Home lock position question
- Thread starter pjw73nh
- Start date
Dadcat said:
This is good info to know. I need to check back in my correspondence to see where the idea that it was bypassed when power was applied by the flight battery came from. While I never got a concrete answer on how long it should last, the impression was that the current draw from the module was published, and would have to be compared with the reserve capacity of the battery. Even if only for an hour after a 7 minute flight, it would provide warm start after the first flight, and TTFF should return to the 1 second spec. As long as the almanac and RTC calibrations were retained, it should be good to go quickly after the first battery change.
Dadcat said:
It also saves the Real Time Clock calibrations that offset the warmup time of the TCXO so the time differentials are more correctly measured at startup.
When questioning uBlox concerning battery draw down from keeping the TCXO hot, it was revealed that it powered up on the main battery, and the RTC calibrations were necessary as the TCXO came up to temp and the time base stabilized.
While it is impossible or it to retain locations while not powered, the saved data helps predict availability - based on UTC.
HI, new to forum.
Phantom Vision 2 and Vision 2 plus.
While the manual is not the best, I found You Tube to be very helpful in learning to fly these copters.
fly safe, have fun
Radar
Phantom Vision 2 and Vision 2 plus.
While the manual is not the best, I found You Tube to be very helpful in learning to fly these copters.
fly safe, have fun
Radar
Interesting discussion. Very informative.
To take the discussion in a slightly different way, but still on-topic, how does the loss of GPS affect the "find my phantom" function?
Let's say you are flying your phantom a considerable distance from you and say 1000 feet up. You lose GPS (say you only have 4) and then lose control function. The aircraft then begins drifting with the wind and say lands 2 miles away.
Is four satellites enough to maintain location function? Or will the find my phantom only show the last position it had significant GPS coverage.
To take the discussion in a slightly different way, but still on-topic, how does the loss of GPS affect the "find my phantom" function?
Let's say you are flying your phantom a considerable distance from you and say 1000 feet up. You lose GPS (say you only have 4) and then lose control function. The aircraft then begins drifting with the wind and say lands 2 miles away.
Is four satellites enough to maintain location function? Or will the find my phantom only show the last position it had significant GPS coverage.
Cocoa Beach Kiter said:
My understanding is if your sats drop below 6 and you have S1 up, it will switch to ATTI mode. If you then lose TX control, RTH will auto land straight down from where it is. You can of course try to regain TX control with S1. Find My Phantom will show the last good GPS position before your sats dropped out as long as you maintained telemetry the whole time. If you lose telemetry, the position shown will be the last GPS position when you had both telemetry and sats > 5.
N017RW
Premium Pilot
Dalite said:
Where do you see this information?
From what I read abut the NEO-6Q the backup battery (if connected or not dead) is there to maintain the RTC and RAM only.
Also, by classification, TCXOs are not contained in an 'oven' to maintain a constant temp.
They contain additional elements to measure and 'pull' or adjust the oscillator's output accordingly.
It sounds like your describing an OCXO or oven-controlled crystal oscillator.
I don't see any reference to that in uBox's data sheets.
But I'm always open to new or updates to information so please share if you wish.
Cocoa Beach Kiter said:
In DJI/Phantom system: NO.
6 satellites is the minimun to get GPS fix. On this matter the DJI documentation is pretty clear.
I think what he is asking is:
Yes I think we understand the Phantom needs 6+ sats for the GPS info to be passed on to and used by the flight control system.
But what I believe he is asking is: "Is 4 sats enough for the "find my phantom" function to operate ?". I do not have the answer but would certainly like to know.
Just my $.02.
Yes I think we understand the Phantom needs 6+ sats for the GPS info to be passed on to and used by the flight control system.
But what I believe he is asking is: "Is 4 sats enough for the "find my phantom" function to operate ?". I do not have the answer but would certainly like to know.
Just my $.02.
pjw73nh said:
4 sats is not enough to get a "GPS fix" i.e. to know where it is. So, if the Phantom does not know where it is, it cannot tell its location to the Vision app, which is used for "find my phantom" function.
Just my €0.01
N017RW said:
The Temperature Controlled Xtal Oven is a Temperature Controlled frequency standard. Al least, that is how it functions in the communications gear I used on NTIA spectrum that had to meet frequency stability specs. Keeping the TCXO hot assured stability at power up. Some design aproaches used a warm-up period to come up to temp and resulting stability. I first thought that the TCXO could be drawing the battery down, as the gear I had been using for comms kept it hot all the time. The most simple way to diagnose a stability panel was to feel the side panel that the TCXO was under to see off was working. Cold was a nogo situation.
After pouring through most of the NEO-6 documents, I contacted them with a series of questions to try to understand a little more about the configuration. My correspondence corrected some incorrect assumptions and confirmed some others.
Their implementation of the TCXO is a frequency standard for the RTC. It is only brought to temperature when the main battery is inserted and powered on. RTC calibration data is created as the TCXO warms up and increases RTC accuracy. So, I found that wasn't a dead BBRAM battery cause. The RTC accuracy is critical to compare to the GPS time data to determine distance ( time differentials). Until the RTC calibrations were completed, the GPS data produced errors that decrease as the RTC accuracy increases.
As far as predicting availability, the Almanac, when properly stored, along with the RTC offsets as the TCXO achieves max stability are much like using Kepelarian Elements to predict a satellite pass. I spent a good bit of time in the early 1990s learning how to communicate through low earth orbiters, the space shuttle packet robot and later the ISS APRS robot. Since they are all elliptical in orbit, there had to be a way to remove guesswork and point antennas to the right bird at the right time. I equate the Almanac and accurate time base to be the equivalent. It doesn't aim antennas, it just helps limit the focus to what should be visible at the time of flight. If the battery is dead, or charging to above minimum usable voltage, the GPS performance is slowed until this critical info is created RTC (calibrations) and downloaded ( almanac). On consecutive flights, it is retained ( thanks to Dadcat for getting that sorted out)
This could all be an absolute leap in the wrong direction, but it is what I gathered from what I knew and thought I knew. Since there is too much worry about being copied or revealing who was copied in these hobby applications, there is very little in the way of a manufacturers flow chart to base proper operation on. With that in mind, I fully accept that my understanding may change as more concrete data is found and shared.
4 satellites may or may not be enough to get a reasonable position estimate. It depends on where the satellites are located relative to each other. If they are lined up in a "row" overhead, probably not.pjw73nh said:
What I do know, from seeing it happen, is that the phone app shows "N/A" for distance if the Phantom only sees 5 satellites while flying. I assumed this would mean the "Find My Phantom" function is not being updated either. I suppose it's possible it may still be getting updates. I'm sure the GPS is still calculating a position (and most likely an accuracy estimate) and reporting it to the board the Naza unit is attached to.
What the brain decides to do with that information, I do not know. Maybe the <6 satellite position information is still being sent over wifi and it's the phone app that decides not to show it.
N017RW
Premium Pilot
Dalite said:
I'm sorry I can't accept most of what your saying here because it is not supported by mfg. documentation.
After further review, the NEO-6Q module actually includes the optional, discrete RTC XO.
The subject TCXO is only used for the RF Front-end (demodulation between antenna and baseband processor).
But this makes me think you're not to sure yourself:
"This could all be an absolute leap in the wrong direction, but it is what I gathered from what I knew and thought I knew."
Let's not waste anymore calories here.
Cheers!
If one loses his/her phantom, will the app retain the last known GPS location of the phantom even if you close the app and re-open the app the following day to do another search of the phantom? Just curious in case this were to happen, and unable to find the phantom, I would not want to lose the location data. Of course, one could always do a screen shot. I'm assuming the gps coordinates are at least provided via the app...
AnselA said:
I understood that regarding the Quads functioning. I wasn't sure if that was the case for find my phantom positon info.
srandall25 said:
That's very easy to test by yourself. Just restart the app after Phantom power off.
Dalite said:
To ElGuano and all,
I spent the better part of the day trying to retrace my steps in forming the hypothess about the TCXO stabilizing the RTC. that is simply incorrect. In looking over the documentation in detail today, I find that the RTC is crystal fired and the TCXO serves as a receiver stability component ( exactly what was presented in another response) Looking back at time or differential based location techniques, the theory had merit; but not so in ths case.
The TCXO is calibrated during operation, and those calibrations are stored in BBRAM; but not for the benefit of the RTC.
My apologies to all that took it at face value and let it guide their comments.
Since there's already a home lock thread I'll ask my question here.
Am I the only one who struggles to get S2 to initiate a home lock?
I've tried frantic flicking, slow flicking and partial flicking. Nothing!
What am I doing wrong?
Am I the only one who struggles to get S2 to initiate a home lock?
I've tried frantic flicking, slow flicking and partial flicking. Nothing!
What am I doing wrong?
RPA said:
Do you mean "resetting home location/position/point" or "switching to home lock flying mode"?
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