bug: I2C6 Bus speed might be too high.

[JackSkellet]

Bug description

On some Navigator setups i have experienced Noise in the Depth Sensor reading.
I am not entirely sure if this is due to us using Topside supplied power or not.

Messing with the Baro_Filter range in ardupilot have to some extent managed to tame this behaviour in the past, except for a few outliers.

i took it upon myself to check the i2C speed for that bus, after changing it from 400000 to 100000 and adding the #custom comment inline, the noise seems to be mostly gone..

And adding 47ohm inline resistors to the baro SCL and SDA i got it to be even more stable.

Sometimes going max speed is not the right answer😅

Steps to reproduce

like i stated before, i am unsure if this is related to our topside powersupply or not, but you can check it yourself by plotting the live baro data before and after the change.

Primary pain point(s)

in some cases the noise can be big enough for Ardupilot to bug out in such a way that it will do 1 of 3 things.

1. start ocsilating heavily.
2. Shoot straight up to the surface, while being unable to stop unless entering manual mode.
3. same as 2 but straight down.

this can in some cases lead to destruction of equipment and or the ROV.

Additional context

Here is a Graph view after Changing the Boot config file. do note that the maximum change is +/- 0.01

And this is before. now this is taken while diving down and staying there full throttle. but the variance is high.
i will add on to this post once i get it back in the water for testing with the new setup

noise.mp4

Prerequisites

• I have checked to make sure that a similar request has not already been filed or fixed.

[github-actions]

Yo, this issue might be related to:

• bug: Navigator i2c-1 not using maximum clock speed #1802: similar Navigator I2C bus speed configuration problems (though that one was about increasing speed on i2c-1 vs decreasing speed on i2c6)

[JackSkellet]

Here is another Before image, but this time, on land not doing anything

and another After, now actually put together and waiting for pool test.

after pool test, it is still not perfect. but its way less noise than before...

Screencast_20260116_134424.webm

[JackSkellet]

after a bit more tweaking on my part. moved around on some cables by the navigator. it got better still. but it still has some jerk to it

Screencast_20260116_153148.webm