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Mavros rc plugin

ROS / ros eco / packages / mavros

Message Desc
RC_CHANNELS_RAW(35) The RAW values of the RC channels received (8 channels)
RC_CHANNELS(65) The PPM values of the RC channels received (18 channels)
SERVO_OUTPUT_RAW(36) The RAW values of the servo outputs
RC_CHANNELS_OVERRIDE(70) The RAW values of the RC channels sent to the MAV to override info received from the RC radio

RC_CHANNELS_RAW vs RC_CHANNELS

The different is that the rc_channel send the same information until 18 channels in one message, the rc_channel_raw send 8 channels in make if it from main or aux port

rc_channel has chancount field the mark the number of channels supported but the command return maximum of 18 channels

Mavros

mavros mavlink
/mavros/rc/in RC_CHANNELS_RAW / RC_CHANNELS pub
/mavros/rc/out SERVO_OUTPUT_RAW pub
/mavros/rc/override RC_CHANNELS_OVERRIDE sub

RC_CHANNELS_RAW / RC_CHANNELS

If rc_channels receive then rc_channel_raw dropped

RC_CHANNELS_OVERRIDE

Allows an external system like QGroundControl, MAVROS, or your own script to simulate RC transmitter inputs by injecting RC values directly into the autopilot.

  • Send at ~10–50 Hz for reliable override
  • ArduPilot expects regular updates or will revert to RC input
  • Use 65535 for any channel you don't want to override

Ardupilot

Ardupilot accept rc_channels_override only from gcs_id (usually 255)

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void GCS_MAVLINK::handle_rc_channels_override(const mavlink_message_t &msg)
{
    if(msg.sysid != gcs().sysid_gcs()) {
        return; // Only accept control from our gcs
    }

We need to start mavros with system_id 255

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/**/mavros:
    ros__parameters:
        system_id: 255

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[INFO] [1753461231.734660719] [mavros.mavros]: MAVROS UAS via /uas1 started. MY ID 255.191, TARGET ID 1.1

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ros2 param get mavros/mavros system_id
Integer value is: 255