (37)
    #define GPPUDCLK0   (38)

    // Would be nice if the following routine is never interrupted. Even slight-
    // ly different timing may give unpredictable results! BCM recommends pauses
    // of 150 cycles (of what?!). 10 us around [GPPUDCLK0] seems to work best.
    usleep(100000);             // 100 milliseconds (BCM does not mention this).
    address[GPPUD] = static_cast<uint32_t>(pull);
    usleep(10);                             // 10 microseconds (see bcm2835.c
    address[GPPUDCLK0] = 1 << pin;          // from Mike McCauley: also 10us).
    usleep(10);                             // 10 microseconds.
    address[GPPUD] = static_cast<uint32_t>(PULL::OFF);
    address[GPPUDCLK0] = 0;
    usleep(100000);             // 100 milliseconds (BCM does not mention this).
}