FIRST Tech Challenge Tech Tips

Started in the 2023-2024 season, Tech Tips are a weekly segment released in the FIRST Tech Challenge Team E-mail Blast. Sometimes the Tech Tips are included in whole in the email blast, but sometimes there is more content than is reasonable in the email blast so partial content is included in the blast with the rest of the content here. Blasts are ordered on this page chronologically, with the newest content at the bottom of the page.

Just click to expand the Tech Tip you’d like to read.

Week of 09/04/2023 “Battery Charging”

The FIRST Tech Challenge Tech Tip of the week this week is all about Battery Charging. There are three robot main batteries that are legal to use in FIRST Tech Challenge, and they are all 3000mAh NiMH batteries with an attached 20A fuse. However, the manufacturers of the batteries have different battery chargers and different recommended charging settings for the batteries. When charging the TETRIX MAX 12-Volt battery, on the battery the manufacturer recommends charging at the 0.9A charge rate (the lowest setting on most selectable battery chargers) using the Global NiMH battery pack charger. The Matrix 12-Volt battery with the same form factor is recommended to be charged with the goBILDA 12V battery charger, which does not have a user-selectable charge rate switch but has a max charge rate of 1.0A. However, the REV 12-Volt Slim Battery is recommended to be charged with the REV Battery Charger using the 1.8A charge rate setting. To ensure safety, proper charging, and a long battery life, make sure you’re charging your batteries at the manufacturer’s recommended charge rates!

Week of 09/11/2023 “Updating the Robot Controller App”

This week’s Tech Tip of the week is all about updating software on your Control Hub. If you use Android Studio, did you know that you’re not supposed to use the REV Hardware Client to update the Robot Controller (RC) App? Blocks and OnBot Java programs are stored on the Robot Controller (SmartPhone or Control Hub) differently than Android Studio programs, and this has a major effect on how updates can be managed on the device. Read more about this at Updating the Robot Controller (RC) App.

Week of 09/18/2023 “Technical Update video by AJ Foster”

This week’s Tech Tip of the Week is a Video Tech Tip of the Week from AJ Foster, FIRST Tech Challenge World Championship FTA and Orlando Robotics League All-Star Volunteer. AJ gives a great synopsis on many of the key technical updates for the CENTERSTAGE presented by RTX season and some background on those changes. Watch his video on the FIRST Tech Challenge YouTube Channel here: https://youtu.be/uOcVGwdhG3E.

Week of 09/25/2023 “3D Printing Resources on FTC-Docs”

Do you wish you knew more about 3D printers, filament, and choosing and maintaining a 3D printer? This week’s Tech Tip of the Week highlights ftc-docs community contributions from FIRST Tech Challenge teams 16461 and 1002 introducing 3D printing in FIRST Tech Challenge. Once you’ve got a 3D printer, be sure to check out Computer Aided Design (CAD) also on ftc-docs to find a CAD package and start designing and printing parts for your robots!

Week of 10/02/2023 “Choosing the right Webcam and Calibration Crowd-sourcing”

When using AprilTags, choosing the right webcam can save you from having to perform your own calibration before being able to use it for obtaining AprilTag Pose information. This week’s Tech Tip of the Week explores the new Webcams for VisionPortal document that highlights several commonly used webcams that have calibration data built-in to the SDK itself. Maximum frame rates, field of view, and supported resolutions with calibration data are all covered for each of the most common webcams in FIRST Tech Challenge. Short on time? Be sure to check out the handy quick summary at the bottom of the page! Did you calibrate your own camera and determine lens intrinsics for it? Please check out this FTC-Community post to contribute to the crowd-sourcing effort for calibration data!

Week of 10/09/2023 “Hardware Connection Diagrams”

Have you ever asked, “How does that get connected?” when working with FIRST Tech Challenge control system components? This Tech Tip of the Week highlights Stefen Acepcion of FIRST Robotics Competition Team 3161 - he has graciously compiled several connection diagrams that demonstrate different ways that common components can be connected within the FIRST Tech Challenge control system. Driver Station connection diagrams (both Driver Hub and Android Smartphone configurations) and Robot Controller connection diagrams (both Control Hub and Android Smartphone configurations) can be found on ftc-docs. Stefen has contributed additional diagrams this season, including a new Advanced REV Control Hub connection diagram and a new Advanced Smartphone connection diagram. These diagrams are chock full of helpful tips, connection techniques, and information you otherwise can’t find in one place - check them out!

Week of 10/16/2023 “Battery Maintenance Tips”

This week’s Tech Tip of the Week is an extension to our first-ever Tech Tip of the Week regarding battery maintenance. Nickel-Metal Hydride (NiMH or Ni-MH) batteries, like those used in FIRST Tech Challenge, do require periodic maintenance to keep them healthy! Every day, NiMH batteries lose on average 1% of their charge capacity at normal room temperature - at colder temperatures this decline slows a bit but does not stop it. This means that every 2-3 months it’s important to recharge your batteries to keep them healthy - there is no off-season for batteries! It’s also recommended to mark your batteries with tape and a sharpie to mark (1) Your team number (never lose a battery at a competition!), (2) What year the battery was purchased, (3) Give your batteries names so you can differentiate batteries easily, and (4) optionally provide a tick mark each time the battery is recharged. NiMH batteries can generally last 200-300 recharge cycles before their internal resistance declines to the point where it’s time to replace them, and keeping track of charge cycles is an easy way to track how “used” the battery is before needing to have its internal resistance checked.

Week of 10/23/2023 “Control and Expansion Hub Tips”

This week’s Tech Tip of the Week provides useful tips when using Control and Expansion Hubs.

• The RS485 data cable ports that provide data between Control and Expansion Hubs are redundant - you can use two data cables utilizing both ports to ensure that if one cable fails communications aren’t lost.

• Encoder ports 0 and 3 are hardware-counted, but ports 1 and 2 are software-counted. This means higher counts-per-revolution encoders (like the REV Through-Bore Encoder) should be placed on Ports 0 or 3 to ensure counts aren’t missed, and lower counts-per-revolution encoders (like the goBILDA Odometry Pods or most motors) can be connected to any port.

• Servo port pairs (0,1), (2, 3), and (4,5) each share a common power supply, so if you’re using higher-current servos (like a goBILDA torque servo) directly on the Control or Expansion Hub you should only use ports (0, 2, 4) or (1, 3, 5) in order to maximize the power available to each servo. If you need to use more than 3 high-current servos per hub, consider using a REV Servo Power Module.

• Each Digital and Analog sensor connector on the Control and Expansion Hub each have 2 signal channels. Some REV sensors are only designed to be configured and used on the N or N+1 channels. Read the documentation for each sensor carefully!

• The USB 2.0 port shares the same USB bus as the internal Control Hub radio. ESD or other electrical interference that affects devices (like webcams) plugged into that port may cause a loss of communications. When using a USB webcam, use the USB 3.0 port first.

• USB C-to-C cables do not work properly with the Control Hub, only USB A-to-C cables do.

• If you’re utilizing the onboard IMU, Do not plug I2C devices into Port 0 unless absolutely necessary. Port 0 shares an I2C bus with the IMU, and misbehaving devices (or devices that don’t “play well with others”) plugged into Port 0 can cause the IMU to stop communicating.

Week of 10/30/2023 “Computer Requirements”

This week’s Tech Tip of the Week focuses on required computer hardware for FIRST programs. If you’re looking to buy a laptop and want to make sure you meet the minimum requirements for the program you’re participating in, like FIRST Tech Challenge, this tech tip is for you! There is a new Computer Requirements document on ftc-docs that provides a cross-program view of the laptop requirements for all FIRST programs. It also has examples of the different laptops and a list of the required features needed for each program. Check it out!

Week of 11/06/2023 “Driver Hub or Smartphone?”

This week’s Tech Tip of the Week briefly discusses the pros and cons of Smartphones versus the Driver Hub. Which one should you use? Are there hidden benefits or perils for using one over the other?

The REV Driver Hub is the standard FIRST Tech Challenge Driver Station hardware device. It boasts three USB-A ports for plugging in gamepads, a USB-C port used for communication and charging, a large touch screen, and an unused Ethernet port (for future-proofing). This device runs the Android operating system, maintained by REV Robotics, and uses Wi-Fi to communicate with the REV Control Hub.

Driver Hub Pros

• Driver Hub and Control Hub combo use 802.11w for communications. No approved Smartphone supports 802.11w communications.

  • 802.11w offers encryption of control packets, which prevents many Wi-Fi attacks by remote routers/devices.

• Driver Hub is a “standard” FIRST Tech Challenge Driver Station device, which provides long-term support for FIRST Tech Challenge. The average SmartPhone is deprecated within 2 years after being released, but the Driver Hub is supported as long as it’s legal to use in FIRST Tech Challenge.

• Driver Hub has a USB-C port, which allows for charging while it’s being used.

  • USB-C port allows use of external battery packs, which are necessary for sustained use of PS4 and PS5 gamepads which leech power from the Driver Station to charge their own internal batteries.

  • A single 10,000mAh External battery pack allows Control Hub to be used non-stop over the course of an entire day.

• Driver Hub has 3 USB-A ports, so no external USB hubs and additional cables are required for using multiple USB gamepads. This makes the Driver Hub very compact and easy to manage.

Driver Hub Cons

• Driver Hub still has Power Management issues

  • Driver Hub needs battery compartment tweak to ensure internal battery makes good connection. Foam insert in battery compartment helps, but doesn’t always perfectly fix the problem.

  • Driver Hub cannot boot if the internal battery is too low, even if plugged into external battery. If battery dies, troubleshooting requires removal of battery to power device.

  • Power Management bugs can drain battery while charging.

• Driver Hub USB ports are fragile

  • Teams carrying their Driver Hubs around without a Driver Station tray (NOT RECOMMENDED) have dropped their Driver Hubs with gamepads plugged in, and impact can damage USB-A ports.

• Display screen ribbon cable comes loose

  • If the screen stops working, opening the back of the device and re-seating the screen ribbon cable can sometimes fix screen issues.

• Turning off the display unloads gamepad drivers, but turning the display back on does not reload them. USB devices must be re-plugged in order to trigger USB driver loading.

• USB-C to USB-C cables do not work with Driver Hub. USB-A to USB-C cables are required in order to use the USB-C port.

On the other hand, several off-the-shelf SmartPhones are supported, including the Motorola Moto E4 and Moto E5 phones. These devices, like the REV Driver Hub, run the Android mobile operating system and use Wi-Fi to talk to the REV Control Hub (therefore no SIM card or cell plan is required). SmartPhones use USB-OTG to interface with gamepads and external USB hubs necessary for operating multiple gamepads.

SmartPhone Pros

• SmartPhones are typically cheaper than Driver Hubs, and generally survive being dropped better.

• SmartPhones don’t have the same power management issues that Driver Hubs are known to have.

• Some teams report having better Wi-Fi consistency with SmartPhones than Driver Hubs, though that has not been verified or debunked in any way.

SmartPhone Cons

• There are only a small number of approved Android Smartphones, none of which are still supported by the manufacturers of the phones.

  • SmartPhones are deprecated typically within 2 years after being released. Security updates and OS updates are not guaranteed.

  • The number of approved SmartPhones are dwindling, and SmartPhones are becoming increasingly difficult to obtain. New SmartPhones are not being approved to replace older ones.

• Android is not a consistent platform in the Mobile Phone industry. Each manufacturer, and sometimes even within product families, will produce their own “flavor” of Android which has different software requirements and behaviors. Supporting the different manufacturers in the changing Android landscape is near impossible.

  • There is very little consistency between smartphones of the same model sold in different countries - each will have their own firmware with their own quirks, often impossible to debug or avoid.

  • FIRST Tech Challenge is not enough of a volume consumer to be able to set requirements or have partnerships with SmartPhone manufacturers.

• SmartPhones cannot use 802.11w for encryption of Wi-Fi control packets, which makes the connection between devices vulnerable. Rogue Access Point Detection and Quarantine features within venue network security systems (like within schools and other venues) can interrupt these communications seemingly randomly, making connections difficult to maintain.

• SmartPhones cannot be used at the same time they’re being charged, so teams frequently run down the internal batteries on the phones during the course of an event. Careful battery management is required.

  • PS4 and PS5 gamepads with internal batteries will further drain the SmartPhone batteries, as they leech power from the Driver Station in order to maintain a full charge level for their own batteries.

• SmartPhones require USB-OTG cables and external USB Hubs are also required in order to use multiple gamepads, and each cable/connection and device is a potential source of failure. Extreme care must be taken to ensure the connections remain solid.