timestamp latency

[alexsaso]

I am using a Lord Microstrain 3DM-GX5-25 IMU together with this driver. I have the IMU rate configured at 500 Hz, meaning I expect an imu message each 2 ms (0.002 s). This is the case for the most sequential messages, but some messages are further apart (up to 20 ms).

Does anybody know, why is this happening? I was thinking it could be following:

• some messages are dropped
• system is overloaded and the processor gets to it with some latency

Thanks,
Aleks

[versatran01]

I think point 2 might be the reason.

Have you tried this one https://github.com/ros-drivers/microstrain_mips
This supports gx5 while ours has not been tested with one.

[alexsaso]

Thank you for your answer, I will check out the other driver as well.

There is another thing that I have noticed. I store the imu messages into a bag file. When I check the sequence numbers of the messages, I noticed that out of the 4193 messages are missing (meaning sometimes the sequence is not incremented for +1 but a larger number). Does this mean that there are messages dropped and why could this happen?

[versatran01]

There could be many reasons that cause messages to drop. (maybe system is under heavy load).
If only a few dropped from 4000 msgs then I wouln't worry too much.