I've spent a few flights trying out the "GPS Hold" feature on the Arducopter, and have some questions.
(This is the FahPah kit, with the MTK GPS and untouched RC2 software.)
The ship is rock-solid in Stable mode. No problems; like the most docile helicopter ever.
I make sure the MTK has a Solid-Blue-LED lock before liftoff.
When I engage the GPS Hold mode (via my Tx), I see the RED Led on the board illuminate. Then it gets weird.
The ship might start to descend quickly, or lift off, or translate to the side.
I can 'fight' it with the control sticks to hold it in the origin position, but it requires constant input. If I let go, it wants to dart off to the side.
Also, the altitude control is very lethargic. If the ship starts descending, I have to give almost full UP throttle to get it to stop descending, rebound, and avoid the earth.
I have never successfully had it hold in one position.. there is always a strong bias or unexpected behavior that needs intervention.
How are others doing with this? Could I have something connected wrong?
One other odd bit: The RED Arduino LED (GPS lock) does not track the Blue LED on the GPS directly. I have to engage GPS Hold mode to see the RED LED reflect the GPS status. Normal?
Am I the only one trying Hold mode? :)
I've used GPS Hold a bit. I also have the Magnetometer. I would describe the operation as being less precise that I can control it myself. I have seen it jump around a bit; but I haven't had to do a great deal of intervention. I've seen it perform as advertised, with an accuracy of about 3-5 meters. Altitude accuracy tends to be about 1-2 meters.
"One other odd bit: The RED Arduino LED (GPS lock) does not track the Blue LED on the GPS directly. I have to engage GPS Hold mode to see the RED LED reflect the GPS status. Normal?"
I have seen this as well.
Different from you, mine has been holding position as advertised. I am disappointed with the accuracy of the position hold, and would like to find a way to improve it. I would like to see the center of the craft stay in a 1-1.5 meter box. Maybe my expectations are too high.
I would be thrilled with 3-5 meters of hold. I suspect something in my system isn't working correctly, but I'm not sure what it might be. The manual control is flawless, and the GPS is locked and received by Ardu.
I'm not getting anything close to 5 meters, and haven't let it "run far away" to see if it eventually stops or comes back. I'll get to a field today with more meters of airspace and see how far it wants to run before it decides to "hold". Altitude accuracy is worse than 10m.
It's certainly making a mode change, because the feel of both stick is very different. It just wants to 'pull' in some random direction, like there's a Trim problem.
Do you frequently have to take it Out/In GPS hold to reset the origin?
did you tune your GPS PID values?
did you set the correct geo correction factor?
did you set the correct declination for your flight area?
Doh! Really? I did not know that.
It does make sense, but I figured I would just hold Yaw manually and let it stabilize altitude and position. Hmm..
Roger that. I'll get one on order. Is there a strong preference between the DIY and Sparkfun+VoltageAdapter combo?
Might be good to put that requirement on the wiki next to the GPS Hold instructions.
Or maybe I'm just denser than the average DIY'er. :) Not the first time.
Thanks for the help.
Yes, we will update the wiki! You're actually not the first person to make that mistake.
As for DIY vs SParkfun mag. Either works but the thing I like about the DIY Drones one is that it can be mounted directly onto the Oilpan and also it works at either 5V or 3.3V (if you set the jumper correctly) so no need for a level shifter. Instructions for both are on the wiki.