Help! About the DPTH message

Hi, I have a question about onboard logs. My firmware version is fmu v3 4.2.3.
I cannot find the DPTH message in my onboard log. I tried to export POS and RFND messages and merge their content together. But then I saw another problem. The amount of data of POS and RFND is inconsistent. For example, the total amount of data, the POS message is recorded 3-5 times more than the RFND message.
Is the recording frequency of POS message synchronized with the acquisition frequency of sonar? My sonar acquisition frequency is 15HZ, but through RFND and POS messages, they record 49-51 times per second, which is a very large amount of data. Is my understanding correct or may there be a problem with my Settings?

Hi @Zenos,

The DPTH message was added to help get the timing consistent between the rangefinder (aka sonar) and the vehicle’s position. The message should appear if the vehicle is a boat and the RNGFND1_ORIENT is set to 25 (Downwards).

Hi,@ rmackay9Thank you very much for your answer.
I added the entry on the onboard log. The frame of the vehicle shown here is 2, the boat. The direction of the rangefinder (sonar) is 25, down.
If I can’t get DPTH messages, is it the right way to combine POS and RNFD messages? I don’t understand why there is a slight difference in the amount of data recorded by the two messages.


Any chance you could post an onboard log?

0000006.BIN (768.6 KB)
@rmackay9 Because of the file size, I uploaded a small log, and here you can see the data recorded by the sonar, although it’s not accurate. In this log, the POS data is recorded the same number of times as the sonar data.
Thank you very much!


Is this is a modified version of AP? RNGFND1_TYPE = 88 but this isn’t a valid rangefinder type. You mentioned the vehicle was running, “fmu v3 4.2.3” so this surprises me.

So my guess is there’s an issue in the custom driver. Maybe it isn’t properly implementing “has_data())” or “last_reading_ms()”.

Yes, this is a modified version of AP. I’m sorry I didn’t make myself clear.
I used a new sonar and added the appropriate driver to the firmware. I’ll review the code later and test it again.
Is the POS message recording frequency based on the sonar recording frequency?
Thank you very much for your help!


The POS message is output independently of the GPS and rangefinder readings…

I understand now. Thank you very much for your help. Have a nice day!

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