Send and receive custom message over mavlink

ArduCopter
1

Hi
i try to send custom message from mission planner to copter and receive response i but i newbe on this project can anyone help me or send me your document what function must be add and where or send my some example
thank for help

2

Follow this guide: Adding a new MAVLink Message — Dev documentation

For additional clarity (First refer to the above guide!), Example:

I defined a message definition in ardupilotmega.xml:

<message id="333" name="CUSTOMMSG">
      <description>Custom Data</description>
      <field type="char[4]" name="Packet" units="packet">Packet Number</field>
      <field type="char[251]" name="Data" units="unit">Data Values</field>
    </message>

Defining variables in …/ArduCopter/GCS_Mavlink.h:

// Test vars
const char* custom_data;
const char* packet_number;

Handling the message in the GCS_MAVLINK_Copter::handle_message(const mavlink_message_t &msg) function of …/ArduCopter/GCS_Mavlink.cpp:

case MAVLINK_MSG_ID_CUSTOMMSG:   // MAV ID: 333
        {
            // decode packet
            mavlink_custommsg_t packet;
            mavlink_msg_custommsg_decode(&msg, &packet);

            custom_data = packet.Data;
            packet_number = packet.Packet;

            mavlink_msg_custommsg_send(chan, packet_number, custom_data);
            break;
        }

Further, on the GCS side,
To send data:

from pymavlink import mavutil

connection = mavutil.mavlink_connection('udp:127.0.0.1:14550')
connection.wait_heartbeat()

packet_num = 1
msg  = "Hello! This is a Custom Message"

connection.mav.send(
            mavutil.mavlink.MAVLink_custommsg_message(
                Packet = f"{packet_num}".encode(),
                Data = msg.encode(),
            )
        )

For receiving the message:

from pymavlink import mavutil

connection = mavutil.mavlink_connection('udp:127.0.0.1:145502)
connection.wait_heartbeat()

msg = connection.recv_msg()
        if msg:
            msg = msg.to_dict()

            if msg["mavpackettype"] == "CUSTOMMSG":
                print(msg)
2 Likes
3

Thanks for your help its very helpful
But how can i send messages in the firmware without py script and receive message on firmware send by mission planner
i want to send command from mission planner to sensor and view sensor output on mission planner
its that possible?

4

ill try to send message by your example but i have this error when i try build firmware:

/home/—/.espressif/tools/xtensa-esp32-elf/esp-2021r2-patch5-8.4.0/xtensa-esp32-elf/bin/…/lib/gcc/xtensa-esp32-elf/8.4.0/…/…/…/…/xtensa-esp32-elf/bin/ld: /home/—/ardupilot/build/esp32empty/lib/bin/libarduplane.a(failsafe.cpp.50.o):/home/—/ardupilot/build/esp32empty/…/…/ArduPlane/GCS_Mavlink.h:9: multiple definition of `custom_data’; /home/—/ardupilot/build/esp32empty/lib/bin/libarduplane.a(ArduPlane.cpp.50.o):/home/—/ardupilot/build/esp32empty/…/…/ArduPlane/GCS_Mavlink.h:9: first defined here

rebuild for copter in problem solved