VOXL ESC FPV queries

Jetson Nano

@Alex-Kushleyev I am using flight core v2 as external FC. Due to which i am getting error message when i run the command px4-listener. Screenshot from 2025-01-11 12-48-02.png

Can you help me out here. how to get the data when we use external FC.

tom

@Jetson-Nano Try out voxl-inspect-mavlink, if you hit tab a couple times it should populate with the various pipes you can read from

Jetson Nano

thanks @tom for reverting back. I had already tried it and I was not able to see any RC channel data. listener function was not working.
The issue is I am not able to see the RC channel changes. Can you help me out how am I supposed to get the RC changes.

Alex Kushleyev

Hi @Jetson-Nano, sorry i originally did not realize that you are running PX4 outside VOXL2. In this case px4-listener approach will not work.

However, in the case of PX4 running on flight core (v1 or v2), there is still communication between Flight Core and VOXL2. voxl-mavlink-server should be communicating with the Flight Core via UART and passing messages back and forth. Depending whether the forwarding of RC topic is enabled or not, voxl-mavlink-server would receive those messages (if enabled) and in that case they would be accessible on VOXL2.

@tom , can you please elaborate on how to double check if the RC message is set up to forward to voxl-mavlink-server from Flight Core (if not, how to enable it) and how to actually read that message?

Thanks!

Alex

tom

@Alex-Kushleyev @Jetson-Nano You'll want to make sure that in /etc/modalai/voxl-mavlink-server.conf that en_external_uart_ap is set to true

Once you restart the service you should be able to run voxl-inspect-mavlink mavlink_offboard to view the generated messages from FC

Jetson Nano

@tom @Alex-Kushleyev thanks guys. I will check it and get back to you with the result.

Jetson Nano

@Alex-Kushleyev @tom
Guys I checked what you guys mentioned.
Screenshot from 2025-01-14 09-47-51.png
The en_external_uart_ap is set to True, but when I run the command voxl-inspect-mavlink mavlink_offboard , the terminal is showing waiting for pipe to connect and not showing anything else.

Adding to the previous point there is no mavlink_offboard showing up.

Screenshot from 2025-01-14 09-58-47.png

Alex Kushleyev

@Jetson-Nano , is voxl-mavlink-server actually running? you can check using voxl-inspect-services.

Also, are you sure that your Flight Core V2 is connected to /dev/ttyHS1 , which would be implied by using autopilot_uart_bus: 1 . How exactly are you connecting it to VOXL2?

Alex

Jetson Nano

@Alex-Kushleyev
yes the voxl-mavlink-server is running, I had checked it.

I am following this documentation for FC connections.

[link](https://docs.modalai.com/flight-core-connections/#:~:text=Using the MCBL-00010](%2F,which can lead to issues.)

Alex Kushleyev

@Jetson-Nano , can you please clarify which connector on VOXL2 is your Flight Core connected to (for uart communication) and whether you have any indication that the communication is established? Have you previously been able to connect to VOXL2 from QGC and access the Flight Core V2 while it has been connected to VOXL2?

Alex

Jetson Nano

@Alex-Kushleyev I currently use, VOXL2 USB 3.0 Expansion Adapter connected to VOXL2. From the UART7 port of the Expansion Adapter I have connected to 6-PIN Telemetry1 Port in Flight Core V2.

My connection is similar to this,

As you mentioned earlier, I'm establishing connection through port /dev/ttyHS1. When I run the cat command to read the messages from this port, I get garbled data as below,

.

I'm not exactly clear when you mean if I have tried connecting to VOXL2 from QGC and access the Flight Core V2. Few things I have tried is,

Connecting to FlightCore V2 by connecting to Wifi of VOXL2. I also have a Wifi setup on VOXL2, which also acts as my Telemetry line. From QGC I connect to this local network to access FC data and PX4 parameters on Flight Core V2.
I have tried and tested few mavlink message commads which communicate with PX4 directly for C2C.

Jetson Nano

@tom As per your response on shifting to voxl-inspect-mavlink mavlink_offboard, I see that even in mavlink server documentation from ModalAI that service pipeline is not listed. Is it that something that has to be explicitly be enabled somewhere?
Even as per the documentation, I dont see this service pipeline listed.

tom

@Jetson-Nano I could have the naming wrong. If you inspect mavlink_onboard what kind of data do you see?

Jetson Nano

@tom This is the output I get,

Screenshot from 2025-01-16 20-49-20.png

tom

@Jetson-Nano Since you don't have voxl-px4 running I think that data is likely coming from your external flight controller

Jetson Nano

@tom yes, the message is coming from external flight controller, Flight core v2. Now can you share how to double check if the RC message is set up to forward to voxl-mavlink-server from Flight Core (if not, how to enable it) and how to actually read that message?

Eric Katzfey

@Jetson-Nano Probably should also look at the pipe for messages from the flight controller to the GCS (Labeled mavlink_to_gcs in the above diagram but you'll have to double check that name). Generally the flight controller is configured with two mavlink streams. One is the onboard stream that has high rate messages and is intended for local use (e.g. on VOXL or VOXL 2) and the other is more the default settings for communication with a GCS. You can configure what each of these streams contain in PX4. You can add streams, change stream rates, etc. all via PX4 configuration. Please refer to the PX4 documentation for details on how to do this.

Jetson Nano

Hi @Eric-Katzfey, I was thinking another approach, where we can use pymavlink to get the RC_channel data. Any inputs to the mentioned approach, is it feasible?

Eric Katzfey

@Jetson-Nano Yes, that should work. You should be able to send heartbeats from a Python script using pymavlink and connect to the flight controller via voxl-mavlink-server. Then you should start receiving all the normal messages sent out by the flight controller to the GCS which should include the RC channels message.

Jetson Nano

Thank you @Eric-Katzfey ,for the confirmation with respect to the approach. Can you help me the code, maybe with providing a sample code.

I wrote a code to receive the data but the code was not connecting the Flight controller. I am providing the code here, Can you verify the code.

from pymavlink import mavutil
import time
import logging

logging.basicConfig(level=logging.INFO)

# Connection string for voxl-mavlink-server
connection_string = 'udp:192.168.8.1:14558'

# Function to send a heartbeat message
def send_heartbeat(mavlink_connection):
    mavlink_connection.mav.heartbeat_send(
        mavutil.mavlink.MAV_TYPE_GCS,         # Type: Ground Control Station
        mavutil.mavlink.MAV_AUTOPILOT_INVALID,  # Autopilot: Not a specific autopilot
        0,                                   # Base mode
        0,                                   # Custom mode
        mavutil.mavlink.MAV_STATE_ACTIVE     # State: Active
    )
    logging.info("Heartbeat sent.")

def main():
    try:
        logging.info(f"Connecting to {connection_string}...")
        # Establish MAVLink connection
        mav = mavutil.mavlink_connection(connection_string)

        # Send an initial heartbeat to register as a GCS
        logging.info("Sending initial heartbeat...")
        send_heartbeat(mav)

        # Wait for heartbeat from the flight controller
        logging.info("Waiting for heartbeat from the flight controller...")
        mav.wait_heartbeat(timeout=10)
        logging.info(f"Heartbeat received! System_ID: {mav.target_system}, Component_ID: {mav.target_component}")

        # Request RC_CHANNELS data stream at 1 Hz
        mav.mav.request_data_stream_send(
            mav.target_system,
            mav.target_component,
            mavutil.mavlink.MAV_DATA_STREAM_RC_CHANNELS,
            1,  # Stream rate in Hz (1 Hz)
            1   # Enable the stream
        )

        # Periodically send heartbeats to keep the connection alive
        last_heartbeat_time = time.time()

        while True:
            # Send a heartbeat every 1 second
            current_time = time.time()
            if current_time - last_heartbeat_time > 1:
                send_heartbeat(mav)
                last_heartbeat_time = current_time

            # Listen for incoming messages
            msg = mav.recv_match(blocking=True)
            if msg:
                msg_type = msg.get_type()
                logging.info(f"Received message: {msg_type}")

                # If it's an RC_CHANNELS message, print the values
                if msg_type == 'RC_CHANNELS':
                    logging.info(f"Channel 1: {msg.chan1_raw}")
                    logging.info(f"Channel 2: {msg.chan2_raw}")
                    logging.info(f"Channel 3: {msg.chan3_raw}")
                    logging.info(f"Channel 4: {msg.chan4_raw}")

    except KeyboardInterrupt:
        logging.info("Exiting program.")
    except Exception as e:
        logging.error(f"An error occurred: {e}")

if __name__ == "__main__":
    main()

The following is the output I got and it was stuck here and not moving forward.

INFO:root:Connecting to udp:192.168.8.1:14559...
INFO:root:Sending initial heartbeat...
INFO:root:Heartbeat sent.
INFO:root:Waiting for heartbeat from the flight controller...
INFO:root:Heartbeat received! System_ID: 0, Component_ID: 0