RC_CHANNELS reading with OpenVSCode

Blue Robotics Software ArduSub
1

Hey all!

For a little test, I’d like to read the RC_CHANNELS data from MavLink using a python script in the OpenVSCode extension.

I’ve installed the pymavlink using pip install, and I tried to make a script to connect to udp 127.0.0.1:14550 and udp 0.0.0.0:14550. I thought by looking at the MAVLink Endpoints in BlueOS, that the GCS Server Link would be at 0.0.0.0:14550, so that reading the RC_CHANNELS could be readed through a UDP Client 127.0.0.1:14550 Endpoint aswell.

Here is my python script:

from pymavlink import mavutil
import time

# This is the endpoint BlueOS uses by default for companion apps:
connection_string = 'udpin:0.0.0.0:14550'

print(f"Connecting to MAVLink on {connection_string} ...")
mav = mavutil.mavlink_connection(connection_string)

print("Waiting for vehicle heartbeat...")
mav.wait_heartbeat()
print("Connected! Reading RC channels (press Ctrl+C to stop)")

try:
    while True:
        msg = mav.recv_match(type='RC_CHANNELS', blocking=True, timeout=1)
        if msg:
            # Print first 8 RC channels
            print(" ".join([f"RC{i}: {getattr(msg, f'chan{i}_raw', None)}" for i in range(1,9)]))
        else:
            print("No RC_CHANNELS message received.")
        time.sleep(0.2)
except KeyboardInterrupt:
    print("\nExiting.")

Am I missing something, or maybe using the wrong command to actually connect to the UDP port?

Thanks in advance!

2

It should be possible to read messages with pymavlink, but you haven’t specified which part isn’t working as intended.

Some ideas that might be worth considering:

By the way, are you using radio communication, or are you actually wanting to check the MAVLink-based pilot inputs (e.g. with RC_CHANNELS_OVERRIDE), or the servo rail outputs (via SERVO_OUTPUT_RAW)?

3

Hey @EliotBR !

I’ve set up a new UDP Client specifically for pymavlink communication on 127.0.0.1:14575.

At this point I’m only trying to receive a heartbeat, just as a little test if I’m actually able to read any Mavlink messages with pymavlink in this setup.

This is my code to get the heartbeat:

from pymavlink import mavutil

connection_str = 'udp:0.0.0.0:14575'   # Listen on all interfaces, port 14575 (adjust port if needed)
print(f"Connecting to MAVLink at {connection_str}...")
master = mavutil.mavlink_connection(connection_str)

print("Waiting for vehicle heartbeat...")
master.wait_heartbeat()
print(f"Heartbeat received from system {master.target_system}, component {master.target_component}")

from pymavlink.dialects.v20 import common as mavlink2
AUTOPILOT_COMPONENT_ID = mavutil.mavlink.MAV_COMP_ID_AUTOPILOT1

if master.target_component != AUTOPILOT_COMPONENT_ID:
    print("Waiting specifically for autopilot heartbeat...")
    # Wait for a heartbeat from the autopilot component
    while True:
        hb = master.recv_match(type='HEARTBEAT', blocking=True, timeout=10)
        if hb and hb.get_srcComponent() == AUTOPILOT_COMPONENT_ID:
            master.target_component = AUTOPILOT_COMPONENT_ID
            print(f"Autopilot heartbeat received from system {hb.get_srcSystem()}, component {hb.get_srcComponent()}")
            break

In my final use-case, I’d like to read the joystick axis (HID Device) to automate some extra things. So I guess I need to read the RC_CHANNELS messages?