mavlink / c_uart_interface_example

Simple MAVLink to UART interface example for *nix systems

MAVLink

MAVLink -- Micro Air Vehicle Message Marshalling Library.

MAVLink is a very lightweight, header-only message library for communication between drones and/or ground control stations. It consists primarily of message-set specifications for different systems ("dialects") defined in XML files, and Python tools that convert these into appropriate source code for supported languages. There are additional Python scripts providing examples and utilities for working with MAVLink data.

Tip MAVLink is very well suited for applications with very limited communication bandwidth. Its reference implementation in C is highly optimized for resource-constrained systems with limited RAM and flash memory. It is field-proven and deployed in many products where it serves as interoperability interface between components of different manufacturers.

Quick start

Generate C headers

To install the minimal MAVLink environment on Ubuntu LTS 20.04 or 22.04, enter the following on a terminal:

# Dependencies
sudo apt install python3-pip

# Clone mavlink into the directory of your choice
git clone https://github.com/mavlink/mavlink.git --recursive
cd mavlink

python3 -m pip install -r pymavlink/requirements.txt

You can then build the MAVLink2 C-library for message_definitions/v1.0/common.xml from the /mavlink directory as shown:

python3 -m pymavlink.tools.mavgen --lang=C --wire-protocol=2.0 --output=generated/include/mavlink/v2.0 message_definitions/v1.0/common.xml

Use from cmake

To include the headers in cmake, install them locally, e.g. into the directory install:

cmake -Bbuild -H. -DCMAKE_INSTALL_PREFIX=install -DMAVLINK_DIALECT=common -DMAVLINK_VERSION=2.0
cmake --build build --target install

Then use find_package to get the dependency in CMakeLists.txt:

find_package(MAVLink REQUIRED)

add_executable(my_program my_program.c)

target_link_libraries(my_program PRIVATE MAVLink::mavlink)

And pass the local install directory to cmake (adapt to your directory structure):

cd ../my_program
cmake -Bbuild -H. -DCMAKE_PREFIX_PATH=../mavlink/install

For a full example, check examples/c.

Note: even though we use target_link_libraries in cmake, it doesn't actually "link" to MAVLink as it's just a header-only library.

Other instructions

Instructions for using the C libraries are then covered in Using C MAVLink Libraries (mavgen).

Note: Installing the MAVLink Toolchain explains how to install MAVLink on other Ubuntu platforms and Windows, while Generating MAVLink Libraries explains how to build MAVLink for the other programming languages supported by the project. The sub-topics of Using MAVLink Libraries explain how to use the generated libraries.

Key Links

• Documentation/Website (mavlink.io/en/)
• Discussion/Support
• Contributing
• License

c_uart_interface_example's Issues

Can`t make

Hello.

when I make mavlink/c_uart_interface_example ,error occoured.
I want to know how solve this problem.
like this ↓

ubuntu@ubuntu-CFSZ5-3:~/c_uart_interface_example$ make
git submodule update --init --recursive
Submodule 'mavlink/include/mavlink/v1.0' (git://github.com/mavlink/c_library.git) registered for path 'mavlink/include/mavlink/v1.0'
Cloning into 'mavlink/include/mavlink/v1.0'...
fatal: unable to connect to github.com:
github.com[0: 192.30.255.113]: errno=Connection timed out
github.com[1: 192.30.255.112]: errno=Connection timed out

fatal: clone of 'git://github.com/mavlink/c_library.git' into submodule path 'mavlink/include/mavlink/v1.0' failed
makefile:7: recipe for target 'git_submodule' failed
make: *** [git_submodule] Error 128

Can not fly !

Hello, I am trying to fly my quadrocopter drones. And my platform is NVIDIA Xavier-(Linux)，I use this uart-interface and the example in it ,try to let the uav fly to 2m. I had the blades removed indoors for the experiment, and the GPS signal was good，after I run mavlink_control , I can see the flight mode changed into offboard,But none of the four motors responded, and soon the safety switch was locked again. How conld I make the uav fly to 2m by sending mavlink message from linux uart?

Does example surpport Ardupilot version 4.3.4

Hi
I test this example, I use cuav x7+,the firmware is Ardupilot 4.3.4.
I build the example under ubuntu 20.04, everything goes well except run the command

./mavlink_control -d /dev/ttyACM0

it stop at

GOT AUTOPILOT COMPONENT ID: 1

I also find this reference

#16

thanks

can not simulate with jmavsim or Gazebo

Hello, new user here. I tried to simulate the example application with both Jmavsim and Gazebo by running "./mavlink_control -u 127.0.0.1 -a". I see on the QGroundControl that the drone gets armed at the start and disarmed in the end so I think the commands are sent successfully but there is no takeoff, no movement and no landing happens. What am I doing wrong?

Replace send_quad_commands example with offboard control example

@julianoes @thomasgubler Issue to track the relevant discussion here:
https://groups.google.com/forum/#!topic/px4users/IC1iz_TsL_Y

For all people interested to send high-rate set points offboard: What needs to be done is:

• Update the files in the mavlink folder with this: https://github.com/mavlink/c_library
• Replace the send_quads message with the appropriate SET_ATTITUDE_TARGET and SET_POSITION_TARGET messages: http://mavlink.org/messages/common#SET_POSITION_TARGET_LOCAL_NED
• Provide a decent README.md how to configure and operate the system to make this work

Having an example ready that works out of the box would be a huge step forward.

Delayed Sensor Data

So I am trying to run a terrain mapping algorithm using pixHawk IMU data and a line scanning LIDAR. Needless to say I am using this code to pull data from the PixHawk. I also have a way to record data from the LIDAR. A problem occurs with the synchronization of the two sensors.... My system works like this:

1) Initialize the sensors and get them streaming data but do not start recording data.
2)When all sensors are ready I start grabbing and recording the most current messages from all both sensors at once. (trying to get close to synced)
3)When the test is done I stop both sensors together and disconnect.

The time stamps I create when recording tell me that my sensors do in-fact start and stop at the same time and are running at about the same sampling rate. However when I go to create a point cloud from the data the only way to make something even half decent is to trim the start of the pixHawk data like shown below:

This was a quick test where I tried to turn the pixHawk 90 degrees every 5 seconds.... as you can see its about .75-1.25 seconds off at every turn (exception on the first turn when I jumped the gun).

Since I am still getting the correct length of time from both sensors, this makes me feel like the "current" messages being grabbed and recorded from the pixHawk are actually delayed by about a second.... I guess this would be more an internal pixHawk problem than a problem with this code itself but is anyone else getting similar or better results? Is this a normal time delay to get messages from the pixHawk? Any thoughts to fix this would be appreciated.

Thanks

Error reading messages in serial_port.cpp

I apologize if this is not the correct place to ask this but I was not sure where to ask. I am using the c_uart_interface_example as a starting point for sending and receiving mavlink for my own project. I am running SITL and then piping that output into a pseudoterminal (so /dev/pts/) and then opening that as a serial port so I can test the interface without the actual hardware. Using mavproxy works fine for receiving data over the pseudoterminal but I am having trouble with the example serial port interface in this code. I get a lot of the messages, but it seems like I am dropping a good amount of them as well. I am not sure why this would be as I was under the impression that pseudoterminals were handled like other serial ports. I tried playing around with everything I could think of and nothing seems to make a difference. Attached is a snippet of the output with debug mode turned on. Thanks for your help!

Couldn't find <common/mavlink.h> file

hi,
When I run "make" to build this project, it shows the library included in mavlink_control.h <common/mavlink.h> couldn't be found. Any ideas?

Failed to run the command: nsh> mavlink -d /dev/ttyACM0

Hi. I want to learn about the communication mechanism between pixhawk and ubuntu PC(especially with ROS), but I failed to run the command mentioned in the title. Could you please give me some instructions?
It reported that "bash: mavlink: Is a directory."
Thanks.

Dropped packet issue

For some reason, after compiling the program and executing the program, no response is received after finding a response and discovering the system ID and component ID.

I changed debug to true and found that there is a dropped packet. I've been looking through the msg IDs that are posted to the command console, it seems that all msg IDs are handled at some point. A few msgs by some random basis seem to be dropped completely.

Is this a bug that hasn't been resolved yet?

How to add new message?

Good day! I add new message in https://github.com/mavlink/mavlink use ./mavgenerate.py (for 1.0) and replace common on generated common. After that, I got a lot of errors. How should I create a new message?

g++ -I mavlink/include/mavlink/v1.0 mavlink_control.cpp serial_port.cpp autopilot_interface.cpp -o mavlink_control -lpthread In file included from mavlink/include/mavlink/v1.0/common/common.h:1269:0, from mavlink/include/mavlink/v1.0/common/mavlink.h:32, from mavlink_control.h:70, from mavlink_control.cpp:56: mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h:7:38: error: types may not be defined in parameter types typedef struct __mavlink_heartbeat_t { ^ In file included from mavlink/include/mavlink/v1.0/common/common.h:1269:0, from mavlink/include/mavlink/v1.0/common/mavlink.h:32, from mavlink_control.h:70, from mavlink_control.cpp:56: mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h:14:1: error: typedef declaration invalid in parameter declaration }) mavlink_heartbeat_t; ^ mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h:14:4: error: expected constructor, destructor, or type conversion before ‘mavlink_heartbeat_t’ }) mavlink_heartbeat_t; ^ mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h: In function ‘uint16_t mavlink_msg_heartbeat_pack(uint8_t, uint8_t, mavlink_message_t*, uint8_t, uint8_t, uint8_t, uint32_t, uint8_t)’: mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h:80:5: error: ‘mavlink_heartbeat_t’ was not declared in this scope mavlink_heartbeat_t packet; ^ mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h:81:5: error: ‘packet’ was not declared in this scope packet.custom_mode = custom_mode; ^ mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h:92:159: error: too many arguments to function ‘uint16_t mavlink_finalize_message(mavlink_message_t*, uint8_t, uint8_t, uint8_t, uint8_t)’ return mavlink_finalize_message(msg, system_id, component_id, MAVLINK_MSG_ID_HEARTBEAT_MIN_LEN, MAVLINK_MSG_ID_HEARTBEAT_LEN, MAVLINK_MSG_ID_HEARTBEAT_CRC); ^ In file included from mavlink/include/mavlink/v1.0/common/../protocol.h:79:0, from mavlink/include/mavlink/v1.0/common/common.h:30, from mavlink/include/mavlink/v1.0/common/mavlink.h:32, from mavlink_control.h:70, from mavlink_control.cpp:56: mavlink/include/mavlink/v1.0/common/../mavlink_helpers.h:99:25: note: declared here MAVLINK_HELPER uint16_t mavlink_finalize_message(mavlink_message_t* msg, uint8_t system_id, uint8_t component_id, ^ In file included from mavlink/include/mavlink/v1.0/common/common.h:1269:0, from mavlink/include/mavlink/v1.0/common/mavlink.h:32, from mavlink_control.h:70, from mavlink_control.cpp:56: mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h: In function ‘uint16_t mavlink_msg_heartbeat_pack_chan(uint8_t, uint8_t, uint8_t, mavlink_message_t*, uint8_t, uint8_t, uint8_t, uint32_t, uint8_t)’: mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h:123:5: error: ‘mavlink_heartbeat_t’ was not declared in this scope mavlink_heartbeat_t packet; ^ mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h:124:5: error: ‘packet’ was not declared in this scope packet.custom_mode = custom_mode; ^ mavlink/include/mavlink/v1.0/common/./mavlink_msg_heartbeat.h:135:170: error: too many arguments to function ‘uint16_t mavlink_finalize_message_chan(mavlink_message_t*, uint8_t, uint8_t, uint8_t, uint8_t, uint8_t)’ return mavlink_finalize_message_chan(msg, system_id, component_id, chan, MAVLINK_MSG_ID_HEARTBEAT_MIN_LEN, MAVLINK_MSG_ID_HEARTBEAT_LEN, MAVLINK_MSG_ID_HEARTBEAT_CRC); ^

Cannot build on Fedora Silverblue/uBlue OS

I downloaded your repository and extracted it, entered the folder, ran git init and then make:

 make
git submodule update --init --recursive
g++ -g -Wall -I mavlink/include/mavlink/v2.0 mavlink_control.cpp serial_port.cpp udp_port.cpp autopilot_interface.cpp -o mavlink_control -lpthread
In file included from mavlink_control.cpp:56:
mavlink_control.h:70:10: fatal error: common/mavlink.h: No such file or directory
   70 | #include <common/mavlink.h>
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
In file included from serial_port.cpp:55:
serial_port.h:65:10: fatal error: common/mavlink.h: No such file or directory
   65 | #include <common/mavlink.h>
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
In file included from udp_port.cpp:57:
udp_port.h:76:10: fatal error: common/mavlink.h: No such file or directory
   76 | #include <common/mavlink.h>
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
In file included from autopilot_interface.h:58,
                 from autopilot_interface.cpp:55:
generic_port.h:59:10: fatal error: common/mavlink.h: No such file or directory
   59 | #include <common/mavlink.h>
      |          ^~~~~~~~~~~~~~~~~~
compilation terminated.
make: *** [makefile:4: mavlink_control] Error 1
asterix@fedora:~/groundController/c_uart_interface_example$ 

Looks like something is missing?

It stopped at "CHECK FOR MESSAGES"

.Using a UART (serial) connection
.TELEM2
.The USB-to-serial adapter board is not a FTDI chip, but a CH340G chip of China.
.Then using a USB connection, it also stopped at here.

throttle cut when sending only position command outdoors

Hi Everyone,

I've run a few more tests and flights and am still finding that my motors want to cut out whenever i send only a position command. I'm now using the offboard mode switch, which is very nice btw, but hasn't changed this behavior.

Has anyone run this new version of c_uart_interface_example outdoors on a gps system?

Many thanks,

• Trent

Able to write, unable to get actions.

Our code is like this code, but more simplified. We are able to read, and write (at least it's not giving us errors when trying to write to the pixhawk). But we are not able to control anything. We tried using px4 and ardupilot, but we still get nothing working with writing.

Is there any like any handshake to establish communication to the pixhawk?

What to packets to send to make motors spin or to make a sound on the buzzer?

get mission list with c_uart_interface_example

Hi, I am using this c_uart_interface_example to communicate with pixhawk(which is APM stack controller). I've done change the flight mode and RCOverride in Loiter mode and so on. Right now, I want to receive the mission items in AUTO mode, I use some API incommon based on mission tittles. But it seems not work. It supposed have a mission-list kind of API to receive entire list including all the mission items. Could you give me some suggestions? If I am not clear, please correct me.
Thanks so much.

lin

current_setpoint should be guarded with a mutex

I have been going through this code and thought I would point out that current_setpoint is written from the main thread and read from the writing thread without any protection (i.e., a mutex or a lock). Although unlikely, it possible that current_setpoint is read by the writing thread while being written from the main thread which could result in things going to hell very quickly since we are talking about a quadcopter or similar here.

In contrast to this, I am almost certain that reading and writing to the serial port from different threads just works in POSIX and doesn't need any mutexes.

Some commands not working

I am utilizing an off-board computer to control the Pixhawk using v3.3.3 firmware
The MAVLink documentation states that REQUEST_DATA_STREAM is deprecated and to instead use SET_MESSAGE_INTERVAL.
However when I try to utilize the command_long encode to send I get no response as per the following c++ code:

**mavlink_command_long_t com = { 0 };
com.target_system = system_id;
com.target_component = autopilot_id;
com.command = MAV_CMD_GET_MESSAGE_INTERVAL;
com.confirmation = 0;
com.param1 = mav_msg_ID; //The MAVLink message ID
com.param2 = interval_us; //The interval between two messages, in microseconds. Set to -1 to disable and 0 to request default rate.
printf("Sent request for ID#:%.0f to be output every %.0f us\n",com.param1, com.param2);

mavlink_message_t message;
mavlink_msg_command_long_encode(system_id, companion_id, &message, &com); //Encode

int len = serial_port->write_message(message); //Send the message
return len;**

this is based off the toggle_offboard utilized in c_uart_example code also under mavlink.

I assume this is due to the library being version 1. I tried to add the mavlink_msg_message_interval.h file to the common folder in library 1 however I get no response from the pixhawk. We have tried basemode as 3 and 12. neither likes it
The code used for this was based off ned utilizing the encode from inside the particular .h file

Any help would be appriciated as only the deprecated method of requesting data from the pixhawk seems to work.

It stopped at he lline "GOT AUTOPILOT COMPONENT ID: 1".

hello
I make the c_uart_interface_example and use the command ./mavlink_control -d /dev/ttyACM0.
but the programme cannot go on. It stopped at he lline "GOT AUTOPILOT COMPONENT ID: 1".
Please help me.
Thank you.
what have I done as follows:

---

ghf@ghf-A8SR:$ cd c_uart_interface_example/
ghf@ghf-A8SR:/c_uart_interface_example$ ./mavlink_control -d /dev/ttyACM0
OPEN PORT
Connected to /dev/ttyACM0 with 57600 baud, 8 data bits, no parity, 1 stop bit (8N1)

START READ THREAD

CHECK FOR MESSAGES
Found

GOT VEHICLE SYSTEM ID: 1
GOT AUTOPILOT COMPONENT ID: 1

Can't pass GOT VEHICLE SYSTEM ID: 1 GOT AUTOPILOT COMPONENT ID: 1

Hello,

I was trying to use c_uart, but it fails to pass autopilot component id:1. I check this issue #14 but its solution doesn't help me because I can't do step 3 and this step: "Now screen into pixhawk and press Enter, you will see nsh prompt. Start the mavlink application on Telem 2 port which is /dev/ttyS2"
I can't log into nsh prompt.
http://imgur.com/a/BJqsb

I plugged my px4 via USB.
Sorry for my english, I don't speak english too much.
Regards

Switch custom mode and base mode

Hi everyone

I'm working on offboard control of multicopter using c_uart_interface, pixhawk and mavlink.
It might seem useless to know how to switch custom and base mode's autopilot for me but I'm curious and I don't understand the way to do it.

I saw https://dev.px4.io/en/concept/flight_modes.html , px4_custom_mode.h, MAV_MODE, MAV_MODE_FLAG, commander_state.msg in firmware but it muddled up to me the spirit !

What the difference between custom mode, base mode, main mode, main state and how use it with mavlink ?

Thanks you in advance,
Thomas

How to send position feedback from motion capture system?

Hi,

I am interested to send some high-level control commands to pixhawk using MAVLink, indoors. So, I have a motion capture system setup which gives accurate XYZ and orientation. I would like to tell pixhawk this information in order to use it onboard instead of e.g. GPS. How can I do that?

Thanks.

Obstacle avoidance?

Hello,

As part of a Senior project I am attempting to implement obstacle avoidance on a DJI F450 quadcopter using the pixhawk, PX4, and 4 HC-SR04 ultrasonic sensor units. My idea to accomplish this is, a raspberry pi would interface the 4 sonar sensors and when a sensor had been triggered the pi would relay mavlink messages to the pixhawk to instruct it to navigate away from the object, and then give control back to the Manual RC input or Qgroundcontrol. I initially intended to utilize MAVproxy to allow the pi to send mavlink messages, however after seeing this repository, I felt it was more suited to the task. In my inital testing I am currently running a C program on the pi that gathers sonar data and executes, system("./mavlink_control -d /dev/ttyAMC0"), which executes a set position mavlink command.

As you can probably tell I am very new to this and was hoping a more experienced developer could answer a few of my questions that I can't seem to find the answer for:

1.)
are the axis directions in:
set_position(float x, float y, float z, mavlink_set_position_target_local_ned_t &sp)
in reference to the quads orientation as in, setting x = x+1.0 will cause the quad to move 1 meter forward or will it cause the quad to move 1 meter true north?

2.)
would I be better served to simply set the pitch/roll for a short period of time in the appropriate direction?

3.)
does this sound like a reasonable design for a rudimentary avoidance system?

Thanks so much for any help!

Brad

Not working

Tried with Pixhawk 2.4.8 and the latest ardupilot firmware, no messages are retrieved, the implementation is supposedly broken as the Mission planner can correctly get messages.

Timestamps reference

In ardupilot_interface.cpp the timestamps of MavLink messages can be obtained with "current_messages.time_stamps".
Which is the reference of these timestamps?
Are they directly referred to GPS timestamp or they are referred to the internal clock of the autopilot? I refer to outdoor conditions with optimal GPS signal.