# imu_apps seems to be publishing in bursts

Source: https://forum.modalai.com/topic/2570/imu_apps-seems-to-be-publishing-in-bursts
Category: VOXL 2 and VOXL 2 Mini (https://forum.modalai.com/category/26/voxl-2-and-voxl-2-mini)
Tags: voxl-2
Posted: 2023-08-16 02:30:17 UTC by tanguy sagere
Replies: 4 · Views: 1212

## tanguy sagere · 2023-08-16 02:30:17 UTC

Hi! I'm working with a ModalAI Sentinel right now equipped with the VOXL2, and I've noticed after running a few test flights that the recorded imu_apps data is very patchy, with bursts of messages followed by entire seconds of silence. This puts alot of stress on my VIO. Am I missing something or is this a known issue, and if so how do I fix it?

my voxl-imu-server.conf params are the default.

Thank you in advance!

## Reply by Moderator (ModalAI staff) · 2023-08-21 18:36:00 UTC

Hi Tanguy,

That sounds like the CPU is being overloaded. Which version of SDK are you running (```voxl-version```) and can you show the output of ```voxl-inspect-cpu``` when you are seeing this issue?

## Reply by tanguy sagere · 2023-08-30 02:02:49 UTC (in reply to Moderator)

@Moderator Hi! I'm using :

```
system-image: 1.5.5-M0054-14.1a-perf
kernel:       #1 SMP PREEMPT Fri Mar 24 00:48:55 UTC 2023 4.19.125
------------------------------------------------------------------------------
hw version:   M0054
------------------------------------------------------------------------------
voxl-suite:   0.9.5
------------------------------------------------------------------------------
Packages:
Repo:  http://voxl-packages.modalai.com/ ./dists/qrb5165/sdk-0.9/binary-arm64/
Last Updated: 2023-08-24 23:20:47
```
When experiencing the message dropout, this is the output of `voxl-inspect-cpu` :

![a9b4fe28-cae8-4f66-ac67-5047903ab286-image.png](https://forum.modalai.com/assets/uploads/files/1693360723763-a9b4fe28-cae8-4f66-ac67-5047903ab286-image.png) 

![6a315d96-0bc8-4880-b96f-ea02ba72abaf-image.png](https://forum.modalai.com/assets/uploads/files/1693360962743-6a315d96-0bc8-4880-b96f-ea02ba72abaf-image.png)

## Reply by tanguy sagere · 2023-08-30 22:34:19 UTC

I've solved the problem by setting the `voxl-imu-server.conf` to

```
"imu0_enable":  true,
"imu0_sample_rate_hz":  200,
"imu0_lp_cutoff_freq_hz":      92,
"imu0_rotate_common_frame":     true,
"imu0_fifo_poll_rate_hz":       200,
...
```
Tested on 2 different VOXL2 boards, this reduces the number of lost messages sequences from 60% to <0.5% of all messages. Information on why this is the case would be interesting, as it is stated [here](https://docs.modalai.com/voxl-imu-server-0_9/) that the default config is optimized for VIO.

## Reply by tom (ModalAI staff) · 2023-08-31 00:01:08 UTC (in reply to tanguy sagere)

@tanguy-sagere I wonder if you upgrade to SDK 1.0 if the issue resolves itself