Raspberry Pi 4B Pixhawk 6X autonomous control

PX4 Autopilot
1

Hi,

I built the drone in this post I still have to do the PID tuning, waiting for better weather, in the meantime I want to get communication between my Pi and Pixhawk working.

I am currently trying to get sensor data in a C++/Python script and command the drone to fly autonomously.

This is my setup:

  • Raspberry Pi 4B running Ubuntu 22.04 (ROS 2 Humble)

  • Pixhawk 6x

  • UART connection from RPi to Telem 2 on Pixhawk

I followed this to setup the Pi:

image

Parameters set:
image
image

Following this post here and here

Only response I get working:

Run:
sudo mavproxy.py --master=/dev/serial0 --baudrate 57600
Output:

osprey@osprey:~$ sudo mavproxy.py --master=/dev/serial0 --baudrate 57600
                  Connect /dev/serial0 source_system=255
                  Log Directory: 
                  Telemetry log: mav.tlog
                  Waiting for heartbeat from /dev/serial0
                  MAV> Detected vehicle 1:1 on link 0
                  online system 1
                  MANUAL> Mode MANUAL
                  fence breach
                  Received 932 parameters
                  Saved 932 parameters to mav.parm

I tried python mavsdk here:

When running the code below I get the result in the second box where it does not pickup the pixhawk.

image
image810×192 27 KB

I tried this all parms file and it just hangs with no response.

Lastly I also tried ROS example to read sensor data here and I’m getting compile error when I do colcon build.

I would appreciate guidance as I’m new to PX4/MavLink/SDK

My goal is to control the quad with the raspberry pi. What is the best way to do this and the steps to follow to get the necessary packages setup.

Best,
Marno

2

Ok, so the issue is that mavsdk_server tries to connect to udp://:14540. That address is usually only available in SITL.

If you have it connected via serial, you want to start it like this:

~/.local/lib/python3.9/site-packages-mavsdk/bin/mavsdk_server serial:///dev/serial0:57600
1 Like
3

Thank you for the reply.

When I run your cli line:

~/.local/lib/python3.10/site-packages-mavsdk/bin/mavsdk_server serial:///dev/serial0:57600

I get:

-bash: /home/osprey/.local/lib/python3.10/site-packages-mavsdk/bin/mavsdk_server: No such file or directory

When I cange it to where my mavsdk_server is:

~/.local/lib/python3.10/site-packages/mavsdk/bin/mavsdk_server serial:///dev/serial0:57600

I get:

[09:48:06|Info ] MAVSDK version: v1.4.16 (mavsdk_impl.cpp:20)
[09:48:06|Info ] Waiting to discover system on serial:///dev/serial0:57600... (connection_initiator.h:20)
[09:48:06|Error] open failed: Permission denied (serial_connection.cpp:88)
[09:48:06|Error] Connection failed: Connection error (connection_initiator.h:47)

Connections:

IMG-8321
IMG-83211920×2560 362 KB

4

Okay so one step closer!

Code

Terminal 1 (Start the MavSDK_server)

sudo ~/.local/lib/python3.10/site-packages/mavsdk/bin/mavsdk_server serial:///dev/serial0:57600

Output:

[10:21:33|Info ] MAVSDK version: v1.4.16 (mavsdk_impl.cpp:20)
[10:21:33|Info ] Waiting to discover system on serial:///dev/serial0:57600... (connection_initiator.h:20)
[10:21:33|Debug] New: System ID: 1 Comp ID: 1 (mavsdk_impl.cpp:496)
[10:21:33|Debug] Component Autopilot (1) added. (system_impl.cpp:377)
[10:21:33|Warn ] Vehicle type changed (new type: 2, old type: 0) (system_impl.cpp:225)
[10:21:33|Debug] Discovered 1 component(s) (system_impl.cpp:578)
[10:21:33|Info ] System discovered (connection_initiator.h:63)
[10:21:33|Info ] Server started (grpc_server.cpp:53)
[10:21:33|Info ] Server set to listen on 0.0.0.0:50051 (grpc_server.cpp:54)

Thoughts: Because I am running Ubuntu I have to run the code with sudo to access hardware pins.

Terminal 2 (Talk to the server with python)

Python code:

#!/usr/bin/env python3
# https://github.com/mavlink/MAVSDK-Python/blob/6955725b83314366e5448c6b12cde65f09791969/examples/all_params.py

import asyncio
from mavsdk import System


async def run():
    # Connect to the drone
    drone = System()
    print(f"drone = {drone}")
    await drone.connect(system_address="serial:///dev/serial0:57600")


    print("Waiting for drone to connect...")
    async for state in drone.core.connection_state():
        if state.is_connected:
            print(f"-- Connected to drone!")
            break

    # Get the list of parameters
    all_params = await drone.param.get_all_params()

    # Iterate through all int parameters
    for param in all_params.int_params:
        print(f"{param.name}: {param.value}")

    for param in all_params.float_params:
        print(f"{param.name}: {param.value}")

# Run the asyncio loop
asyncio.run(run())

I now get a successful connection to the drone and receive all the parameters!

1 Like
5

Glad you got it working!

See: