My Pixhawk died (from heat exhaustion I think) so I got a new one from GoodLuckBuy, and it was so cheap I got a new GPS unit, an M8N to replace my LEA6H.
I did a preliminary test and was getting 8 to 11 satellites in the middle of my living room, so I thought it might be good to go. So I put it all back together and battened down the hatches and connected with MavLink. No satellites.
Li'l bit o' Googlin' and I found out about u-Center and how to connect to the M8N over TCP. Did that with mixed results, u-center was getting some information, but still no satellites.
Then I noticed that between connecting with u-center and rebooting Mission Planner because it kept crashing, it would get enough satellites to fix its position more or less, though it was only getting 6 or 7.
But then when I connected with u-center again, it would go a-traveling, eventually making its way through the Panama Canal from the Gulf of Mexico.
I tried uploading a settings file from 3DR to the M8N, but that was a no-go, then I tried downloading from the M8N to see what it already had, and it said there was no connection, even though u-center was getting coordinates from the unit.
At this point I'm getting a sinking feeling in the pit of my stomach, so I shut down the software and unplug the Iris+, set it up next to my living room window, then plugged the battery back in.
BOOM! In seconds I get a green light, 12 satellites, 15, 17! Then it goes blue again for a few seconds, then green again. So I hook up u-center again, and the light turns blue and everything goes to crap.
Shut down software, unplug and plug, green light in seconds, 15-17 satellites, stable position.
So u-center seems like it doesn't really work, except that before I connected with it, I was getting nowhere.
Replies
Dale,
Your post is not easy to follow, but I understand that you had some mixed results with the NEO M8N you bought from GoodLuckSell and ucenter. I want to reply to your post because we also have two NEO M8N units from GoodLuckSell.
We have no problems connecting and communicating with those units directly with u-center or via the Mission Planner passthrough function. We found that both units acquire satellites quickly when they are in their default mode when connected directly to u-center. However, if you load the 3DR code, u-center will not show any satellites. That is because the 3DR code suppresses the NMEA message format. The GPS is actually still working fine, though, results are not being displayed because of NMEA message suppression via the 3DR code.
u-center works fine. An odd thing we did find is that contrary to the UBLOX documentation, we could not get the M8N to save the 3DR file to its nonvolatile memory. However, it appeared that the PixHawk was configuring the M8N on its own at power up, i.e., setting the baud rate to 38,000 and suppressing the NMEA message structure. So you do not need to burn 3DR code into the M8N.
The bad news: Both M8N units from GoodLuckSell appear to have a compass offset issue. They both appear to be about 30 degrees off when setting up AHRS and Compass orientation for the PixHawk. We are trying to contact GoodLuckSell about that issue right now. Please let us now if you run into the same issue.
Jim
Hi Jim & Dale,
I also bought a Pixhawk + M8N kit from GoodLuckBuy (actually GoodLuckSell on eBay) and received it a couple of weeks ago.
I only had time to put it together this past weekend and I'm having similar issues with the GPS. My main issue right now is that if I plug the 4pin cable on the I2C port the Pixhawk won't boot and I get this error on QGroundControl: "PREFLIGHT FAIL: MAG #0 UNCALIBRATED". If I unplug the I2C cable and only keep the GPS cable connected, the Pixhawk boots normally (with the blue light), the GPS gets a fix (blue light blinking on GPS) and QGroundControl reports a 3D fix with 8 sats but the Pixhawk won't acknowledge the GPS lock and LED will remain blue.
I tried doing the passthrough mode to connect uBlox u-center but it doesn't work either since the Pixhawk won't boot with the two cables connected and u-center can't communicate with the GPS if only one cable is connected.
I'm thinking there's something wrong with the MAG on my units, not sure if it's a configuration issue or a hardware issue. My only options right now are contacting GoodLuckSell and ask for a replacement or try to get one of those DT13 to FTDI cables to try to connect the GPS directly to u-connect and try to mess with the config.
What would you recommend? are the units supposed to work out of the box or is there something I need to configure on the GPS first?
I would really appreciate any help or suggestion.
- Juan
Juan,
I don't know why this would make a difference, but I got some odd behavior when I plugged mine into a different I2C port from what the original LEA6 was plugged into. Could be unrelated by it might be worth a shot to test it on different ports.
I was on the verge of getting an FTDI cable when mine miraculously started working. The problem is, I don't know exactly what I did to make it work. I was frustrated and trying one thing after another, not keeping track.
Dale
Thanks so much for your reply Dale.
I was plugging the GPS directly into the I2C port on the Pixhawk. I tried your suggestion and connected the I2C extension module and tried the GPS on different ports, but nothing worked. I contacted GoodLuckSell on eBay and they asked me to upload a video of the problem to see if their technicians could help.
I have uploaded the video but it's now Saturday in China so I will have to wait until Monday to hear back from them.
Have you flown in Loiter Mode yet?
Jim
Yes, flew mostly in loiter mode, to test the M8N. It seemed drifty at times, very stable other times. In one test, I had it visually lined up with a tall light pole, the kind you have at baseball diamonds. It stayed perfectly lined up for nearly a minute, then I increased altitude slowly. It stayed lined up until about 10 meters high, then started drifting a little. Also, I tried staying a few inches off the ground. It would stay for a while, then start slowly drifting down or up.
So, not perfectly stable, but I felt pretty confident in it. I laid a stick at the takeoff point, and then did an RTL after each outing. It landed within a meter of the stick each time.
I should add that this was at abut 98F ambient temperature, with 120-122F barometer temperature, and probably a 5-7kt wind.
Thanks Dale,
Your drift is problem due to typical GPS inaccuracy. I am having a problem getting my vehicle to lock. Thanks for the feedback!
Jim
Jim,
I flew my UAV today with the M8N for the first time, and it did really well. I was getting 16 to 20 satellites, and an HDOP from 1.05 to 1.25, with an average of 1.15. No problems with the compass as far as I can tell.
The only thing that worries me is the log files show at least one data dropout per flight from the barometer or the M8N, but these didn't affect flying at all. I never saw any erratic or uncontrolled movements.
So it seems like it was just the initial setup and u-center that were giving me problems. Honestly, I monkeyed around with u-center, and was clicking on things, and I think I just accidentally turned something on that made it work. Except I never got it to give anything but rudimentary info in u-center, and it kept drifting all over the world.
Anyway, it's working in the field now, so I'm happy with that.
Dale