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Excessive Lost Packets 3dr V2 Radios, Link quality <18%

Posted by Doug Andriuk on March 4, 2015 at 9:42pm

Using the link status in mission planner reveals that my connection is very poor.  RSSI is around 200 with very little noise.  The radios appear to connect fine and data does flow between the pixhawk and GCS, but the link stats shows that 4/5 packets don't make it.  I've replaced one of the radios, cables, etc but get the same outcome.  Any ideas?

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Tags: lost, packets, telemetry
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Replies

  • Developer
    Grant Morphett March 27, 2015 at 2:21pm

    Hi everyone.  Could I get some more info to try and chase the issue down?  There is obviously a problem as so many of you are experiencing it so we do need to find it.

    I suspect what some of you have suspected - that there is a bug in Mission Planner.  You could always download and run APMPlanner2 to see what it believes the packet loss is.

    The RSSI/REMRSSI and NOISE/REMNOISE values reported seem to be just fine and very unlikely to cause packet loss.  The SiK firmware for the radios hasn't changed in an age so that's unlikely to be it.  Which leaves the APM and MissionPlanner which change all the time.  I presume many of you have read through this page

    http://plane.ardupilot.com/wiki/common-optional-hardware/common-tel...

    and done the graphing analysis?  If there is a clear gap (the larger the better) between your RSSI lines and your NOISE graph lines you should be all good.

    Could I please get the following to do the analysis:

    Has everyone upgraded to the latest Mission Planner and if not could you please do so.

    What version of APM is everyone running in their vehicles - vehicle type would be good too i.e. rover, plane, copter?

    And critically could we get the dataflash logs and the tlog of a session running when the packet loss was very high please?

    Thanks, Grant

    • Greg Laabs > Grant Morphett March 27, 2015 at 3:03pm

      I will test and do all of this tonight. I currently have a ticket open with 3DR about this issue (#67514). I would be both a relief and frustrating to learn that it's simply a display but in Mission Planner!

      I'll do the tests and get the logs you asked for from my plane.

  • Tobias Witting March 27, 2015 at 1:02pm

    I found high packet loss with a v2 radio on my copter and v2 plugged into my laptop. The same radio plugged into an android phone gave 100% link quality. An old v1 radio works to 100% link quality both plugged into laptop or phone...

    • Emin Bu > Tobias Witting March 28, 2015 at 11:15am

      me to..on phone 100%...on pc 18%

      rage link 433 antenas

  • Michael Burmeister March 27, 2015 at 3:30am

    I believe this is a bug in Mission Planner.  If you check the Mission Planner logs you will see a number of lost packets.

    This is a bug where it is not calculating the next packet correctly.

    INFO MissionPlanner.MAVLinkInterface - lost pkts new seqno 216 pkts lost 255

     

  • MR60
    Hugues March 27, 2015 at 1:52am

    A possible cause for packet losses could be poor quality antennas and/or bad connection between the antenna and the RF chip (check the solder points between the antenna connector and its PCB solder points, check the antennas were not damaged such as a broken pin or a cbale that was bent too much, ...)

    It could also be due to unmatched antennas : it si fairly easy to confuse 900Mhz with 433 Mhz antennas as they all have the same external encasing.

    I've found that a simple home made dipole works much better than the default duck antennas that are shipped with the RF units.

    And of course, check all of your cables and connectors...

    • Marcin Krawczyk > Hugues March 27, 2015 at 1:55am

      OK, but this should be also visible via low RSSI value.

  • Greg Laabs March 25, 2015 at 10:09am

    I am having the exact same issue, but I found something even more strange: If I plug directly in to my Pixhawk via USB, Mission Planner STILL shows link quality at or below 20% (although it's much snappier so I am dubious).

    Have you tried plugging in directly to your flight controller's USB and seeing what Mission Planner says?

    • Mahesh M > Greg Laabs March 26, 2015 at 10:59pm

      Hi,

      I connected my APM 2.0 to the Mission Planner using the USB. MP shows 0 packet loss and link quality 100%. I am using Mission Planner 1.3.18.

      I did a flight with the same Autopilot and 3DR setup. I was able to fly about 200m away from the GCS. The link was ok throughout the mission.  The HUD RF signal strength indicator showed around 70% at this range.

      MP Link Stats still shows ever increasing packet loss when using the 3DR 433 MHz radio. Wondering whats wrong.

      Mahesh M.

      • Marcin Krawczyk > Mahesh M March 27, 2015 at 12:25am

        I've seen this case some time ago.

        We've tried a bunch of 433/868 modems (I'm producing them), all units seemed to be faulty due to high packet loss ratio.

        A the end we've found that the APM was the problem - same radio units connected to another one worked flawlessly. After firmware update/EEPROM cleaning APM was also OK.

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