Frequently Asked Questions

This section provides answers to frequently asked questions about your release. Use it as the first step in troubleshooting problems.

Issues with Hardware Components

When I run my application that uses a ZED Camera I get the following error:

engine/alice/backend/modules.cpp@74: dlopen failed: cannot open shared object file: No such file or directory

The libusb-dev library is needed. Install libusb-dev and all other required dependencies on the robot with the following command:

bob@desktop:~/isaac$ ./engine/build/scripts/ -h <Jetson_IP>

Where <Jetson_IP> is the IP address of the robot.

I am running my app on Kaya. Everything runs fine. But the robot isn’t moving with the joystick.

Make sure you press the “deadman switch” L1 on the joystick while using the direction knobs. Pressing L1 is required so that unwanted motion is prevented.

When I run my application that uses a BMI160 IMU I get the following error:

I2C Error: Device or resource busy (errno 16)

The kernel module nvs_bmi160 is using the I2C resource needed by the application. Unload the module with the command sudo rmmod nvs_bmi160. You can also run the script, which prevents nvs_bmi160 from loading.

bob@desktop:~/isaac$ ./engine/build/scripts/ -h <Jetson_IP>

Issues with the Visualization and WebSight

I don’t see images in Sight. Or the images are blank. Or the labels displayed are red.

In Sight, under Channels, make sure the checkboxes corresponding to your channels are enabled. Similarly, if the labels under the windows show up in red, it means the stream is not enabled.

Unable to see the Sight webpage after opening :samp:`http://localhost:3000` in a browser

Make sure an application is running on your desktop. If you are running the application on the robot you have to use the robot IP address.

If the error “Failed to start Webserver!” error message appears in the logs, the port may not have been released by a previous application.

Determine the application which is using the port with the following command:

lsof -i TCP:3000

Kill the application with the following command:

killall -9 <app name>

Sight visualization is very slow

When network bandwidth is insufficient, channels displayed in Sight may show with latency or at very low framerates. Do the following to :

  • In Sight, under Channels, uncheck all unnecessary channels.
  • Verify Wi-Fi antennas and cables connecting to the PCIe Wi-Fi card.
  • Change the power mode of the Wi-Fi adapter by checking the file.
cat /etc/NetworkManager/conf.d/default-wifi-powersave-on.conf
wifi.powersave = 2

Should be moved to

wifi.powersave = 3
  • Try a wired connection to rule out Wi-Fi bandwidth issues.

Other Issues

**What is the easiest way to generate a capnp id for a new message? The Bazel error message says to
use capnpc -i, but that does not seem to work.**

If you build without a capnp ID, a new ID is generated and printed with the error message. You can then use this ID for your new message.

When running an application that requires TensorFlow, I get the following error: PANIC engine/core/buffers/algorithm_cuda.cpp@55: Could not copy memory. Error: 35

To resolve this error, install CUDA 10 using the instructions at NVIDIA CUDA Installation Guide for Linux.

How to Add a New External Dependency

Your packages or components might require external dependencies not yet available in Isaac. The right strategy for integrating a new external dependency can vary case by case. There are several examples in the folder third_party. This tutorial explains how to add the zlib library.

First, find a reliable source for your dependency. In the case of zlib we get it from the official zlib webpage at To avoid unexpected problems in your codebase when the external dependency is updated you should fix a specific version of the library. For this tutorial we choose the version 1.2.11.

Second, add the dependency to our WORKSPACE file using the Bazel rule new_http_archive as shown in the following code:

    name = "zlib",
    build_file = clean_dep("//zlib.BUILD"),
    sha256 = "c3e5e9...cb1a1",
    strip_prefix = "zlib-1.2.11",
    url = "",

The main difference between new_http_archive and http_archive is that new_http_archive is for dependencies that are not accompanied by a BUILD file, and http_archive is for dependencies which are accompanied by a BUILD file.

See the official Bazel documentation for information on the various parameters for new_http_archive and documentation of all Bazel rules.

Importing the external dependencies as an archive is generally preferred over using the rules new_git_repository or git_repository, which import git repositories, because archives are smaller and have less overhead than git repositories.

Third, for the purposes of this tutorial, assume that you have to write a BUILD file for the new external dependency (This may not always be required.) In the case of zlib this is quite straight-forward:

  name = "zlib",
  srcs = glob(["*.c", "*.h"], exclude="zlib.h"),
  hdrs = ["zlib.h"],
  copts = [
  includes = ["."],

This BUILD file defines a single C++ library named zlib, using the Bazel rule cc_library. Our library includes all C source and header files from zlib and compiles them into a single library. The only external header file is zlib.h which is excluded from the sources so that the same file does not appear as a source and a header.

In general, srcs is used for files internal to the library and can be used for both source and header files. hdrs is used for publicly facing header files which are required in applications that use the library.

A couple of compiler flags are also required, added using the copts option to avoid compiler warnings which are treated as errors due to use of the -Wall option by the Isaac compilation tool.

The new library is ready for use as a dependency in one of your libraries or binaries, similar to the following example:

  name = "foo",
  srcs = ["foo.cpp"]
  hdrs = ["foo.hpp"],
  deps = ["@zlib"]

Every external dependency is creating its namespace with the same name as the one used for the new_http_archive or corresponding rule. In this case the name of both the dependency and the library is zlib and thus the shortcut @zlib can be used to refer to the library. If there were a second library foo inside the same archive, the explicit form @zlib//:foo would be needed to reference it.

How To Analyze a Crash using Minidump

In the case of a crash, Isaac SDK applications attempt to collect information with breakpad. This information is written into a minidump file in binary format. This section explains how to extract human-readable information from minidump files.

Prepare the Minidump Toolkit

Prepare the minidump toolkit in the /tmp/minidump/ with the following command:

bob@desktop:~/isaac$ ./engine/build/scripts/

Prepare Symbols

Prepare symbols before testing applications by passing the argument ‘-s’ when deploying applications as shown in the following command:

bob@desktop:~/isaac$ ./engine/build/ -s -h <IP> -d <device> -p <target>

Analyzing Minidumps

When a crash happens, Isaac application minidump file paths are reported at the console similar to the following:

Minidump written to: /tmp/28db00a1-e756-4c47-62f6a7b6-fc26c1a0.dmp

To make the minidump data human-readable, at a desktop that has symbols prepared, run the following command:

bob@desktop:~/isaac$ ./engine/build/scripts/ -h <IP> -d /tmp/28db00a1-e756-4c47-62f6a7b6-fc26c1a0.dmp

or if the minidump file is locally available, run the following command:

bob@desktop:~/isaac$ ./engine/build/scripts/ -d <minidump>

Crash information is presented at the console, and is similar to the following:

Crash address: 0x0
Process uptime: not available

Thread 11 (crashed)
 0  realsense_camera!isaac::RealsenseCamera::tick() [RealsenseCamera.cpp : 533 + 0x4]
     x0 = 0x0000000000000000    x1 = 0x0000007f962b2180
     x2 = 0x0000007fa0000080    x3 = 0x0000007f800008d0
     x4 = 0x0000000000000007    x5 = 0x00000000007e8ac8
     x6 = 0x00000000007e89f0    x7 = 0x0000000000063762
     x8 = 0x00000000000000d7    x9 = 0x001dcd6500000000
    x10 = 0x000000005c787d6b   x11 = 0x000000000f171c90
    x12 = 0x0000000000000017   x13 = 0x000000005c787d6b
    x14 = 0x00076f61bec52c49   x15 = 0x00001c2c8948c9df
    x16 = 0x0000007fa7708688   x17 = 0x0000007fa7471838
    x18 = 0x0000007fa005bdcc   x19 = 0x0000000037cc4610
    x20 = 0x0000007fa004bbb0   x21 = 0x0000007fa0248c01
    x22 = 0x0000000037cc47e0   x23 = 0x00000006556cdce8
    x24 = 0x000000000091f000   x25 = 0x0000007fa53dd330
    x26 = 0x0000000000000000   x27 = 0x0000007f962b31b0
    x28 = 0x0000000000000001    fp = 0x0000007f962b20a0
     lr = 0x0000000000459f6c    sp = 0x0000007f962b20a0
     pc = 0x0000000000459f74