Replies to This Discussion

Permalink Reply by Jonathan M on May 22, 2012 at 8:14am

I tried powering via USB with no peripherals connected and let it sit for 30+ mins outside.  I was getting 5-7 sats consistently, but there was no lock.  9999hdp as well.  The blue light was blinking a bit faster than it had previously.  Updated to the latest firmware as well with no luck.

I am using just an ESC bec for APM power when connected to a lipo.  Again, I did not change my setup at all.  It just stopped getting a lock in the past few weeks.  My thinking is that it's a hardware issue.

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Permalink Reply by Grant Olivier on May 22, 2012 at 10:37am

Just to report back on this issue for me.

I have replaced my MediaTek GPS modules on the APM2 with the uBlox GS407 GPS and the DIY drones uBlox adapter which lock every time within 2 - 5 seconds regardless of how I power up the APM2 (ESC/BEC, USB, NiMh, input/output rails etc). I have reserved the MediaTek GPS unit for use on the UDB4 which work reliably. I am more convinced that its a timing issue on the APM2 firmware or a software bug for the M-Tek GPS or failing that the M-Tek GPS may be very sensitive to supply power thresholds. I still need to go in and measure the supply rails with a scope to test the latter hypothesis.

Happy hunting, I see there are many people out there with this problem and I am looking forward to finding (or hearing) a definitive problem an solution.

Regards

Grant

 

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Permalink Reply by Michael Müller on July 6, 2012 at 1:55am

Hi Grant, I have the same issue with the GPS and now I consider to replace the MediaTek with an uBlox like you did.

Would you please explain how you set it up? Was it difficult? Was it necessary to deactivate the MediaTek?

Thanks.

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Permalink Reply by Karl on May 23, 2012 at 4:12pm

The main issue that I found with the onboard GPS is that it is sensitive to anything that can shield the signal, which is above the GPS module (even the odd RC cabling) and secondly the proximity of the reciever, which in my case Optima 7, due to the transmission of data back to the controller this was also impacting the GPS lock and consistency. Basic sugestions would be to remove anything above the GPS module (including any carbon fibre) and make sure that your reciever unit (if it's not purely passive reciever) is not too close or below the horizon of the GPS board.

Since moving things around and making sure my GPS has a clear sky I always get a lock in under a minute and never loose a GPS lock during flight. The one other element is that a loss of GPS lock during auto makes the waypoint navigation very messy (plane goes into circle mode and then back into auto after a half loop)

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Permalink Reply by George on June 11, 2012 at 5:08pm

Contrary to my previous comments on this issue, I withdraw my comments of "Mines fixed" and repost as "still suffering" and, I am sure this is a power related issue. Having used the J1 jumper solution I posted earlier as a work around never getting lock, last night while doing some bench work, I noticed a glaring difference between the GPS operation under different powering conditions.

If I power the APM2 with the USB, as I was for grabbing logs and setting parms, I get a quick strong lock with the on-board GPS, 7 - 9 sats in under 2mins, cold start, in my shed, with spaghetti junction around the APM as it always is with my builds. 3DR telemetry radio (915) is running, although with nothing to talk to, minim osd is also powered up although the Vtx (1.2/500) is not powered up.

I now disconnect USB and power unit with the flight pack LiPo. The front end of APM is powered from a dedicated Ubec, via the dragonlink Rx. The output rail is powered via a CC 100amp ESC BEC. Again 3DR telemetry is running, in this case it is talking to the ground station unit, again Vtx is not powered. Dragonlink Tx is a good distance from aircraft to eliminate any interference it may produce. I can not obtain a 3D lock in this condition.

My thoughts:

1. Noisy power? I doubt it's any more noisy than USB power, video/osd show no signs of bad power when running. Is the USB port any more filtered than the input/output rails?

2. 3DR telemetry is having an effect while locked/communicating with ground station? I have tried with air module disconnected and although I could not see sat number or hdop, the lock light never went solid.

3. I have exactly the same GPS module within 30mm of the APM unit, used as a stand alone GPS receiver for my AAT, it locks solid every time, from the same power supply.

I don't really have a direction to head with this now. I think it is time to hack the board. Piggyback the Tx line from the AAT GPS onto the Tx trace of the APM GPS??? Reckon that will work? 

The subject has gone fairly quite, given quite a few members show signs of these symptoms, and solid GPS lock is reasonably important. did I miss a fix on this? The link to the issue raised, has now been closed as "Not software related".

   

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Permalink Reply by Owen Booth on July 12, 2012 at 4:01am

Im with you George, I get lock with 5v or more going into apm,(USB or dedicated BEC) but only 2 sats using esc input. I too believe its a power issue. There are a lot of people hijacking this thread with dick measuring, & hardware bagging. Can we concentrate on being an OPEN community & working together for some forward progress please?

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Permalink Reply by George on July 12, 2012 at 4:18pm

Not sure [reads 'cant remember'] if I posted this elsewhere Owen, but further testing I did has led me to install an LC filter on the power supply line, directly before the APM. I 'tuned' the filter (just tried a few different cap values) and the end result is quite good. I have got the GPS performance to within about 85-90% in a flight scenario, compared to when just plugged into the USB. I'm not one to investigate much further, as now it works, it's fit for purpose so I've moved on to all my other issues, it does however indicate IMHO that, with all other issues aside (RFI, EMI etc.....) noisy power remains at the top of my mind as the cause, however the root cause may lie in the front end power handling of the APM hardware. I shall leave that to be determined by those more edjabicated than me but.   

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Permalink Reply by Alex on June 11, 2012 at 5:17pm

I seem to every now and again get a lock on the GPS, but not on the APM2 itself... a reset seems to clear this.

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Permalink Reply by Bruce Jones on June 11, 2012 at 11:38pm

I went out tonight for the first time to fly my APM2.  I waited for about a half hour under clear skies in the middle of the country to get a GPS fix and couldn't.  My cell phone and car GPS each had no problem finding 7 satellites.  This was with my normal flight power system - LIPO connected via ESCs.  So I went ahead and flew (not a bad maiden!) and 15 minutes later when the battery was low, I noticed when I landed that the GPS blue light was on solid.

Just out of curiosity, after totally powering down the craft I plugged it back into the USB to see if I could get satellites.  I waited about 20 minutes and it had still found only 2 satellites.  I went and flew two quads and sure enough, when I came back about a half hour later it has a GPS fix.  I then flew it and played around with loiter (and had more issues, but that's a separate topic).

Am I REALLY going to have to wait 45 minutes for a GPS fix every time I want to fly this thing?  Grrr....

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Permalink Reply by Jonathan M on June 15, 2012 at 11:30am

I really don't understand why the GPS lock is an issue now.  I never had issues the first 3-4 months of use with my APM2.  All of a sudden it just stopped getting a fix.  I am not sure why and it's super frustrating to not be able to use the loiter and auto function anymore.

I really am out of ideas. 1.5+ hrs of 6-7 sats with no 3Dfix.  And for some reason now, my APM isn't reading the datalash, so no logging capability. Sigh..

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Permalink Reply by Michael Müller on June 28, 2012 at 8:11am

I have the same issue: GPS-Lock only when powering via USB. Is there any solution meanwhile?

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Permalink Reply by Zachary Eldridge on June 28, 2012 at 8:23am

It downloading the almanac again just have it sit outside for hour or two. Once you get a lock you can unplug it then repower it should get a lock 30-60 sec. I had this problem before and realized this helped.

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