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IMU Calibration Issue
Hi Sean,
Thanks for the answer. I'm able to calibrate the IMU but the signal K value always drops to 0.9936...rad and I only see my calibration offset of the compass in OCPN. If I moove the PCB, it goes back to decent value (no way to compare to a real value) stay still for a while and the drops again. Heel and Pitch are very consistent. I've got an other BNO to swap with while waiting for the MPU9255 to arrive.

for an other project I used a compassmodul based on the Bosch BNO055.
This sensor have an internal automatic calibration routine witch seems not to be able to use in marine enviroment.
It works at home on the table but not on the boat.
The newer modules have the possibility to switch of theese calibration routine.

Kind regards

the bno055 seems to have internal routine, but I have not tried it. I don't think the routine knows the difference of the marine environment or not, and there is nothing about water around the boat that affects in. In contrast many houses have metal bars in the walls which greatly affect the field. Perhaps the boat itself has significant distortions, certainly a steel or ferro cement boat would.

shure the sensor don't know where it is.

The internal auto calibration of the BNO055 works if the sensor lies still on table but fails when on board.
The moving of the boat when underway seems to desorientate the auto calibration. If the boat is in the harbour the sensor works fine. When underway the heading swings random up to 90 degrees.
This experience made more then one user of this module.
My boat is GFK and the older sensor without automatic calibration works fine.

So it's just a hint for a possible fault.

I used the module CMPS12 witch was useless. Now there is a module CMPS14 on the market wich allows to switch off the automatic calibration. Don't test it but if I get problems with the sensor I would try to switch off the automatic routine.

Best regards


I am indeed at home at the moment without the possibility to test the accelerometer on my boat... I was able to find a place in my house where the magnetic field is not too distorted! My problem with the BNO 055 is more a random reset than a compass value that would be bad. I tried another module (I use adafruit modules which are known to be quite reliable in their fabrication). With this new module, I have the same behavior.
I received an MPU 9250 (I had ordered an mpu 9255...) and after some calibration problems due to a disturbed field, everything seems to work correctly now.
However, I have a question: Is the sensor response time slow with all sensors? If I turn the sensor quickly by 180°, it takes about 6 seconds for the display to stabilize at the right value. I could see this also in the Pypilot scope by displaying imu.heading. Is it programmed like this in pypilot to avoid sudden changes in the compass and to guarantee a good control of the steering?

Thanks again for all the information and the development of pypilot!

I am having a similar problem as Gambol originally posted to commence this thread.
I am totally new to the rasp pi and OpenPlotter so any proposed solutions I respectfully request be step by step please.
I have a pi4 (4gb) and BerryGPS-IMU V4 installed as a hat. Both were purchased in the last week.
I have used the latest OpenPlotter Basic image per the website and followed all the instructions. All installs and updates went without a hitch.
I am able to get a correct GPS position on OpenCPN with an external antenna but I have to go outside my house to get it.
I am getting a barometric pressure reading and it displays on the dashboard ok

But that's all I get.
Just like Gambol, while in Pypilot (compass only) I do not get my BerryIMU discovered. It just says Auto Discover. There does not appear to be any way to configure an IMU with Pypilot that I can find at least.
I2cdectect reveals the IMU sensors addresses OK.

I purchased the BerryGPS-IMU V4 because they have a good name and the new Moitissier Hat does not appear to be on the market yet.

I appreciate any assistance to move this project forward so I can install on my boat.

Thank you

Edit: I should have added... I am not using headless mode.
Also the magnetometer being used is the LSM9DS0. It's data sheet can be found here.

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