PX4-Autopilot/src/drivers/pps_capture/PPSCapture.cpp

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/**
 * @file PPSCapture.cpp
 *
 * This is driver for capturing GNSS Pulse Per Second (PPS) signal.
 *
 */

#include "PPSCapture.hpp"
#include <px4_arch/io_timer.h>
#include <board_config.h>
#include <parameters/param.h>

#ifdef BOARD_WITH_IO
# define PARAM_PREFIX "PWM_AUX"
#else
# define PARAM_PREFIX "PWM_MAIN"
#endif

PPSCapture::PPSCapture() :
	ScheduledWorkItem(MODULE_NAME, px4::wq_configurations::hp_default)
{
	_pps_capture_pub.advertise();
}

PPSCapture::~PPSCapture()
{
	if (_channel >= 0) {
		io_timer_unallocate_channel(_channel);
		px4_arch_gpiosetevent(_pps_capture_gpio, false, false, false, nullptr, nullptr);
	}
}

bool PPSCapture::init()
{
	bool success = false;

	param_t p_ctrl_alloc = param_find("SYS_CTRL_ALLOC");
	int32_t ctrl_alloc = 0;

	if (p_ctrl_alloc != PARAM_INVALID) {
		param_get(p_ctrl_alloc, &ctrl_alloc);
	}

	if (ctrl_alloc == 1) {

		for (unsigned i = 0; i < 16; ++i) {
			char param_name[17];
			snprintf(param_name, sizeof(param_name), "%s_%s%d", PARAM_PREFIX, "FUNC", i + 1);
			param_t function_handle = param_find(param_name);
			int32_t function;

			if (function_handle != PARAM_INVALID && param_get(function_handle, &function) == 0) {
				if (function == 2064) { // PPS_Input
					_channel = i;
				}
			}
		}
	}

#if defined(PPS_CAPTURE_CHANNEL)

	if (_channel == -1) {
		_channel = PPS_CAPTURE_CHANNEL;
	}

#endif

	if (_channel == -1) {
		PX4_WARN("No pps channel configured");
		return false;
	}

	int ret = io_timer_allocate_channel(_channel, IOTimerChanMode_PPS);

	if (ret != PX4_OK) {
		PX4_ERR("gpio alloc failed (%i) for PPS at channel (%d)", ret, _channel);
		return false;
	}

	_pps_capture_gpio = PX4_MAKE_GPIO_EXTI(io_timer_channel_get_as_pwm_input(_channel));
	int ret_val = px4_arch_gpiosetevent(_pps_capture_gpio, true, false, true, &PPSCapture::gpio_interrupt_callback, this);

	if (ret_val == PX4_OK) {
		success = true;
	}

	return success;
}

void PPSCapture::Run()
{
	if (should_exit()) {
		exit_and_cleanup();
		return;
	}

	sensor_gps_s sensor_gps;

	if (_sensor_gps_sub.update(&sensor_gps)) {
		_last_gps_utc_timestamp = sensor_gps.time_utc_usec;
		_last_gps_timestamp = sensor_gps.timestamp;
	}

	pps_capture_s pps_capture;
	pps_capture.timestamp = _hrt_timestamp;
	// GPS UTC time when the GPIO interrupt was triggered
	// Last UTC time received from the GPS + elapsed time to the PPS interrupt
	uint64_t gps_utc_time = _last_gps_utc_timestamp + (_hrt_timestamp - _last_gps_timestamp);

	// (For ubx F9P) The rising edge of the PPS pulse is aligned to the top of second GPS time base.
	// So, remove the fraction of second and shift to the next second. The interrupt is triggered
	// before the matching timestamp is received via a UART message, which means the last received GPS time is always
	// behind.
	pps_capture.rtc_timestamp = gps_utc_time - (gps_utc_time % USEC_PER_SEC) + USEC_PER_SEC;

	_pps_capture_pub.publish(pps_capture);
}

int PPSCapture::gpio_interrupt_callback(int irq, void *context, void *arg)
{
	PPSCapture *instance = static_cast<PPSCapture *>(arg);

	instance->_hrt_timestamp = hrt_absolute_time();
	instance->ScheduleNow(); // schedule work queue to publish PPS captured time

	return PX4_OK;
}

int PPSCapture::task_spawn(int argc, char *argv[])
{
	PPSCapture *instance = new PPSCapture();

	if (instance) {
		_object.store(instance);
		_task_id = task_id_is_work_queue;

		if (instance->init()) {
			return PX4_OK;
		}

	} else {
		PX4_ERR("alloc failed");
	}

	delete instance;
	_object.store(nullptr);
	_task_id = -1;

	return PX4_ERROR;
}

int PPSCapture::custom_command(int argc, char *argv[])
{
	return print_usage("unknown command");
}

int PPSCapture::print_usage(const char *reason)
{
	if (reason) {
		PX4_WARN("%s\n", reason);
	}

	PRINT_MODULE_DESCRIPTION(
		R"DESCR_STR(
### Description
This implements capturing PPS information from the GNSS module and calculates the drift between PPS and Real-time clock.

)DESCR_STR");

	PRINT_MODULE_USAGE_NAME("pps_capture", "driver");
	PRINT_MODULE_USAGE_COMMAND("start");
	PRINT_MODULE_USAGE_DEFAULT_COMMANDS();

	return 0;
}

void PPSCapture::stop()
{
	exit_and_cleanup();
}

extern "C" __EXPORT int pps_capture_main(int argc, char *argv[])
{
	if (argc >= 2 && !strcmp(argv[1], "stop") && PPSCapture::is_running()) {
		PPSCapture::stop();
	}

	return PPSCapture::main(argc, argv);
}