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
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
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