px4-firmware/apps/px4io/mixer.cpp

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 *
 *   Copyright (C) 2012 PX4 Development Team. All rights reserved.
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 * modification, are permitted provided that the following conditions
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/**
 * @file mixer.cpp
 *
 * Control channel input/output mixer and failsafe.
 */

#include <nuttx/config.h>
#include <syslog.h>

#include <sys/types.h>
#include <stdbool.h>
#include <string.h>

#include <drivers/drv_pwm_output.h>
#include <drivers/drv_hrt.h>

#include <systemlib/mixer/mixer.h>

extern "C" {
//#define DEBUG
#include "px4io.h"
}

/*
 * Maximum interval in us before FMU signal is considered lost
 */
#define FMU_INPUT_DROP_LIMIT_US		200000

/* XXX need to move the RC_CHANNEL_FUNCTION out of rc_channels.h and into systemlib */
#define ROLL     0
#define PITCH    1
#define YAW      2
#define THROTTLE 3
#define OVERRIDE 4

/* current servo arm/disarm state */
static bool mixer_servos_armed = false;

/* selected control values and count for mixing */
enum mixer_source {
	MIX_NONE,
	MIX_FMU,
	MIX_OVERRIDE,
	MIX_FAILSAFE
};
static mixer_source source;

static int	mixer_callback(uintptr_t handle,
			       uint8_t control_group,
			       uint8_t control_index,
			       float &control);

static MixerGroup mixer_group(mixer_callback, 0);

void
mixer_tick(void)
{
	/* check that we are receiving fresh data from the FMU */
	if (hrt_elapsed_time(&system_state.fmu_data_received_time) > FMU_INPUT_DROP_LIMIT_US) {

		/* too long without FMU input, time to go to failsafe */
		if (r_status_flags & PX4IO_P_STATUS_FLAGS_FMU_OK) {
			lowsyslog("AP RX timeout");
		}
		r_status_flags &= ~(PX4IO_P_STATUS_FLAGS_FMU_OK | PX4IO_P_STATUS_FLAGS_RAW_PWM);
		r_status_alarms |= PX4IO_P_STATUS_ALARMS_FMU_LOST;

		/* XXX this is questionable - vehicle may not make sense for direct control */
		r_status_flags |= PX4IO_P_STATUS_FLAGS_OVERRIDE;
	} else {
		r_status_flags |= PX4IO_P_STATUS_FLAGS_FMU_OK;
		r_status_alarms &= ~PX4IO_P_STATUS_ALARMS_FMU_LOST;
	}

	source = MIX_FAILSAFE;

	/*
	 * Decide which set of controls we're using.
	 */
	if ((r_status_flags & PX4IO_P_STATUS_FLAGS_RAW_PWM) ||
		!(r_status_flags & PX4IO_P_STATUS_FLAGS_MIXER_OK)) {

		/* don't actually mix anything - we already have raw PWM values or
		 not a valid mixer. */
		source = MIX_NONE;

	} else {

		if (!(r_status_flags & PX4IO_P_STATUS_FLAGS_OVERRIDE) &&
		     (r_status_flags & PX4IO_P_STATUS_FLAGS_MIXER_OK)) {

			/* mix from FMU controls */
			source = MIX_FMU;
		}

		if ( (r_status_flags & PX4IO_P_STATUS_FLAGS_OVERRIDE) &&
		     (r_status_flags & PX4IO_P_STATUS_FLAGS_RC_OK) &&
		     (r_status_flags & PX4IO_P_STATUS_FLAGS_MIXER_OK)) {

		 	/* if allowed, mix from RC inputs directly */
			source = MIX_OVERRIDE;
		}
	}

	/*
	 * Run the mixers.
	 */
	if (source == MIX_FAILSAFE) {

		/* copy failsafe values to the servo outputs */
		for (unsigned i = 0; i < IO_SERVO_COUNT; i++)
			r_page_servos[i] = r_page_servo_failsafe[i];

	} else if (source != MIX_NONE) {

		float	outputs[IO_SERVO_COUNT];
		unsigned mixed;

		/* mix */
		mixed = mixer_group.mix(&outputs[0], IO_SERVO_COUNT);

		/* scale to PWM and update the servo outputs as required */
		for (unsigned i = 0; i < mixed; i++) {

			/* save actuator values for FMU readback */
			r_page_actuators[i] = FLOAT_TO_REG(outputs[i]);

			/* scale to servo output */
			r_page_servos[i] = (outputs[i] * 500.0f) + 1500;

		}
		for (unsigned i = mixed; i < IO_SERVO_COUNT; i++)
			r_page_servos[i] = 0;
	}

	/*
	 * Decide whether the servos should be armed right now.
	 *
	 * We must be armed, and we must have a PWM source; either raw from
	 * FMU or from the mixer.
	 *
	 * XXX correct behaviour for failsafe may require an additional case
	 * here.
	 */
	bool should_arm = (
	    /* FMU is armed */ (r_setup_arming & PX4IO_P_SETUP_ARMING_ARM_OK) &&
	 	/* IO is armed */  (r_status_flags & PX4IO_P_STATUS_FLAGS_ARMED) &&
		/* there is valid input */ (r_status_flags & (PX4IO_P_STATUS_FLAGS_RAW_PWM | PX4IO_P_STATUS_FLAGS_MIXER_OK)) &&
		/* IO initialised without error */  (r_status_flags & PX4IO_P_STATUS_FLAGS_INIT_OK));

	if (should_arm && !mixer_servos_armed) {
		/* need to arm, but not armed */
		up_pwm_servo_arm(true);
		mixer_servos_armed = true;

	} else if (!should_arm && mixer_servos_armed) {
		/* armed but need to disarm */
		up_pwm_servo_arm(false);
		mixer_servos_armed = false;
	}

	if (mixer_servos_armed) {
		/* update the servo outputs. */
		for (unsigned i = 0; i < IO_SERVO_COUNT; i++)
			up_pwm_servo_set(i, r_page_servos[i]);
	}
}

static int
mixer_callback(uintptr_t handle,
	       uint8_t control_group,
	       uint8_t control_index,
	       float &control)
{
	if (control_group != 0)
		return -1;

	switch (source) {
	case MIX_FMU:
		if (control_index < PX4IO_CONTROL_CHANNELS) {
			control = REG_TO_FLOAT(r_page_controls[control_index]);
			break;
		}
		return -1;

	case MIX_OVERRIDE:
		if (r_page_rc_input[PX4IO_P_RC_VALID] & (1 << control_index)) {
			control = REG_TO_FLOAT(r_page_rc_input[PX4IO_P_RC_BASE + control_index]);
			break;
		}
		return -1;

	case MIX_FAILSAFE:
	case MIX_NONE:
		/* XXX we could allow for configuration of per-output failsafe values */
		return -1;
	}

	return 0;
}

/*
 * XXX error handling here should be more aggressive; currently it is
 * possible to get STATUS_FLAGS_MIXER_OK set even though the mixer has
 * not loaded faithfully.
 */

static char mixer_text[256];		/* large enough for one mixer */
static unsigned mixer_text_length = 0;

void
mixer_handle_text(const void *buffer, size_t length)
{
	/* do not allow a mixer change while fully armed */
	if (/* FMU is armed */ (r_setup_arming & PX4IO_P_SETUP_ARMING_ARM_OK) &&
	    /* IO is armed */  (r_status_flags & PX4IO_P_STATUS_FLAGS_ARMED)) {
		return;
	}

	px4io_mixdata	*msg = (px4io_mixdata *)buffer;

	isr_debug(2, "mix txt %u", length);

	if (length < sizeof(px4io_mixdata))
		return;

	unsigned	text_length = length - sizeof(px4io_mixdata);

	switch (msg->action) {
	case F2I_MIXER_ACTION_RESET:
		isr_debug(2, "reset");

		/* FIRST mark the mixer as invalid */
		r_status_flags &= ~PX4IO_P_STATUS_FLAGS_MIXER_OK;
		/* THEN actually delete it */
		mixer_group.reset();
		mixer_text_length = 0;

		/* FALLTHROUGH */
	case F2I_MIXER_ACTION_APPEND:
		isr_debug(2, "append %d", length);

		/* check for overflow - this is really fatal */
		/* XXX could add just what will fit & try to parse, then repeat... */
		if ((mixer_text_length + text_length + 1) > sizeof(mixer_text)) {
			r_status_flags &= ~PX4IO_P_STATUS_FLAGS_MIXER_OK;
			return;
		}

		/* append mixer text and nul-terminate */
		memcpy(&mixer_text[mixer_text_length], msg->text, text_length);
		mixer_text_length += text_length;
		mixer_text[mixer_text_length] = '\0';
		isr_debug(2, "buflen %u", mixer_text_length);

		/* process the text buffer, adding new mixers as their descriptions can be parsed */
		unsigned resid = mixer_text_length;
		mixer_group.load_from_buf(&mixer_text[0], resid);

		/* if anything was parsed */
		if (resid != mixer_text_length) {

			/* ideally, this should test resid == 0 ? */
			r_status_flags |= PX4IO_P_STATUS_FLAGS_MIXER_OK;

			isr_debug(2, "used %u", mixer_text_length - resid);

			/* copy any leftover text to the base of the buffer for re-use */
			if (resid > 0)
				memcpy(&mixer_text[0], &mixer_text[mixer_text_length - resid], resid);

			mixer_text_length = resid;
		}

		break;
	}
}