Have you measured latency (response time) of sensors?

[MiloMindbender]

Hi @kriswiner,

I setup my test robot with both a BNO055 and MPU 9250. The BNO is doing its sensor fusion internally, the 9250 is running the 6dof fusion algorithm on its internal Digital Motion Processor.

I am reading both sensors at 100hz (10ms) and graphing the roll output. The 9250 appears to lag 50-100ms behind the BNO055. Also every run seems to have a different amount of lag.

I measure this by rocking the robot back and forth and then measuring the time between peaks on the graphs from both sensors.

I didn't see anything about response time latency in your wiki pages comparing sensors. Have you ever measured this? I'm just trying to get an idea if what I am seeing is normal or if I've maybe done something wrong setting up the chips.

[kriswiner]

I don;t use the DMP, so no idea...

On Tue, Sep 11, 2018 at 4:20 PM MiloMindbender notifications@github.com wrote:

Hi @kriswiner https://github.com/kriswiner,

I setup my test robot with both a BNO055 and MPU 9250. The BNO is doing its sensor fusion internally, the 9250 is running the 6dof fusion algorithm on its internal Digital Motion Processor.

I am reading both sensors at 100hz (10ms) and graphing the roll output. The 9250 appears to lag 50-100ms behind the BNO055. Also every run seems to have a different amount of lag.

I measure this by rocking the robot back and forth and then measuring the time between peaks on the graphs from both sensors.

I didn't see anything about response time latency in your wiki pages comparing sensors. Have you ever measured this? I'm just trying to get an idea if what I am seeing is normal or if I've maybe done something wrong setting up the chips.

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/kriswiner/MPU9250/issues/307, or mute the thread https://github.com/notifications/unsubscribe-auth/AGY1qjPn3l46UgNTTvhr1HRQhuJ82pA0ks5uaEU5gaJpZM4WkYpm .

[MiloMindbender]

When you tested different sensors with your usual methods did you see any difference in lag?

I will test raw data today, if you have any data, even for raw sensors, it helps me make sure I'm not messing up something.

Thanks!

[kriswiner]

We never tested for latency. But we use the MPU9250 for robot navigation (rolling and flying) so I don;t think we would be able to do this well with 100 ms latency. I suspect this is an artifact of the DMP, which heavily filters the 6 DoF sensor data to get euler angles, likely introducing the delay you are seeing.

Why not try the 6DoF or 9 DoF Madgwick filter and test latency there, it is likely to be much less of you run your sample rates at 1 kHz and use a fast enough MCU to get fusion rates at a few kHz.

On Wed, Sep 12, 2018 at 11:59 AM MiloMindbender notifications@github.com wrote:

When you tested different sensors with your usual methods did you see any difference in lag?

I will test raw data today, if you have any data, even for raw sensors, it helps me make sure I'm not messing up something.

Thanks!

— You are receiving this because you were mentioned. Reply to this email directly, view it on GitHub https://github.com/kriswiner/MPU9250/issues/307#issuecomment-420760726, or mute the thread https://github.com/notifications/unsubscribe-auth/AGY1qrm51lxOsNE2P4LDflz_Ev42ve3Fks5uaVmZgaJpZM4WkYpm .

[MiloMindbender]

Thanks! I'm thinking the most likely cause of my problem is data getting delayed in the 9250 FIFO maybe due to incorrect configuration. Since the BNO055 doesn't have one, no delay.