Sending String Over Mavlink

sripad_sahu · June 26, 2018, 7:42am

Hello,
I want to send A String from my GCS to arduplane. Does Mavlink allow sending of characters and string???

Thank you,
Sripad

peterbarker · June 26, 2018, 10:43am

I want to send A String from my GCS to arduplane. Does Mavlink allow sending of characters and string???

STATUSTEXT

ArduPilot/mavlink/blob/master/message_definitions/v1.0/common.xml#L4242


      
          <message id="4" name="PING">
            <deprecated since="2011-08" replaced_by="SYSTEM_TIME">to be removed / merged with SYSTEM_TIME</deprecated>
            <description>A ping message either requesting or responding to a ping. This allows to measure the system latencies, including serial port, radio modem and UDP connections. The ping microservice is documented at https://mavlink.io/en/services/ping.html</description>
            <field type="uint64_t" name="time_usec" units="us">Timestamp (UNIX Epoch time or time since system boot). The receiving end can infer timestamp format (since 1.1.1970 or since system boot) by checking for the magnitude of the number.</field>
            <field type="uint32_t" name="seq">PING sequence</field>
            <field type="uint8_t" name="target_system">0: request ping from all receiving systems. If greater than 0: message is a ping response and number is the system id of the requesting system</field>
            <field type="uint8_t" name="target_component">0: request ping from all receiving components. If greater than 0: message is a ping response and number is the component id of the requesting component.</field>
          </message>
          <message id="5" name="CHANGE_OPERATOR_CONTROL">
            <description>Request to control this MAV</description>
            <field type="uint8_t" name="target_system">System the GCS requests control for</field>
            <field type="uint8_t" name="control_request">0: request control of this MAV, 1: Release control of this MAV</field>
            <field type="uint8_t" name="version" units="rad">0: key as plaintext, 1-255: future, different hashing/encryption variants. The GCS should in general use the safest mode possible initially and then gradually move down the encryption level if it gets a NACK message indicating an encryption mismatch.</field>
            <field type="char[25]" name="passkey">Password / Key, depending on version plaintext or encrypted. 25 or less characters, NULL terminated. The characters may involve A-Z, a-z, 0-9, and "!?,.-"</field>
          </message>
          <message id="6" name="CHANGE_OPERATOR_CONTROL_ACK">
            <description>Accept / deny control of this MAV</description>
            <field type="uint8_t" name="gcs_system_id">ID of the GCS this message </field>
            <field type="uint8_t" name="control_request">0: request control of this MAV, 1: Release control of this MAV</field>
            <field type="uint8_t" name="ack">0: ACK, 1: NACK: Wrong passkey, 2: NACK: Unsupported passkey encryption method, 3: NACK: Already under control</field>
          </message>

Sripad

Peter

sripad_sahu · June 26, 2018, 11:06am

Thank you @peterbarker for the quick reply.
I was able to send the message using STATUSTEXT from a python script.
I used this :
drone.mav.statustext_send(mavutil.mavlink.MAV_SEVERITY_NOTICE,“checking”);

Now I am stuck at receiving the message in the autopilot. Could you help me with that?

Thank you,
Sripad

peterbarker · June 26, 2018, 11:01pm

Thank you @peterbarker for the quick reply.
But I think STATUSTEXT is used to send data from autopilot to gcs. I need the exact opposite.
e.g : I need to send “qwerty1234” from mavproxy(GCS) to my autopilot.

Your GCS is just another mavlink system. It behaves a little differently
to a vehicle, but can send and receive the same messages.

If it is possible so please can you give an example or tutorial to do this.?

If you address a statustext packet to and ArduPilot vehicle, it will log
it in dataflash.

This is the member function which handles the incoming statustext:

github.com

ardupilot/ardupilot/blob/master/libraries/GCS_MAVLink/GCS_Common.cpp#L1930


      
                              chan,
                              try_send_message_stats.behind);
              try_send_message_stats.behind = 0;
          }
          if (try_send_message_stats.fnbts_maxtime) {
              gcs().send_text(MAV_SEVERITY_INFO,
                              "GCS.chan(%u): fnbts_maxtime=%uus",
                              chan,
                              try_send_message_stats.fnbts_maxtime);
              try_send_message_stats.fnbts_maxtime = 0;
          }
          if (try_send_message_stats.max_retry_deferred_body_us) {
              gcs().send_text(MAV_SEVERITY_INFO,
                              "GCS.chan(%u): retry_body_maxtime=%uus (%u)",
                              chan,
                              try_send_message_stats.max_retry_deferred_body_us,
                              try_send_message_stats.max_retry_deferred_body_type
                  );
              try_send_message_stats.max_retry_deferred_body_us = 0;
          }

At that stage we know the message was “aimed” at us.

Sripad

Peter

borhanreo · July 30, 2019, 7:49am

Hi,
I am trying send string over mavlink.

data = "VIBRATION {time_usec : 6973068444, vibration_x : 0.0256990697235, vibration_y : 0.0270975790918, vibration_z : 0.043224286288, clipping_0 : 0, clipping_1 : 2, clipping_2 : 0}"
autopilotout.mav.send(data)

But i am facing error
'str' object has no attribute 'pack'