So I read an interesting article about GPS antennas called "Adding a GPS Chipset To Your Next Design Is Easy".
A few points to bring up that I have concerns with dealing with my M8N antenna.
1. Active vs Passive Antennas. Two paragraphs within the article describes the difference between Active and Passive antennas. According to CSG Shop's specification for the NEO-M8N it comes with a low-noise regulator and RF filter built-in. So I'm assuming that it is a active antenna.
2. Antenna's requiring adequate plane. If I read that document correctly, these GPS modules may require a GPS plane as they are installed on a PCB that does NOT have 40mm of side to them.
Quote: "Generally, patch antennas in the 15- to 25-mm size range with a least a 40-mm (on a side) ground plane will give the best performance in portable equipment, but this may be too large for your application. This could force you to look at smaller antenna topologies such as linear chip antennas."
3. The next concern is to mitigate the noise interference from FC, ESCs, and PDB. Since my Y6B is set up with a clam shell cover and my M8N is attached under and close to the all the electronics, I may need to develop a shield "ring" connected to the shield can and then connect that ring to RF ground through an inductor at a single point.
Quote: It's common in VHF and UHF RF shielding to connect all points of the shield can to the PCB's ground plane. This can be a mistake at GPS frequencies, since the open-air wavelength of a GPS signal is so much shorter than UHF. Depending on the size of the shield can, if there is current flow across the can, the shield can will be able to resonate near GPS frequencies resulting in interference or de-tuning of the GPS RF.
By developing a shield "ring" connected the shield can and the inductor, the inductor will filter any EMI-induced current flow. The ring connected to the shield can will prevent any current flows or resonation issues.
I'm not an electrical engineer and need guidance from those out there who are. Did I interrupted this correctly? and if so I could use some help with developing the "ring".
Thoughts?
Replies
@AKcopter,
I think it's best to contact CSG Shop and request if they have schematics for their boards. Once we have this, it should be easy to soldier the ground plane.
Never had Bad GPS messages either ...
Hi AKopter,
I never had "bad GPS health" messages. Does this occur frequently? Maybe a cable problem?
Yeah...
It does, if you have a look at the log you will see that even though I am in an open ground with horizon visibility of about 15-20 degrees elevation from the ground...
sats are 18-21 and hdop 1.1-1.4
I will check the wiring to see if its a problem..
right now I have two GPS modules and I have found that I get bad GPS health messages when I use the Rctimer GPS, this may be because they have a different connector than the one I used with my CSGshop GPS, on my CSG GPS I have used DF13 connectors
I will do some more testing today and let you know if its a wiring problem..
In all likelihood it isn't coz' I have been very careful about the integrity of cable connections on my hawk
naitsuga
You should perhaps look the correct post before complaining ....
Two days ago Rob Lefebvre reported that 3DR decided not to use M8N GPS , so nothing new
However, VirtualRototix is running Arducopter 3.2 code wich they ported to their VRbrain autopilot.
They also developped their own "M8N+compass" board
Two flights with 2 quadcopters (in the same area and with the same mission ) were done by Marc
which analyzed the logs
Both flights were successfull
First one with M8N from VR showed INAVERR increasing during flight from 0 up to 255
Second with M8N from RTF showed INAVERR increasing during flight from 0 to 20
tshado
I think you have to revisit your post linking to ( http://www.rcgroups.com/forums/showpost.php?p=31022247&postcoun...) that is Slimething's post not John Dennings'ss one that he linked on Github.
Now I know that 3DR GPS have issue too. but we don't know which one ?
for sure he stated that He has seen the same issue (at least once) with the 3DR GPS.
3DR is selling LEA 6H, is that the same that JD's have when the INAVERR shoot up?
Thank you JD for opening the ticket
Can you let us know the GPS module you have, was that LEA 6H or previous model one?
I
Doug> So far I have not heard of any compelling proof that someone's UAV has crashed or flown away due to excessive INAVERRs.
That is my current assessment too. As far as my personal experience goes, I've got about 300 flights on m8 (unshielded) all performing flawlessly. So not only no crash or flyaways, but actually very good position hold, flight precision, etc ... This includes relatively high speed flights at 50mph+.
I only started looking at INaverrs after this issue came up recently, and found that most of my flights started with high INAVerrs but the value then remained constant during the flight. I did find a couple instances where it did jump up *during* flight, hence my current (and only) concern, but again the flight was flawless. And in a few instances, inaverr starts at 255, so I have no idea wether there were further misses.
Naitsuga>: 3DR is selling LEA 6H, is that the same that JD's have when the INAVERR shoot up?
I've seen INAVerr shoot up in flight with both M8 and the 3DR gps, so yes. In the m8 cases it was not an issue flight wise, no degradation whatsoever. I don't think it wasw an issue either in the 3DR gps case, but this was a while back and I am not so sure as I don't remember the flight as well. One thing, though, in that 3DR GPS case: log shows that INAVerr shoots up, yet GPS hdop and nsats are constant while this happens, indicating there's no gps glitch or anything abnormal.
http://www.rcgroups.com/forums/showpost.php?p=31021305&postcoun...
http://www.rcgroups.com/forums/showpost.php?p=31022059&postcoun...
@John Dennings ,
Great, this ticket will be a good way to follow about this INAVERR reported in logs
Hoping to understand if it is indicating real functionnal error which could create flight failures , or if it is a performance problem of arducopter code not getting GPS updates every 200ms
Keep in mind that there is a possibility of a missed report or even a corrupted report which could be ignored by the code on the Pixhawk FC thus showing as an INAVERR. I'll say for the record that I could be wrong with this assumption and testing needs to take place to answer this assumption. But if it's true then at what number of failed reports does it cause navigation failure while in autonomous mode?
So far I have not heard of any compelling proof that someone's UAV has crashed or flown away due to excessive INAVERRs. How is the code handling the quantity and is there a safety net built in to help with a fly-away? I'm not sure. And what if I have two GPS units, one a NEO-whatever and the other a NEO- or LEA-6H unit? Does the error rate decrease, stay the same, or becomes worse?
Tests need to be conducted systematically and without bias to produce factual data and that is a tall order. 3DR does not have the time nor interest (I'm sure) to hammer this out. I think the best we can do is work collectively to obtain the data and make logical conclusions. From what I'm seeing in various discussions, this is happening, although somewhat disorganized.
I'm open to ideas and suggestions on extrapolating the data if there is enough folks who wish to come together and develop a test plan and implement it without bias. Any takers?
Not to sound disgruntled, but I brought this matter up on January 31, even though it didn't start out about INAVErr. It garnered little interest for over a month. I wasn't looking for a fix, just wanted to know if it was a problem and why it's buried under PM and why, if 255 is bad, why it isn't flagged as a failure in the diagnostics drop down.
There are several discussions going on at RCG about this issue in various threads trying to find out what the number 255 represents and who was having problems using the M8N. Honestly, not one person has reported problems related to high INAVErr numbers. Some, or many by now, are concluding the INAVErr is as big a red herring as the loop errors because nobody has actually reported a crash or flyaway due to high INAVErr numbers. Of course up until recently very few knew it existed, so that may not mean anything.
Craig Elder said he's been trying to explain for months to people the M8N in it's bare form has problems, but I could not find any useful information concerning INAVErr before first posting two threads on the subject in late January. I literally had zero knowledge about INAVErr until later on, but still haven't seen the section of code that calculates the values. Fortunately a few others reported high INAVErr (and gaps in the time stamp/KMZ) and finally thanks to AKCopter's one simple question in an unrelated thread, Craig Elder spelled it all out......mostly.
http://diydrones.com/forum/topics/csgshop-neo-m8n-is-giving-pm-errors
http://diydrones.com/forum/topics/inaverr-is-it-the-gps-or-fc-or-ne...
At RCG several times as well, when it particularly came to a head in the RCTimer M8N thread here
http://www.rcgroups.com/forums/showthread.php?t=2353323
Also at Arducopter Support forum- zero responses after two posts. Bionicbone, creator of APM Flight Log Analyzer also posted last year with no response.
What really bothers me is CSGShop brushed it under the rug when I emailed them weeks back and their knee jerk response was to blame Pixhawk, and didn't even attempt explaining why.
Before considering any mod, I want to know what could and "should" happen getting these high INAVErr numbers. Why is it actually a problem? Seriously. I still can't prove the occasional twitching is anything but a tuning problem. I've had the copter stay dead still for 2 minutes several times ~6 ft off the ground, all the while with INAVErr holding at 255. How do we know it's electrical noise from the other components and not just noise from the added satellites (TMI)?
Apologies for the rant. I understand and appreciate the hard work the devs put into Pixhawk, which I really like a lot. It's probably asking too much for them to get more involved, but IMO the LEA-6H has run its course and needs to be replaced by a better GPS system.
Read this post at RCG. He had two completely diverged INAVErr results with two different M8N's, but also no problems with either in the flights.
http://www.rcgroups.com/forums/showpost.php?p=31027662&postcoun...
-
11
-
12
-
13
-
14
-
15
of 15 Next