Matlab to Mission Planner SITL (MavLink connection)

Hi,

I am opening the SITL Simulation in Mission Planner (Simulation Tab -> Mulitrotor).

My aim is to setup a Bidirectional Mavlink2 communication between Matlab and Mission Planner simulation. I want to be able to send commands from Matlab to MP and se the behaviour of the dron.

I am able to receive forwarded messages from Mission Planer. I set up Ctrl + F, then open Connection to 14552 UDP Port.

However if I want to send something Back, Mission Planner dose not see it. In Mavlink Inspector I can see only

Vechicle 1

- Comp 1 MAV_COMP_ID_AUTOPILOT1

Mechicle 255

- Comp 190 MAV_COMP_ID_MISSIONPLANNER

The code below I use to try to send a HEARTBEAT messages to Mission Planner.

% === CONNECTION CONFIGURATION ===
localPort = 14552;       % Local UDP port (match SITL config)
targetSys = 1;
targetComp = 1;
% === Initialize MAVLinkIO ===
dialect = mavlinkdialect("common.xml", 2);
mav = mavlinkio(dialect);
connect(mav, "UDP", "LocalPort", localPort);
% === Create drone target client ===
client = mavlinkclient(mav, targetSys, targetComp);
% === Register MATLAB as GCS client (sysid 255, compid 1) ===
gcs = mavlinkclient(mav, 255, 1);
% === Subscriptions for responses ===
ackSub = mavlinksub(mav, client, "COMMAND_ACK");
statustextSub = mavlinksub(mav, client, "STATUSTEXT");
% === Send HEARTBEATs periodically ===
disp("📡 Sending HEARTBEAT every 1 second...");
heartbeat = createmsg(dialect, "HEARTBEAT");
heartbeat.Payload.autopilot = 8;  % MAV_AUTOPILOT_INVALID
heartbeat.Payload.base_mode = 0;
heartbeat.Payload.custom_mode = uint32(0);
heartbeat.Payload.system_status = 0;
heartbeat.Payload.type = 6;       % MAV_TYPE_GCS (Ground Station)
duration = 30;  % seconds
startTime = tic;

while toc(startTime) < duration
    sendmsg(mav, heartbeat);
    fprintf("❤️ Sent HEARTBEAT at t=%.1f sec\n", toc(startTime));
    pause(1.0);
end

% === Check COMMAND_ACKs ===
ackMsgs = latestmsgs(ackSub, 1);
for i = 1:numel(ackMsgs)
    fprintf("✅ COMMAND_ACK: cmd=%d, result=%d\n", ...
        ackMsgs(i).Payload.Command, ackMsgs(i).Payload.Result);
end

% === Check STATUS_TEXTs ===
statusMsgs = latestmsgs(statustextSub, 1);
for i = 1:numel(statusMsgs)
    txt = native2unicode(char(statusMsgs(i).Payload.Text'), 'UTF-8');
    txt = erase(txt, char(0));
    fprintf("📥 STATUS: [%d] %s\n", ...
        statusMsgs(i).Payload.Severity, strtrim(txt));
end

% === Cleanup ===
disconnect(mav);
delete(mav);
disp("✅ Done");

I do not know how to solve it. Maybe I have to switch something in Mission Planner, but it is not clear to me what. Is it possible to set a connection I would like to have. All help will be appreciated.

Answer 1

[Jianxin Sun]

Hi, if you are already able to receive message at 14552, you can try the following script. I updated the heartbeat message to preserve message field data type. Previously the fields were overwritten to double type.

I also used parameter protocol to test sending parameter request.

% === CONNECTION CONFIGURATION ===
localPort = 14552;       % Local UDP port (match SITL config)
targetSys = 1;
targetComp = 1;
% === Initialize MAVLinkIO ===
dialect = mavlinkdialect("common.xml", 2);
mav = mavlinkio(dialect);
connect(mav, "UDP", "LocalPort", localPort);
% === Create drone target client ===
client = mavlinkclient(mav, targetSys, targetComp);
% === Register MATLAB as GCS client (sysid 255, compid 1) ===
gcs = mavlinkclient(mav, 255, 1);
% === Send HEARTBEATs periodically ===
% It is important to preserve the struct field type using (:)= assignment
disp("📡 Sending HEARTBEAT every 1 second...");
heartbeat = createmsg(dialect, "HEARTBEAT");
heartbeat.Payload.autopilot(:) = 8;  % MAV_AUTOPILOT_INVALID
heartbeat.Payload.base_mode(:) = 0;
heartbeat.Payload.custom_mode(:) = uint32(0);
heartbeat.Payload.system_status(:) = 0;
heartbeat.Payload.type(:) = 6;       % MAV_TYPE_GCS (Ground Station)
duration = 30;  % seconds
startTime = tic;

while toc(startTime) < duration
    sendmsg(mav, heartbeat);
    fprintf("Sent HEARTBEAT at t=%.1f sec\n", toc(startTime));
    pause(1.0);
end

% === Use parameter request to get parameter values ===
sub = mavlinksub(mav, client, "PARAM_VALUE", NewMessageFcn=@(~,msg)disp(msg.Payload), BufferSize=30);
msg = createmsg(dialect,"PARAM_REQUEST_LIST");
msg.Payload.target_system(:) = targetSys;
msg.Payload.target_component(:) = targetComp;
sendmsg(mav,msg,client)
pause(1)

% === Cleanup ===
disconnect(mav);
delete(mav);
disp("✅ Done");