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Use UTM_GLOBAL_POSITION for collision avoidance #12452

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merged 2 commits into from
Jul 16, 2019
Merged

Use UTM_GLOBAL_POSITION for collision avoidance #12452

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a289d2c
Added message handler for UTM_GLOBAL_POSITION
Jul 10, 2019
6c04e9a
Fixed overflowing tslc.
Jul 10, 2019
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76 changes: 76 additions & 0 deletions src/modules/mavlink/mavlink_receiver.cpp
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Original file line number Diff line number Diff line change
Expand Up @@ -202,6 +202,10 @@ MavlinkReceiver::handle_message(mavlink_message_t *msg)
handle_message_adsb_vehicle(msg);
break;

case MAVLINK_MSG_ID_UTM_GLOBAL_POSITION:
handle_message_utm_global_position(msg);
break;

case MAVLINK_MSG_ID_COLLISION:
handle_message_collision(msg);
break;
Expand Down Expand Up @@ -2264,6 +2268,78 @@ MavlinkReceiver::handle_message_adsb_vehicle(mavlink_message_t *msg)
}
}

void
MavlinkReceiver::handle_message_utm_global_position(mavlink_message_t *msg)
{
mavlink_utm_global_position_t utm_pos{};
transponder_report_s t{};

mavlink_msg_utm_global_position_decode(msg, &utm_pos);

// Convert cm/s to m/s
float vx = utm_pos.vx / 100.0f;
float vy = utm_pos.vy / 100.0f;
float vz = utm_pos.vz / 100.0f;

t.timestamp = hrt_absolute_time();
// TODO: ID
t.lat = utm_pos.lat * 1e-7;
t.lon = utm_pos.lon * 1e-7;
t.altitude = utm_pos.alt / 1000.0f;
t.altitude_type = ADSB_ALTITUDE_TYPE_GEOMETRIC;
// UTM_GLOBAL_POSIION uses NED (north, east, down) coordinates for velocity, in cm / s.
t.heading = atan2f(vy, vx);
t.hor_velocity = sqrtf(vy * vy + vx * vx);
t.ver_velocity = -vz;
// TODO: Callsign
// For now, set it to all 0s. This is a null-terminated string, so not explicitly giving it a null
// terminator could cause problems.
memset(&t.callsign[0], 0, sizeof(t.callsign));
t.emitter_type = ADSB_EMITTER_TYPE_NO_INFO; // TODO: Is this correct?

// The Mavlink docs do not specify what to do if tslc (time since last communication) is out of range of
// an 8-bit int, or if this is the first communication.
// Here, I assume that if this is the first communication, tslc = 0.
// If tslc > 255, then tslc = 255.
unsigned long time_passed = (t.timestamp - _last_utm_global_pos_com) / 1000000;

if (_last_utm_global_pos_com == 0) {
time_passed = 0;

} else if (time_passed > UINT8_MAX) {
time_passed = UINT8_MAX;
}

t.tslc = (uint8_t) time_passed;

t.flags = 0;

if (utm_pos.flags | UTM_DATA_AVAIL_FLAGS_POSITION_AVAILABLE) {
t.flags |= transponder_report_s::PX4_ADSB_FLAGS_VALID_COORDS;
}

if (utm_pos.flags | UTM_DATA_AVAIL_FLAGS_ALTITUDE_AVAILABLE) {
t.flags |= transponder_report_s::PX4_ADSB_FLAGS_VALID_ALTITUDE;
}

if (utm_pos.flags | UTM_DATA_AVAIL_FLAGS_HORIZONTAL_VELO_AVAILABLE) {
t.flags |= transponder_report_s::PX4_ADSB_FLAGS_VALID_HEADING;
t.flags |= transponder_report_s::PX4_ADSB_FLAGS_VALID_VELOCITY;
}

// Note: t.flags has deliberately NOT set VALID_CALLSIGN or VALID_SQUAWK, because UTM_GLOBAL_POSITION does not
// provide these.

if (_transponder_report_pub == nullptr) {
_transponder_report_pub = orb_advertise_queue(ORB_ID(transponder_report), &t, transponder_report_s::ORB_QUEUE_LENGTH);

} else {
orb_publish(ORB_ID(transponder_report), _transponder_report_pub, &t);
}

_last_utm_global_pos_com = t.timestamp;
}

void
MavlinkReceiver::handle_message_collision(mavlink_message_t *msg)
{
Expand Down
3 changes: 3 additions & 0 deletions src/modules/mavlink/mavlink_receiver.h
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Original file line number Diff line number Diff line change
Expand Up @@ -119,6 +119,7 @@ class MavlinkReceiver : public ModuleParams

void handle_message(mavlink_message_t *msg);
void handle_message_adsb_vehicle(mavlink_message_t *msg);
void handle_message_utm_global_position(mavlink_message_t *msg);
void handle_message_att_pos_mocap(mavlink_message_t *msg);
void handle_message_battery_status(mavlink_message_t *msg);
void handle_message_collision(mavlink_message_t *msg);
Expand Down Expand Up @@ -273,6 +274,8 @@ class MavlinkReceiver : public ModuleParams

uORB::Subscription _param_update_sub{ORB_ID(parameter_update)};

hrt_abstime _last_utm_global_pos_com{0};

DEFINE_PARAMETERS(
(ParamFloat<px4::params::BAT_CRIT_THR>) _param_bat_crit_thr,
(ParamFloat<px4::params::BAT_EMERGEN_THR>) _param_bat_emergen_thr,
Expand Down