navio_sysfs.cpp

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#include "navio_sysfs.h"

#include <fcntl.h>
#include <errno.h>
#include <unistd.h>
#include <px4_platform_common/log.h>

using namespace linux_pwm_out;

NavioSysfsPWMOut::NavioSysfsPWMOut(const char *device, int max_num_outputs)
    : _device(device)
{
    if (max_num_outputs > MAX_NUM_PWM) {
        PX4_WARN("number of outputs too large. Setting to %i", MAX_NUM_PWM);
        max_num_outputs = MAX_NUM_PWM;
    }

    for (int i = 0; i < MAX_NUM_PWM; ++i) {
        _pwm_fd[i] = -1;
    }

    _pwm_num = max_num_outputs;
}

NavioSysfsPWMOut::~NavioSysfsPWMOut()
{
    for (int i = 0; i < MAX_NUM_PWM; ++i) {
        if (_pwm_fd[i] != -1) {
            ::close(_pwm_fd[i]);
        }
    }
}

int NavioSysfsPWMOut::init()
{
    int i;
    char path[128];

    for (i = 0; i < _pwm_num; ++i) {
        ::snprintf(path, sizeof(path), "%s/export", _device);

        if (pwm_write_sysfs(path, i) < 0) {
            PX4_ERR("PWM export failed");
        }
    }

    for (i = 0; i < _pwm_num; ++i) {
        ::snprintf(path, sizeof(path), "%s/pwm%u/enable", _device, i);

        if (pwm_write_sysfs(path, 1) < 0) {
            PX4_ERR("PWM enable failed");
        }
    }

    for (i = 0; i < _pwm_num; ++i) {
        ::snprintf(path, sizeof(path), "%s/pwm%u/period", _device, i);

        if (pwm_write_sysfs(path, (int)1e9 / FREQUENCY_PWM)) {
            PX4_ERR("PWM period failed");
        }
    }

    for (i = 0; i < _pwm_num; ++i) {
        ::snprintf(path, sizeof(path), "%s/pwm%u/duty_cycle", _device, i);
        _pwm_fd[i] = ::open(path, O_WRONLY | O_CLOEXEC);

        if (_pwm_fd[i] == -1) {
            PX4_ERR("PWM: Failed to open duty_cycle.");
            return -errno;
        }
    }

    return 0;
}

int NavioSysfsPWMOut::send_output_pwm(const uint16_t *pwm, int num_outputs)
{
    char data[16];

    if (num_outputs > _pwm_num) {
        num_outputs = _pwm_num;
    }

    int ret = 0;

    //convert this to duty_cycle in ns
    for (int i = 0; i < num_outputs; ++i) {
        int n = ::snprintf(data, sizeof(data), "%u", pwm[i] * 1000);
        int write_ret = ::write(_pwm_fd[i], data, n);

        if (n != write_ret) {
            ret = -1;
        }
    }

    return ret;
}

int NavioSysfsPWMOut::pwm_write_sysfs(char *path, int value)
{
    int fd = ::open(path, O_WRONLY | O_CLOEXEC);
    int n;
    char data[16];

    if (fd == -1) {
        return -errno;
    }

    n = ::snprintf(data, sizeof(data), "%u", value);

    if (n > 0) {
        n = ::write(fd, data, n);   // This n is not used, but to avoid a compiler error.
    }

    ::close(fd);

    return 0;
}