MAVLink Serial sniffer

MAVLink
1

Long shot, but does anyone have a Python (ideally, but C would work) script that listens for mavlink messages over a serial port and logs them with a timestamp? No need to send anything, just need to listen and log.

2

You could run a simple mavsdk example (C++) and set export MAVSDK_MESSAGE_DEBUGGING=1 to see all messages coming in and going out.

This would be an example:

#include <cstdint>
#include <future>
#include <mavsdk/mavsdk.h>
#include <iostream>
#include <thread>

using namespace mavsdk;
using namespace std::this_thread;
using namespace std::chrono;

void usage(const std::string& bin_name)
{
    std::cerr << "Usage : " << bin_name << " <connection_url>\n"
              << "Connection URL format should be :\n"
              << " For TCP : tcp://[server_host][:server_port]\n"
              << " For UDP : udp://[bind_host][:bind_port]\n"
              << " For Serial : serial:///path/to/serial/dev[:baudrate]\n"
              << "For example, to connect to the simulator use URL: udp://:14540\n";
}

std::shared_ptr<System> get_system(Mavsdk& mavsdk)
{
    std::cout << "Waiting to discover system...\n";
    auto prom = std::promise<std::shared_ptr<System>>{};
    auto fut = prom.get_future();

    // We wait for new systems to be discovered, once we find one that has an
    // autopilot, we decide to use it.
    mavsdk.subscribe_on_new_system([&mavsdk, &prom]() {
        auto system = mavsdk.systems().back();

        if (system->has_autopilot()) {
            std::cout << "Discovered autopilot\n";

            // Unsubscribe again as we only want to find one system.
            mavsdk.subscribe_on_new_system(nullptr);
            prom.set_value(system);
        }
    });

    // We usually receive heartbeats at 1Hz, therefore we should find a
    // system after around 3 seconds max, surely.
    if (fut.wait_for(seconds(3)) == std::future_status::timeout) {
        std::cerr << "No autopilot found.\n";
        return {};
    }

    // Get discovered system now.
    return fut.get();
}

int main(int argc, char** argv)
{
    if (argc != 2) {
        usage(argv[0]);
        return 1;
    }

    Mavsdk mavsdk;
    ConnectionResult connection_result = mavsdk.add_any_connection(argv[1]);

    if (connection_result != ConnectionResult::Success) {
        std::cerr << "Connection failed: " << connection_result << '\n';
        return 1;
    }

    auto system = get_system(mavsdk);
    if (!system) {
        return 1;
    }

    while (true) {
        std::this_thread::sleep_for(std::chrono::seconds(1));
    }

    return 0;
}

The CMakeLists.txt would be:


cmake_minimum_required(VERSION 3.10.2)

set(CMAKE_CXX_STANDARD 17)
set(CMAKE_CXX_STANDARD_REQUIRED ON)

project(sniffer)

add_executable(sniffer
    sniffer.cpp
)

find_package(MAVSDK REQUIRED)

target_link_libraries(sniffer
    MAVSDK::mavsdk
)

if(NOT MSVC)
    add_compile_options(sniffer PRIVATE -Wall -Wextra)
else()
    add_compile_options(sniffer PRIVATE -WX -W2)
endif()

Edit, sorry, I realize this is based on MAVSDK v2 which is not released yet. I changed it for v1 now.

3

FYI: Iā€™ve added an example to MAVSDK with that, however, that one is against v2 which has the additional intercept_ method.
The same method is available for v1, however, itā€™s part of the MavlinkPassthrough plugin there.

4

This is great!!

BTW: Is there any interest in providing -lite version of MAV SDK that does not depend on libCURL and friends (Iā€™m aware that some features would not work)? Iā€™m trying to build this quick and dirty on Win based machine and dependency management is a pain.

5

I have heard of this request before, and I get it, dependencies are a pain. Iā€™ll keep it in mind.

6

Itā€™s coming: Add option to build without cURL by julianoes Ā· Pull Request #1955 Ā· mavlink/MAVSDK Ā· GitHub

Itā€™ll only be in v2 though.

7

Cool! Iā€™ll give it a got tomorrow morning!