RM3100 External Compass

I am using Zubaxx compasses right now and i must say that since i unloaded the other compass drivers and loaded only the UAVCAN, compasses work much better and don’t give us any more probs.

I’ll test the 3100 in the near future but i really don’t like I2C bus much.

Hopefully someone will come out with a UAVCAN F9P GPS with 3100 compass, that would probably be a really great combo.


Its been a while since you started testing the 3100. I just purchased one and its on its way. How did your testing go and are you still using it?

Has anyone tested yet? Any noticeable performance difference? Maybe in combination with F9P?

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How much work do you think it’d be to back port the RM3100 driver to 3.6? Did the internal APIs change much between 3.6 and 4.0? I’d like to use the DroTek F9P Sirius RTK GPS, but I’m reticent to jump to 4.0 alpha for an expensive copter.

We merged the support into master, it should appear soon in next 4.0 RC too.
About backporting, it should be pretty simple as the library is really simple

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Good day, ive purchase the drotek rm3100… as only on my gps I’ve an extra i2c port how i can configure it on MP?
My gps is wired on can node but ive saw that on the bottom of the can board I’ve also the spi pads… better i2c or spi?
Hoping for your advice…

ArduPilot probes the I2c bus for the 3100. You can run multiple devices in parallel on the i2c bus by using an i2c splitter or you can use one of the gps serial ports and connect only power, ground and SCL/SDA. The 3100 would not be available through the CANbus gps.

Good day, i have the mro can node… on the top of the board i have one I2C port and one 6pin pin serial port where ive attached the gps, on the bottom there are the pads but name of spi seems be different from the pinout scheme of the drotek spi pinout

Use the i2c port. Don’t worry about CAN, it’s of no use to you for the mag.

ok… but if i want use SPI what will be the difference coz i don’t like to much the i2c

I don’t think that spi will work. I2c is really not a problem with the 3100 as it cam be mounted much closer to the AP without issues. I have all of mine mounted less than 2cm from the autopilot with great results. image

Sounds good that i2c don’t have any problem with this module… i will test it soon when it will arrive. Me I’ve already active two external compasses coz already on my gps board i need only calibrate and active the third external… correct?
How’s the results during the flight?

Yes you will have to select the primary compass and calibrate. I would choose the 3100 as primary as it will be much more accurate and less prone to interference. I have the 3100 on 3 vehicles and each is very stable with no compass issues at all, much better than any compass i have used.

My gps is connected on a can node and LIS3MDL and IST8310 soldered on gps board will be automatically recognized as compass 1 and 2… the 3rd internal and external are disabled by me due too high offset

Mag numbers are allocated by the firmware but you can select “primary compass” in mission planner to either 1, 2, or 3.

You are right i forgot there is a scroll menu option for choose use primary compass…
Thank you for your help and time

Good day, finally the module arrived… ive installed it… after the calibration the parameters after the calibration is really good…

Happy everything worked out for you. It is amazing how the Hall effect is not affected by variations in the mag field nearly as much and remains stable and accurate in all conditions. I just received a couple of new units from FlyFocus and am in the process of field testing. For test purposes I am purposely mounting the mag modules in bad electromagnetic places directly on the airframe. So for results are very good, actually better than conventional mags elevated on a mast.

Happy flying

The one I’ve bought is by drotek… but ive purchase also the one by flyfocus for my drone project… the frame I’ve designed is totally in 3d, and the one of flyfocus will fit perfectly. I’ve mount it directly on the frame… low magnetic field and no compass offset too high… green parameter.
Happy fly too

What orientation are you folks mounting your modules at ?
I’ve got a pair of PNY breakout boards, and come weekend I’d love to test them.