Walkera Runner 250 Advanced - Runner250R-Z-14 - GPS and other modules

Discussion in 'Walkera Runner 250' started by Moguntia, May 31, 2017.

  1. Moguntia
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    Moguntia New Member

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    Please excuse if this will be a duplicate post and question - in this case point me to the correct discussion

    I'm new to Race Drones - I have flown for about a year a Hubsan X4 H501s advanced - and wanted to do a step up. So here I am - with a couple of questions

    While the Runner 250 is a nice modular system I can't locate manual/datasheet for the individual modules used on the quad. I'm mainly interested in understanding how each of the modules can be accessed and set/programmed if applicable.
    I do see micro SWITHCES - RES button - status LEDS !!! I assume that there is a document describing the functionality.

    To cut to the chase :
    As other before me: the GPS - hold position and RTH is no good.
    Used to this option on the Hubsan Quad - this worked like a charm - the drone would hover in position and using RTH it would land right in front of you.

    I read already several discussions in this forum - and yes I understand " I bought a RACE DRONE "
    Nevertheless based on the document this race drone does over GPS position hold and RTH and I have no luck.
    And YES - I already reset, reprogrammed, re-calibrated and did the voodoo-dance. I even bought a Devo F12e to make sure I'm not missing something.

    So what I found out - the MIX switch seems to work - at least on the OSD it changes from M to G to H.
    Also the GPS coordinates are correct - verified with GARMIN.

    Are there any other steps I need to take to enable the GPS ???
    I disassembled to GPS module - cable is good and connects through

    On the GPS module it self - there is a Coin Battery - what is the usage/function ???
    Current voltage is about 0.2V - don't think that this is correct.

    I really would like to understand and document this topic and take the guessing out of the problem

     
  2. bjr981s
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    bjr981s Moderator Staff Member

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    Interesting questions and as you asked so nicely I will help you.

    None of the individual modules can be programmed. This is a Ready to Fly model. Not a kit and not a development machine.

    You can update the FW on the flight controller and I recommend you do this to the latest supported version. 1.2

    The FW and instructions are in our resources tab at the top of the site.

    The only supported configuration e.g. PIDS and flight Parameters are those provided by Walkera as part of the FW upgrade process.

    Any changes to these settings will have unpredictable results. (Like changing the mixture settings on an old cars carburettor. its a hit and miss and most likely you will get it wrong if you don't know what you are doing.)

    The Runner (R) will not fly GPS stable out of the box.

    As you have done you must first calibrate the model.It is not documented but their is a limited time available for you to complete. If you don't do it fast enough it will time out and fail. There is no indication that the calibration has failed.

    You must do this on level ground. Start the calibration process, complete and place back on level ground before the timeout.

    You must also always take off from level ground do not ARM and takeoff from a slope. Also do not ARM the motors until you have a good 7 + sats in the lock.

    The RTH home location is set at motor ARM time so you can guess what happens if you immediately Arm with a lousy lock. You get a home position potentially in a different country.

    The calibration includes a RAW calibration of the compass. Make sure that you do this well away from any magnetic / metallic objects included the TX and mobile phones.

    Dont do it on a driveway or concrete surface that has steel reinforcements in the concrete.

    You only calibrate once. You only need to do it again if you move locations by 100 Miles +. Or Do a FW update.

    The Calibration (RAW) is further adjusted in the next few flights. You must do this in manual not GPS flight mode.

    Short flights power up, hover, do slow yaw rotations, land power down and do it again.

    Then takeoff in manual hover, switch to GPS mode and all should be OK.



    Cheers Brian


    p.s. The GPS stores the Sat identities and sky positions in memory. The battery is there to back these up but for only for a few minutes.

    This allows a faster lock time on a warm start as opposed to a cold start.
     
  3. Moguntia
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    Moguntia New Member

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    Brian,
    first of all - thank you for taking the time to read my post and provide guidance.
    I've spend some more time scrolling the forum archives - you are definitely answering the same question hundreds of times.
    So I hope you don't mind to take a look at the reflection of your response and some additional questions.

    MODULES on the Runner 250 Advance
    Understand - all modules are proprietary and allow in best case S/W updates.
    Nevertheless there are still some switches and LEDs
    • GPS Module – no updates, battery on PCBA holds data for a short period of time
    • OSD Module – DIP switch, 4 possible settings – is there a description/document what each of the settings changes ?
    • TX5816 Module - 5.8GHz downlink, DIP switch 8 possible settings - is there a description/document what each of the settings changes ? What does the LED indicate
    • RX710 – 2.4GHz downlink – button “clean”, guess this will reset the module to factory – What data is deleted ? Button LED – what information do I get out of the blink pattern
    • FCS250 Module – 3 LEDS visible – What is the meaning of the color and blink pattern
    • Power PCBA – in the front there is a single DIP switch, what is its function ?
    GPS HOLD and RTH – set up summary

    Compass calibration
    Basics are understood and also listed in the quick start
    • Calibration Time Window -> is there a value in seconds
      Seems odd that the user does not know how much time is given and there is no indication that the process failed
    No metal objects, No mobile phone, No Transmitter while calibrating
    • What is the required clearance between quad and the objects ?
    Level Ground
    • What is the allowed tolerance – before we call it a slope ?
    After successful Compass calibration [BTW -> what is the meaning of RAW]
    To finish calibration -> 3 flights
    Get the quad a couple of feet in the air – YAW slowly [around the quad center] – land and disconnect the battery – repeat at least 3 times
    For successful flight before arming the motors -> GPS need to show 2+ blinks or at least 7 SAT on the OSD screen.

    Question on GPS and Calibration
    I do understand the calibration requirement for the compass and gyro, so the quad knows his position in "space"
    Why is further calibration required in flight ?
    I would think once calibrated, the GPS and FC should communicate and keep the quad in place.
    Of course if the calibration was poor or incomplete, you might see some severe correction attempts.
    Yet my experience so far [i think I calibrated in timely manor] with 9+ SAT the quad would not keep heights and/or location

    Anyway planning to do exactly as you said this weekend ;)

    Cheers
    Frank

    I'm really sorry for all the questions which you might have already answered and I haven't found yet.
     
  4. Moguntia
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    Moguntia New Member

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    Update on above
    • TX5816 Module - 5.8GHz downlink, DIP switch 8 possible settings - is there a description/document what each of the settings changes ? What does the LED indicate
      Found a paper showing the DIP settings and related frequency
      Still need to know what the LED indicates - if any
      [​IMG]

    • Power PCBA – in the front there is a single DIP switch, what is its function ?
      Found in Quick Start V1.3 -> turning on and off the Video [must be the FPV camera
     
  5. bjr981s
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    Sure no problem. Look like you have already found a couple out yourself.

    If you document it all up in a single new thread when you finish I will set it up as a FAQ sticky.

    Some of these things are not documented anywhere so some you will need to just test your self.

    Some have been posted in other threads by members but I have not validated them. I have had no reason to adjust any.

    • RX710 – 2.4GHz downlink – button “clean”, guess this will reset the module to factory – What data is deleted ? Button LED – what information do I get out of the blink pattern. ( this is the bind clear button. It clears a Fixed ID from the RX. so then it falls back to promiscuous mode.}
    • FCS250 Module – 3 LEDS visible – What is the meaning of the color and blink pattern. Unknown to me.

    Raw is in, not very accurate. "Course" would be another description. The slow rotations in flight are the "Fine" tune.


    Basics are understood and also listed in the quick start
    • Calibration Time Window -> is there a value in seconds
      Seems odd that the user does not know how much time is given and there is no indication that the process failed.
    When you start the calibration the lights flash. When the time is up the lights stop flashing. Success or fail is all the same.
    You have to have the quad back down on the level surface before the lights stop flashing.

    No metal objects, No mobile phone, No Transmitter while calibrating
    • What is the required clearance between quad and the objects ?
    Not defined I would keep 10 metres away.

    Level Ground
    • What is the allowed tolerance – before we call it a slope ?
    1 Degree is a slope. The larger the slope the more uncalibrated the drone becomes.

    The Drone on power up calibrates the 3 Accelerometers and the 3 gyros as level.

    Now I will let you in on a little secret Something I learned doing Navigation so I could pass the tests for my license.

    GPS location is NOT ACCURATE to less than 2 metres. Most people think these are accurate to inches due to the behaviour of drones. They are wrong.

    This is a big problem when you are navigating reefs on a GPS Chart Plotter.

    The Drones rely on the fact that the inaccuracy is consistent in space. So it may be 6 feet away from where it thinks it is but 2 seconds later it is still 6 feet away in roughly the same place. This is where the flight logic and the gyros and accelerometers play a part.

    The Accuracy of a GPS signal is measured as a HDOP and VDOP value. Look them up on WiKi. These values change as sats go in and out of lock. The accuracy is basically dependant on the number of sats in the lock but their position in the sky is What provides the greater accuracy.

    Now what can happen its a key sat signal is lost and a new sat acquired and causes a 2 meter difference that is 2 metres away from the original position.

    If you watch a Time lapse video of a drone on a long hover you will see it jump about as sats come in and out of lock.

    If you look at some of the coding logic inside the FC you will see tests being performed like. The GPS says moved 6 feet but the accelerometer says no movement. Therefore ignore and re-baseline the GPS coordinates.

    So its a complex dance between the GPS the Gyros and Accelerometers.

    So what can upset this dance. and cause flyaways.

    • Weather conditions causing interference with GPS signal.
    • battery brownouts. Over discharge of batteries
    • Vibration. e.g. non balanced and nicked props.
    • Bug in FW. Executing untested code due to unexpected parameters.
    Lastly. GPS is only used for horizontal positioning. The virtual accuracy of GPS is woeful. the VDOP number is way too high.

    All drones that hold height / altitude do so with a barometer / altimeter.

    They are suspect to wind if not protected correctly and to weather patterns like thermals.

    They can be generally be found in the Flight Controller.

    The importance of the compass is also not well understood. It most cases it does little other than tail hold with the gyros and accelerometers.

    Its primary use is doing a Return to home. And loss of signal from the TX generally causes a RTH

    So if you have done all the right things and calibrated. Waited for the sat lock before arming motors you are still at risk if flying near a magnetic anomaly. e.g. power lines.

    If you lose signal and it initiates a RTH the model knows were it is within 2 metres it know where home it is within 2 meters. It calculates a compass bearing to home and whoops bearing is wrong as compass is effected by either mag anomaly or no calibration near the anomaly. So Model fly away.

    Hope this helps.



    Cheers Brian
     
  6. Moguntia
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    Moguntia New Member

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    No problem to do the summary of our conversation - need a little bit to play with the drone and collect data.

    Before I start plying and screw it up - what can I set on the OSD ???
    • OSD Module – DIP switch, 4 possible settings – is there a description/document what each of the settings changes ?
    GPS and the uncertainty :D
    Well - the precision and accuracy of the GPS is well understood.
    If you do GeoCaching you learn this the hard way :mad:

    I take your explanation and will think about it. Agree with the described problems and causes for failure.
    I would also assume the barometric and GPS altitude is correlated for accuracy.
    The part I'm not so sure, is RTH via compass - the FCS has the GPS starting point and a current position [with some failure] therefore the compass compared with GPS location should allow for a very straight flight home.
    I'm using for my argument the published data for RTH which considers distance from home point to decide on return heights.
    But again - once I'm confident about the GPS -> I will give it a try.

    Side question: as I mentioned in the first post - used before a Hubsan H501s, aside that the FPV on a return flight was snow, the actual ease and accuracy of the GPS calibration, hover and RTH was impressive.
    Hubsan has done something right in this case, while other options are a reason to change ;)

    Cheers
    Frank
     
  7. bjr981s
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    GPS is not used in any way for altitude.

    Are you sure the OSD has 4 switches? I have no detail on this other than there is a switch to turn it off.

    The point about the compass is if you are near an anomaly or the compass is not calibrated correctly. The bearing will be inaccurate.

    So if the FC determines that 60 degrees its the way to home point then it will use the compass to fly bearing 60 degrees but if the compass is near an anomaly the bearing of 60 degrees could be 250 degrees.
     
  8. Moguntia
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    Moguntia New Member

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    Confirm - Runner 250 OSD Module – 2 DIP switch, allowing 4 possible settings – is there a description/document what each of the settings changes ?

    OSD Module Runner250.jpg
     
  9. bjr981s
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    Single dip switches are hard to by. One of these does nothing the other turns it off.

    Most dip switches other than channel select are not binary so each position only 1 function.
     
  10. Moguntia
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    Moguntia New Member

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    Function of the DIP understood and found the same info in a German written guide.

    Nevertheless - today I tried to get the GPS Hover and RTH on the quad established.
    So I did the full Voodoo Dance - and no good - not even close to a position hold.

    Followed the instructions as follows

    1. Selected a wide open field, no power lines, no obstacles, no wires in the ground
      Condition: clear skies 3 to 6 mph wind from the west
    2. Take-off board and level - ensured plain starting ground
    3. Timed the window for calibration 3x -> start blink to end blink -> 30sec it is
    4. Placed the Remote 20m distance from the Quad
    5. Power up the quad -> Power up Remote -> wait for proper connection and 4 GPS blinks
      -> start calibration process -> finished in time.
      Therefore I assume task completed
    6. Power down Quad and Remote
    7. Power on Quad and Remote -> wait for 4 GPS blinks and set MIX to manual -> arm the motors
      -> take off and YAW 360. [brought the drone about 5 to 10 m into air and turned around the center count clock wise]
    8. Did steps 6. and 7. four times.
    9. Powered Quad and Remote up and started in manual mode, brought power to 50% and switched to GPS
      Quad simply drifted away no attempt noticeable for correction of position.

    Did the above sequence with 3 different batteries - same result.
    Somewhat frustrating -> I would say now not functional if this sensitive
    There is now feedback at all from the Quad about success or possible failure mode.

    Any further suggestions ??
     

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