【NanoPi NEO/Armbian】PWMを使い圧電ブザーでメロディを奏でてみる

#include <stdio.h>
#include <sys/types.h>
#include <sys/stat.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>
#include <stdlib.h>
#include <time.h>

#define BPM               (80LLU)
#define NSEC              (1000000000LLU)
#define WHOLENOTETIME     ((60LLU * NSEC) / BPM * 4LLU)

const unsigned long periodTbl[] = {
    2272727,    // 440.000 a4
    2024771,    // 493.883 b4
    3822250,    // 261.626 c4
    3405241,    // 293.665 d4
    3033723,    // 329.628 e4
    2863459,    // 349.228 f4
    2551053     // 391.995 g4
};

static void noteout( unsigned long period, unsigned long timensec )
{
    int fd = -1;
    int ret;
    struct stat st = { 0 };
    unsigned long periodValue;
    unsigned long dutyValue;
    char valueStr[16];
    int strSize;
    struct timespec tms;
    struct timespec tms_before;
    struct timespec tms_after;
    unsigned long long timensec_adjustment;

    if( period == 0U ) {
        return;
    }

    printf("[DEBUG]period=%lu, timensec=%lu\n", period, timensec );

    clock_gettime(CLOCK_MONOTONIC, &tms_before);

    // Set period value.
    fd = open("/sys/class/pwm/pwmchip0/pwm0/period",O_RDWR);
    periodValue = period;
    strSize = snprintf(valueStr ,16, "%lu", periodValue);
    if(write(fd, valueStr, strSize) != strSize) {
        perror("write-5");
        exit(EXIT_FAILURE);
    }
    close(fd);

    // Set duty cycle value.
    fd = open("/sys/class/pwm/pwmchip0/pwm0/duty_cycle",O_RDWR);
    dutyValue = period / 2U;
    strSize = snprintf(valueStr, 16, "%lu", dutyValue);
    if(write(fd, valueStr, strSize) != strSize) {
        perror("write-6");
        exit(EXIT_FAILURE);
    }
    close(fd);

    // Set pwm0 enable.
    fd = open("/sys/class/pwm/pwmchip0/pwm0/enable",O_WRONLY);
    if(write(fd, "1", 1) != 1) {
        perror("write-7");
        exit(EXIT_FAILURE);
    }
    close(fd);

    clock_gettime(CLOCK_MONOTONIC, &tms_after);

    timensec_adjustment = timensec - ((tms_after.tv_sec * NSEC + tms_after.tv_nsec)
                          - (tms_before.tv_sec * NSEC + tms_before.tv_nsec)) - 7500U;

    tms.tv_sec = timensec_adjustment / NSEC;
    tms.tv_nsec = timensec_adjustment % NSEC;
    nanosleep(&tms, NULL);

    // Set pwm0 disable.
    fd = open("/sys/class/pwm/pwmchip0/pwm0/enable",O_WRONLY);
    if(write(fd, "0", 1) != 1) {
        perror("write-8");
        exit(EXIT_FAILURE);
    }
    close(fd);

    tms.tv_sec = 0U;
    tms.tv_nsec = 7500U;
    nanosleep(&tms, NULL);

    return;
}

static unsigned long getPeriod( char pitch )
{
    return periodTbl[pitch - 'a'];
}

static unsigned long getTime( unsigned long number )
{
    return WHOLENOTETIME / number;
}

static void mmlplay( const char *mml )
{
    const char *p = mml;
    unsigned long period = 0U;
    unsigned long timensec = 0U;
    unsigned long number = 0U;

    timensec = getTime ( 4U );
    while( *p != '\0' ) {
        if( *p >= 'a' && *p <= 'g' ) {
            noteout( period, timensec );
            period = getPeriod( *p );
            number = 0U;
            timensec = getTime ( 4U );
        } else if( *p >= '0' && *p <= '9' ) {
            number = number * 10U + *p - '0';
            timensec = getTime ( number );
        }
        p++;
    }
    noteout( period, timensec );
    return;
}

int main()
{
    int fd = -1;
    int ret;
    struct stat st = { 0 };
    unsigned long periodValue;
    unsigned long dutyValue;
    char valueStr[16];
    int strSize;

    // Unexport pwm0 if it exists.
    ret = stat("/sys/class/pwm/pwmchip0/pwm0", &st);
    if(ret == 0) {
        fd = open("/sys/class/pwm/pwmchip0/unexport",O_WRONLY);
        if(write(fd, "0", 1) != 1) {
            perror("write-1");
            exit(EXIT_FAILURE);
        }
        close(fd);
    }

    // Export pwm0.
    fd = open("/sys/class/pwm/pwmchip0/export",O_WRONLY);
    if(write(fd, "0", 1) != 1) {
        perror("write-3");
        exit(EXIT_FAILURE);
    }
    close(fd);

    // Set pwm0 disable.
    fd = open("/sys/class/pwm/pwmchip0/pwm0/enable",O_WRONLY);
    if(write(fd, "0", 1) != 1) {
        perror("write-2");
        exit(EXIT_FAILURE);
    }
    close(fd);

    // Set polarity to normal.
    fd = open("/sys/class/pwm/pwmchip0/pwm0/polarity",O_WRONLY);
    if(write(fd, "normal", 6) != 6) {
        perror("write-4");
        exit(EXIT_FAILURE);
    }
    close(fd);

    sleep(1);

    mmlplay( "gee2fdd2cdefggg2" );
    mmlplay( "geeefdddceggeee2" );
    mmlplay( "dddddef2eeeeefg2" );
    mmlplay( "geeefdd2ceggeee2" );
    
    exit(EXIT_SUCCESS);
}