Release Notes

ATOM UAV MANUAL

Date:

2022

Version: 1.3

Page: 22 of 39

FLARM Technology

Ltd

Hinterbergstrasse 15

CH-6330 Cham

Document Number:

FTD-088

With “MAV_1_FORWARD: 1”, Atom UAVs Heartbeat will be forwarded to the

Ground Control Station and can be seen in its MAVLink Inspector with the

component id 160.

The status of the MAVLink connection is shown on the Atom UAV web interface in

the “MAVLink” page.

5.1.2 External Navigation Source

Instead of using the integrated GNSS module for positioning, Atom UAV can use

the navigation solution from a flight controller such as a PX4. This can be selected

through configuration.

Note: The FLARM radio protocol relies on accurate (milliseconds) timing.

Inaccurate timing will gradually lead to a loss of connectivity with other

FLARM systems. Configurations using the external navigation source must

be thoroughly validated against a stock Atom UAV, or any other reference

unit.

5.1.2.1 Setup

When MAVLink is selected as a GNSS source (see Section 4.1.5), Atom UAV

consumes the GPS_RAW_INT and SYSTEM_TIME messages and issues the

TIMESYNC message for time synchronization. Because the FLARM RF protocol is

time-sensitive, the provided MAVLink time base needs to be accurate. To reduce

jitter, a MAVLink mode such as OSD should be used that emits SYSTEM_TIME and

GPS_RAW_INT, but as few as possible other messages. It is crucial that the system

time of the flight controller system is sufficiently accurate and aligned with the GPS

time. If the time drifts more than ~10 ms, the receive/transmit timing of the

FLARM system might go into a state where it is not visible to other vehicles and

does not receive traffic information from surrounding aircraft.

5.1.2.2 Timepulse offset

A static time offset is configurable to compensate for systematic latency. To

configure the timepulse offset, a GNSS antenna must be connected to the Atom

UAV and a position fix must be acquired on both Atom UAV and PX4. When a

position and time fix is available from both Atom UAV and PX4, the Atom UAV

automatically and continuously measures the time offset. This shown and

continuously updated in the web interface in the “MAVLink” page (see Section

4.1.5).

Once a consistent time pulse offset is observed, this must be set in the MAVLink

configuration page.