PX4-Autopilot/src/drivers/linux_pwm_out/navio_sysfs.cpp

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#include "navio_sysfs.h"

#include <fcntl.h>
#include <errno.h>
#include <px4_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;
}