Ezra Harris

Category: Programming

  • 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

  • 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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