250mm Revo with GPS - is this a lost cause ?
« on: May 14, 2017, 05:12:23 pm »
Hi all,

I have built a 250mm quad based on the QMR250 frame with the Revo board. I have also got a GPS connected to it.

For the life of me I simply cannot get the Magnetometer calibrated. I must have got through the 6 position calibration like 20 times in different locations and I am still not able to get the GPS mode to work due to the magneto calibration.

So, I am about ready to give up. I think since the PDB is very close to the Revo board it's causing the revo to screw up the magnetometer calibration.

And after reading quite a few frustrated posts in the forum, it looks like this is a waste of time.

So please, has anyone successfully built a 250mm revolution board with GPS capability ?

DroneSaif

Mateusz

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Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #1 on: May 14, 2017, 05:55:13 pm »
Yes, but GPS has built-in magnetometer and is mounted on 14cm mast. Magnetometer on Revo won't work unless you mount flight-controller ~14cm above your copter. You need built-in magnetometer to align (find orientation) of the external magnetometer, then you switch to use AuxOnly (instead of Both) and you can fly. Magnetometer is the only sensor that can give algorithm heading information. Even DJI phantoms don't have magnetometer at COG, they have these sensors in landing pads.

It will not work then way you assumed.

Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #2 on: May 14, 2017, 06:46:46 pm »
It is when you are flying and the motors are drawing high power that the bad mag fields appear and mess things up.  The mag problems that you have when trying to make a small quad don't usually affect calibration.  You can still do calibration.

Three (maybe more) things generally make the calibration fail:
- Once you start, it is calibrating the whole time, not just when the progress bar is moving.  This means that you must be careful not to set the quad down or walk with it into a bad mag field area while doing the calibrations.  You should be outside, away from metal, in an area where you might fly it, and off the ground and never sitting on a car.
- Mag calibration works best via OpLink RF, not USB
- Having a magnet anywhere around the mag sensor (hatch hold down, lipo alarm speaker, etc) is a problem.

utoedter

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Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #3 on: May 14, 2017, 07:23:53 pm »
I did the same learning process on my Eachine 250 racer. Finally i got it working, mine works fine with a Ublox GPS for Naza flight controller.  That one has a magnetometer and includes the compass data in the GPS data stream. To use it with the Revo, you have to cut off the plug and replace it with a JHST-4 plug. The wiring and configuration  is explained in the wiki.  Tried it also with revo built in mag, but thats too close to disturbing magnetical fields. Now i can use all flight modes in combination with INS13 Navigation.

Udo


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« Last Edit: May 15, 2017, 09:08:47 pm by utoedter »

Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #4 on: May 14, 2017, 07:46:39 pm »
Yes, but GPS has built-in magnetometer and is mounted on 14cm mast. Magnetometer on Revo won't work unless you mount flight-controller ~14cm above your copter. You need built-in magnetometer to align (find orientation) of the external magnetometer, then you switch to use AuxOnly (instead of Both) and you can fly. Magnetometer is the only sensor that can give algorithm heading information. Even DJI phantoms don't have magnetometer at COG, they have these sensors in landing pads.

It will not work then way you assumed.

Well my AuxMag does not seem to exist, despite my GPS being the Ublox M8N with compass. I wiuld ahve to solve that mystery first I suppose.


Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #5 on: May 14, 2017, 07:53:08 pm »
It is when you are flying and the motors are drawing high power that the bad mag fields appear and mess things up.  The mag problems that you have when trying to make a small quad don't usually affect calibration.  You can still do calibration.



Well, the GCS says that the magnetometer is calibrated. I save it, and reboot the quad. And the "MAG" alert is RED and the onboard magAlarm is saying 70+% error.




Three (maybe more) things generally make the calibration fail:
- Once you start, it is calibrating the whole time, not just when the progress bar is moving.  This means that you must be careful not to set the quad down or walk with it into a bad mag field area while doing the calibrations.  You should be outside, away from metal, in an area where you might fly it, and off the ground and never sitting on a car.
- Mag calibration works best via OpLink RF, not USB
- Having a magnet anywhere around the mag sensor (hatch hold down, lipo alarm speaker, etc) is a problem.

I am using the OpLink to do the calibration.
I was outside for maybe around 10 of these attempts.


Will try again outside in an open area. But then, it kinda defeats the purpose, as it's not where I intended to use the drone. but at least maybe I will get the mag alarm to tun green.

f5soh

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Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #6 on: May 14, 2017, 07:59:51 pm »
Quote
Well my AuxMag does not seem to exist, despite my GPS being the Ublox M8N with compass. I wiuld ahve to solve that mystery first I suppose.

No mystery i think.

Did you connect physically the I2C lines for Auxmag ?
https://librepilot.atlassian.net/wiki/display/LPDOC/GPS+setup#GPSsetup-GPS+I2C

Assuming chinese put the two wires for I2C + Mag sensor and not only the "GPS+Mag" case :)

Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #7 on: May 14, 2017, 08:23:39 pm »
That's the mystery. I only have a 4 wire connector going to my flexi port.

I guess I would  have to open the GPS casing to see what this actually is.
« Last Edit: May 14, 2017, 08:51:44 pm by f5soh »

Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #8 on: May 14, 2017, 08:39:30 pm »
Ok... There are no magnetometer in this GPS module. Just a casing.

Bastards.

« Last Edit: May 14, 2017, 08:51:57 pm by f5soh »

f5soh

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Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #9 on: May 14, 2017, 08:54:30 pm »
Best choice is Naza GPS, all (position+mag) using the same connection/port.

Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #10 on: May 14, 2017, 09:08:12 pm »
Best choice is Naza GPS, all (position+mag) using the same connection/port.

So how would you configure the revo port ? as GPS or as I2C


Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #12 on: May 14, 2017, 09:14:24 pm »
I used, this aux mag sensor : https://www.aliexpress.com/item/GY-282-HMC5983-Replace-HMC5883L-High-precision-High-sensitivity-Temperature-Compensation-Triaxial-Compass-IIC-SPI-Module/32333887264.html?spm=2114.13010708.0.0.K7EBD9
In my opinion, is better than the stoc HMC5883L but with the expense of a port (flexi - ic2).
Maybe you could give it  a try if you already bought the gps without mag chip.


Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #13 on: May 14, 2017, 09:20:58 pm »
Did you take a look at the link above ?

Naza GPS:
https://librepilot.atlassian.net/wiki/display/LPDOC/GPS+setup#GPSsetup-NazaGPS

GPS+I2C:
https://librepilot.atlassian.net/wiki/display/LPDOC/GPS+setup#GPSsetup-GPS+I2C

I did, but I admit not paying attention earlier when it said Naza GPS, cos I don't have that.

Re: 250mm Revo with GPS - is this a lost cause ?
« Reply #14 on: May 14, 2017, 09:39:56 pm »
I used, this aux mag sensor : https://www.aliexpress.com/item/GY-282-HMC5983-Replace-HMC5883L-High-precision-High-sensitivity-Temperature-Compensation-Triaxial-Compass-IIC-SPI-Module/32333887264.html?spm=2114.13010708.0.0.K7EBD9
In my opinion, is better than the stoc HMC5883L but with the expense of a port (flexi - ic2).
Maybe you could give it  a try if you already bought the gps without mag chip.

I will look into this. Thanks.