Ezra Harris

Tag: Tech

  • Circumventing Safety Features

    I recently encountered an interesting problem when configuring all three drones simultaneously with the Skybrush drone management software.

    I would power up all three drones and connect them to the network I configured for them. All three would appear on my laptop. After double-checking that they were actively connected, I manually rebooted each one and confirmed the connection using the Skybrush software.

    With propellers removed, pre-arm checks approved. I would go and arm each drone.

    “Arming” is the last step before takeoff for a drone. “Pre-Arm” ensures all safety checks (foreshadowing) are completed but does not start up motors. Arming, on the other hand, starts the motors at a low rpm and listens for control inputs (i.e., throttle up) for takeoff. It disarms if no input is provided within 10 seconds of the motors spinning.

    But here’s where the problem occurred. Only one drone would go into arming mode, while the other two reported an “unknown” error and blinked red.

    After some research and trial and error, I discovered that the drone reported an “RC Not Found” error to the ground station.

    Now, that’s strange; it should be configured to ignore whether or not it had an RC connection for Pre-Flight. I went into QGroundControl and manually configured it to ignore pre-flight checks for the RC. After a quick reboot, I tried again.

    Still, no luck, except the behavior changed slightly. After the blinking red error, I tried arming the drones again… and they all spun up! But Skybrush still showed them as reporting an error. This is not ideal for my case, but as the classic saying goes, a different error is still in progress.

    After more research, I found a forum post with someone asking a similar question and a super helpful user linking to a page about configuring ArduPilot with autonomous flight software like SkyBrush.

    It ended up being two parameters that affected my problem.

    • FS_THR_ENABLE – Allow arming without checking for RC
    • ARMING_CHECK – Disable RC failsafe for pre-arm checks

    Setting those two and a quick reboot resulted in all three drones being able to go into pre-arm, then arming mode, and ready for takeoff. The corrected values are:

    FS_THR_ENABLE0
    ARMING_CHECK1048510

    The longer string for ARMING_CHECK signifies which failsafe options to disable; Arducopter gives you 19 total options for failsafe, from Compass to Battery Levels. A complete list is provided here.

    And finally, here’s a quick reference list I had ChatGPT create based on the parameter’s instructions:

    Bit Check Value Description
    0 All 1 Enables all checks
    1 Barometer 2 Ensures the barometer is functioning correctly
    2 Compass 4 Verifies compass calibration
    3 GPS lock 8 Requires a valid GPS lock before arming
    4 INS 16 Checks Inertial Navigation System (IMU) health
    5 Parameters 32 Confirms parameters are set correctly
    6 RC Channels 64 Ensures RC signal is valid
    7 Board voltage 128 Monitors voltage levels of the flight controller
    8 Battery Level 256 Verifies battery level is sufficient
    10 Logging Available 1024 Checks if logging is available
    11 Hardware safety switch 2048 Requires safety switch to be engaged
    12 GPS Configuration 4096 Verifies GPS is configured correctly
    13 System 8192 Checks system-level health
    14 Mission 16384 Ensures a valid mission is loaded
    15 Rangefinder 32768 Checks rangefinder sensors
    16 Camera 65536 Verifies camera is functioning correctly
    17 AuxAuth 131072 Checks auxiliary authorization systems
    18 VisualOdometry 262144 Monitors visual odometry sensor health
    19 FFT 524288 Verifies Fast Fourier Transform data availability

  • Drone Light Show (Part 3) – Build Goes Sideways

    Drone Light Show (Part 3) – Build Goes Sideways

    For the past few weeks, I’ve been working on getting a drone ready for takeoff and, ultimately, for formation in a light show. Since the last blog post on unboxing, I soldered the battery module onto the drone’s PDB (Power Distribution Board) with some success.

    I access the flight controller using software called QGroundControl, which has all the necessary tools for setting up and pre-planning flight routes with the Drone’s GPS. I utilized a mixed connection of USB and Wi-Fi, the Wi-Fi setup was relatively easy. I only had to change one of the drone’s parameters to instruct it how to handle the Wi-Fi connection to Ground Control properly.

    After initial setup, I was able to calibrate all of the sensors related to positioning and orientation. (Useful documentation for specific details) Next was to attach props and arm motors for takeoff. Once prepped and the battery connected, we started a slow takeoff to see the responsiveness (or, in this case, lack of responsiveness)

    Unfortunately for me, the takeoff did not exactly go “up” but rather sideways. When pushing the throttle stick, the drone would start to lean backward and or start rotating when meant to fly straight up. After a lot of trial and error, I ended up installing the latest firmware for the board we’re using. But instead of the ArduPilot firmware platform I tried the Pixhawk firmware. This shouldn’t make a ton of difference, but it had a lot more options for setup and specific configurations related to the frame we’re using instead of the generic frame I selected before.

    With flashing new firmware, it requires me to setup all of the compass and calibrations done before. One of the hurdles of calibrations was an error being thrown when we had the drone in the forward position. It would throw a generic “Test Failed”  That was fixed with a simple parameter edit (parameters, in this case, are the manual settings for each part of the drone) that would change the primary sensor for all movement to the HolyBro RTK, instead of the flight controller. Which has a basic compass and accelerometer sensors.

    Another small stumbling block was referencing a guide I had used before, which SkyBrush provides in their docs. Specifically for basic parameter setup, you need to make sure the Drone is using the RTK onboard for primary 3D sensing (basic tilt, pan, etc.) When referencing that guide, it had specific settings to change. I later figured out that PixHawk and Ardupilot each have their own parameters, and they do not carry across names. Skybrush provides firmware that is based on ArduPilot. Some are similar, but ArduPilot had a lot more advanced options; it was a stumbling block but not a huge deal as I was able to find the substitutes for PixHawk.

    PixHawk Parameters list | docs.px4.io |
    Ardupilot Parameters list | ardupilot.org |

    After reviewing a couple of examples and online forums, I realized that my motor setup was all wrong. I had both the motors spinning in the wrong directions and the motor frame setup.

    For example, this is what I believe I initially incorrectly set it up as and how it’s supposed to be laid out:

    Correct layout
    Incorrect layout

    The incorrect layout had three motors that were going CCW, which I found out when rearranging the motors as the wires were flipped. (This inverts the spin direction of the motor.) Thus, there were essentially three CCW spinning props. This caused the drone to start spinning or try to flip on takeoff. Ardupilot tried to compensate for orientation, and it ended up being a mess.

    After realizing this issue and fixing it, a quick takeoff showed that it was, in fact, the issue.

    First successful takeoff

    The day after, I reflashed Skybrush firmware and configured all of the recommended settings, and it took off as expected, showing that the motor orientation was, in fact, the main problem. The next step is to autotune and figure out what behavior changes are made in different flight modes.

    First field test

    This post includes the logos of Ardupilot and QGroundControl, which are the trademarks and property of their respective owners. I do not own any rights to these logos, and their use in this post is solely for informational and illustrative purposes. The inclusion of these logos does not imply any affiliation, sponsorship, endorsement, or approval by the respective companies. All trademarks and copyrights remain the property of their respective owners.

  • Drone Light Show (Part 2) – Hardware

    Drone Light Show (Part 2) – Hardware

    Yesterday, I got to unbox the first drone hardware; since my last post, I picked out a build based on Stan Humphries’s video “How I Build Custom Light Show Drones…” the build consists of mostly HolyBro components, while not being cheap they offered a reliable and well-documented parts compared to the competitors or parts I would have gotten cheaper off AliExpress.

    The setup for the first drone is more expensive than what you would want for an entire fleet of 100+ drones. However, it is a good testing platform for getting hands-on with the Skybrush suite.

    H-RTK F9P GNSS Series

    Pixhawk 6c

    S500 V2 Kits

    5000mAh 4S 60C Lipo

    Wifi Module (3DR)

    *Many more components contributed to the build, but I won’t include the full list here. Once I’ve got a better idea of a scalable drone build, I’ll share the BoM.

    This was my first time unboxing, so I couldn’t fully assemble every component, but it gave me a good idea of what would be required for the building process. It also shocked me how large the batteries would be and how cheap they were for their capacity. I loosely hand-assembled the drone development kit with the onboard RTK module and double-checked the correct connectors that came for wiring.

    A loose hand-tightened assembly of the drone frame.

    At first glance, it seems that there will be minimal soldering work: replacing the XT90 with an XT60, soldering the battery power module to the PDB (the drone’s built-in power distribution PCB), and Soldering the LEDs to the BEC (Battery Eliminator Circuit that regulates the voltage to a lower amount for powering LEDs).

    That’s my update! I’ll post minor updates on Discord or new information I find helpful for reference.

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  • Meta Front-End Developer Course – Week ONE

    Meta Front-End Developer Course – Week ONE

    At the beginning of July, I started a course on front-end web development taught by the Meta (Facebook) team on Coursera.

    It goes through 9 mini-courses in which it teaches you, from the introduction to how things on the Internet work to preparing for a coding interview over six months. I so far have completed the first 18-hour course and am working my way through Programming with Javascript (a 42-hour course)

    By the end, you earn a certificate from Meta, which covers the most popular web development (including the library React, which Meta developed for Javascript)

    The first course (Introduction to Front-End Development) introduced the core fundamentals of the Internet, how a server transfers info to a web browser, the most used languages, and basic HTML and CSS. It also discussed what to expect when beginning a programming career. It briefly covered how to incorporate libraries, what a Javascript framework is, how you’ll use it, etc.

    Compared to CodeCademy, it seems to be much more focused on what you should expect and prioritize what you would use in the real world. There is a lot more “in the field” of practical applications than the abstract way of teaching that Codecademy felt like, which focused on getting everything explained at once, instead of the way Meta prioritized the very basics and briefly introduced more complex topics that would be explained later when they’re needed.

    The course formatting usually goes like this:

    • Intro video to a concept (with examples of real-world use cases it can be used for)
    • a follow-up, more in-depth reading section (for example, an intro video to Javascript Arithmetic would be followed up with a reading section with every symbol variation and their use cases.)
    • In the next exercise, you will use the examples you previously learned in several specific case code snippets. (If you were learning how to use Arithmetic symbols, it would have you create a couple of different variations of equations based on what you learned before.)
    • Then, you have either a practice quiz or a quiz that reviews all the topics learned before, giving you examples of code snippets and asking you how they will be outputted.

    Module one of the second course (Programming with JavaScript) has taught me basic Javascript, such as for and while loops, fundamental variable assignment, arithmetic in Javascript, and if / else statements.

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