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answer contains an explanation of how servos are managed on a Control and
Expansion Hub that you cannot get anywhere else!


.. dropdown:: Week of 12/18/2023 "Automatic Auto to Driver Control Program Switching"

Did you know that it’s possible for the Driver Station to
:ref:`automatically load your Driver Controlled OpMode
<programming_resources/shared/auto_load_opmode/auto-load-opmode:Automatically
Loading a Driver Controlled Op Mode>` as soon as your Autonomous OpMode has
completed? Lots of teams go into panic mode immediately after Autonomous has
completed - they’re trying to navigate and select the proper Driver
Controlled OpMode, Initialize, and Run the OpMode while also picking up
their gamepads and preparing to drive. Skip all that panic and confusion and
let the Driver Station queue up your Driver Controlled OpMode for you! This
week’s Tech Tip of the Week focuses on how to :ref:`designate a Driver-Controlled
OpMode <programming_resources/shared/auto_load_opmode/auto-load-opmode:Automatically
Loading a Driver Controlled Op Mode>` that is to be loaded once an Autonomous OpMode has completed. You
still have to initialize and run the OpMode at the proper time, but at least
the Driver Station can do the heavy lifting of swapping and loading the
OpMode for you!

.. dropdown:: Week of 12/25/2023 "Protect your Robot with a Password"

This week’s Tech Tip of the Week is a gentle reminder that strong passwords
and regular backups make for good competition. Even when competing at a
Scrimmage before your competition season starts, be sure to change your
Wi-Fi password on your Control Hub from the default password of “password”
to something only your team knows. Anyone who knows your password can easily
gain access to your robot and change or delete your programs, change
important settings, or even force your controller to revert to factory
settings! And with that said, it’s ALWAYS a good idea to keep backups of
your programs - it’s especially important to regularly
:ref:`download all Blocks
<programming_resources/tutorial_specific/blocks/managing_opmodes/managing-opmodes:downloading an opmode>`
and OnBot Java programs that are normally only stored on the robot in case
anything happens!

.. dropdown:: Week of 01/08/2024 "OnBot Java Backups"

This week’s Tech Tip of the Week is for all those who program in OnBot Java.
Have you ever been worried that your OnBot Java programs could suddenly
magically vanish? Has it ever happened to you? One lesser-known feature of
OnBot Java is automatic backups - each time you “compile all” in OnBot Java
the system saves a copy of all source code, up to 30 compilations deep. In
order to find these backups, you must connect to the Control Hub via USB
from a Windows machine and navigate to the “FIRST” folder on the device’s
internal storage. In this folder you’ll find a “java” folder, and within
that is the “srcBackups” folder. Here you’ll find zip files containing each
backup with a time/date stamp. Happy Programming!

.. dropdown:: Week of 01/22/2024 "REV Grounding Strap"

This week’s Tech Tip of the Week is dedicated to the `REV Resistive
Grounding Strap <https://www.revrobotics.com/rev-31-1269/>`__; the REV
Resistive Grounding Strap (RGS) is the only FTC-legal means of providing a
grounding option for your robot frame or connected structural elements.
Static electricity has two basic behaviors depending on whether it’s
building up on a conductive or non-conductive surface; on non-conductive
surfaces like polycarbonate or other plastics static electricity builds up
in “pools”, on conductive surfaces like most metals static electricity
spreads and distributes across the entire surface of the material. Aluminum
extrusion used on robots typically has a clear non-conductive anodized layer
used to prevent corrosion of the aluminum but the aluminum under the layer
is conductive. When using the RGS, it’s important to connect the RGS to
surfaces where you want to mitigate static buildup. If mounting the RGS to
aluminum on your robot, it’s recommended to use a `multimeter
<https://www.amazon.com/KAIWEETS-Multimeter-Resistance-Capacitance-Temperature/dp/B07SHLS639>`__
to test the continuity between the ring terminal on the RGS to different
places on the robot to determine if the static buildup will be mitigated by
the RGS. If testing for resistivity, remember that the REV Grounding Strap
has a 470 Ohm resistor (with a ~5% tolerance) in-line in the strap - if not
using an auto-range multimeter, be sure to select a range above 600 Ohms to
ensure the resistivity is measured properly. It may be necessary to scrape
the aluminum to create a conductive path between multiple segments of
aluminum, just remember that a non-conductive oxide layer will eventually
form on the exposed aluminum. Remember that if you're probing aluminum
extrusion to check for continuity or resistivity, those areas need to be
scraped to expose bare metal in order to ensure electrical connectivity.
“Jumper wires” screwed to aluminum elements can also be added to ensure
conductivity between components.

.. dropdown:: Week of 01/29/2024 "REV Driver Hub Tips"

Welcome to the Tech Tip of the Week! This week is a long one, filled with
great REV Driver Hub tips. Most everything here can be found in REV’s Driver
Hub Troubleshooting tips page, we’ve just annotated a few of these for the
most common scenarios you’ll potentially experience with the REV Driver Hub.
Understand that this Tip of the Week is not meant to disparage the REV
Driver Hub in any way - no device is perfect, but the REV Driver Hub can
provide you trouble-free performance if you can understand its nuances and
take a few additional steps to keep it running optimally.

1. Make sure your REV Driver Hub time/date is set correctly! This is the cause
of a number of inspection nightmares and Robot Controller log file
confusion, the first step should always be to check to make sure the
Date/Time on the Driver Hub is set correctly. This is set through the normal
Android System Settings by pulling down the Android Quick Settings pull-down
twice, tapping the Gear Icon, selecting System, and then selecting “Date &
Time”.

2. USB wall chargers are all the same, right? Wrong. A/C-to-USB wall
chargers can range drastically in power (measured in Watts) - the REV
Driver Hub comes with an A/C-to-USB wall charger, and that is the
recommended wall charger to use to charge the REV Driver Hub. Can you
use another device to charge the REV Driver Hub? Maybe, but it’s best
to stick to either the one that ships with the REV Driver Hub or a
fully-charged USB Battery Pack like the `Anker 10,000mA Power Bank
<https://www.amazon.com/Anker-Ultra-Compact-High-Speed-VoltageBoost-Technology/dp/B07QXV6N1B>`__
which can keep a Driver Hub fully charged all day without ever needing
to put the Driver Hub to sleep.

3. Rechargeable Lithium batteries don’t necessarily work the same way that
other batteries work, they all have a slightly different usable
Voltage range. The REV Driver Hub needs to calibrate to the Voltage
range of the internal lithium battery plugged into it, and to do that
there’s a full `calibration process
<https://docs.revrobotics.com/duo-control/troubleshooting-the-control-system/driver-hub-troubleshooting/driver-hub-battery-troubleshooting#battery-calibration>`__
that has to be followed for any new battery, along with a
`verification step
<https://docs.revrobotics.com/duo-control/troubleshooting-the-control-system/driver-hub-troubleshooting/driver-hub-battery-troubleshooting#battery-verification>`__.
DO NOT simply “replace” a drained battery with a new charged one when
it gets low, the new battery is NOT guaranteed to have the same
calibration as the first and it is not guaranteed to perform
optimally. If you’re having problems keeping the REV Driver Hub
internal battery charged, consider a USB Battery Pack like the `Anker
10,000mA Power Bank
<https://www.amazon.com/Anker-Ultra-Compact-High-Speed-VoltageBoost-Technology/dp/B07QXV6N1B>`__.

4. Battery safety in any Lithium Battery system is paramount, and the REV
Driver Hub has battery safety features that most teams will likely run
into at least once. The most commonly experienced safety feature is
the `Battery Lockout system
<https://docs.revrobotics.com/duo-control/troubleshooting-the-control-system/driver-hub-troubleshooting/driver-hub-battery-troubleshooting#battery-lockout-recovery>`__.
If a REV Battery depletes to a level below its recommended safe level,
or the battery is overcharged, the REV Driver Hub will enter lockout
mode to protect the battery. In this mode, the REV Driver Hub will not
power on when the battery button is held down. The process for
recovering from Battery Lockout can take several minutes, but it’s
better than the alternative. It’s not recommended to leave a REV
Driver Hub on charge unattended for more than 8-10 hours, and
definitely NOT for multiple days.

5. When a user puts the REV Driver Hub to sleep, or if it goes to sleep on
its own because the Driver Station App main screen is not actively
running in the foreground, it goes to sleep pretty easily. However,
when the REV Driver Hub returns from a sleep state, sometimes the
Wi-Fi and the gamepads will not reload correctly or automatically;
this requires you to unplug and replug the gamepads from the REV
Driver Hub before you can use them again, or perform a hard reboot in
order to bring Wi-Fi connectivity back. Many veteran teams use a
fully-charged USB Battery Pack, like the `Anker 10,000mA Power Bank
<https://www.amazon.com/Anker-Ultra-Compact-High-Speed-VoltageBoost-Technology/dp/B07QXV6N1B>`__,
and leave the Driver Station App main screen running all day without
putting the device to sleep.

6. Keep the REV Driver Hub safe by using 3M Dual-Lock or hook-and-loop
fasteners (like those sold by Velcro Brand) to mount the Driver Hub to
a `Driver Station Carrier
<https://www.andymark.com/products/18-in-driver-station-tray>`__. This
prevents your REV Driver Hub from being placed on the floor (where team
members may step on it) and prevents you from accidentally dropping the
Driver Hub on the floor - dropping the Driver Hub is the #1 cause of all
Driver Hub damage! Some teams have designed their own
`custom <https://www.thingiverse.com/thing:3386378>`__
`Driver <https://www.thingiverse.com/thing:5439041>`__
`Station <https://www.facebook.com/TeamWolfCorp/photos/a.1627476360819953/3028421417392100/?type=3>`__
`Carriers <https://jmhannon.myportfolio.com/ftc-driver-station>`__,
be creative and have fun!

7. When the REV Driver Hub is not in use (not at competitions, not in use
during practices) it should be turned OFF and have all sources of
power disconnected. Do not put the Driver Hub to sleep, but actually
turn it off - press the power button for 1-2 seconds and then use the
drop-down menu to turn off the device. The Driver Hub uses power even
in sleep mode, and that can lead to a dead battery and you may have to
perform `Battery Lockout Recovery
<https://docs.revrobotics.com/duo-control/troubleshooting-the-control-system/driver-hub-troubleshooting/driver-hub-battery-troubleshooting#battery-lockout-recovery>`__
before you can turn it back on.

8. Sometimes teams may experience “random power loss” on the REV Driver
Hub. This is usually due to a battery fitment issue within the battery
box on the device (the battery momentarily stops making a connection
with the power pins on the device), and can be mitigated using
`techniques
<https://docs.revrobotics.com/duo-control/troubleshooting-the-control-system/driver-hub-troubleshooting#option-1-tape-quick-fix>`__
from the REV Troubleshooting tips. Some teams have been known to operate
their REV Driver Hubs without a battery inserted at all, and simply run
the Driver Hub using a fully-charged USB Battery Pack, like the `Anker
10,000mA Power Bank
<https://www.amazon.com/Anker-Ultra-Compact-High-Speed-VoltageBoost-Technology/dp/B07QXV6N1B>`__.
The jury is still out on whether that’s a good idea, but worth
considering if you’re having problems that you’re desperate to solve and
REV Support is unable to help you resolve (because of time pressures)
before your big event.

9. Ensure your REV Driver Hub is fully updated. Firmware 1.2.0 solves a
host of REV Driver Hub issues, and it makes sense to use the on-board
updater (once connected to Wi-Fi) to perform all updates on the Driver
Hub.

10. This isn’t specifically a REV Driver Hub tip, but it’s a question we get
asked all the time. Did you know that the Robot Wi-Fi network name
(Robot Controller Name) and the Wi-Fi passwords can be managed
straight from within the Driver Station app? With the Driver Station
App connected via Wi-Fi to the Robot Controller, click on the three
dots menu on the upper-right and select “Program and Manage”, then
use the hamburger menu on the upper-left and select “Manage”. On this
page you’ll find all of the same settings as you’d find on the
webpage by logging in to the controller on a laptop!

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