The FTC Control System
Components
Robots in FTC are controlled using Android phones. The Robot Controller phone is secured on the robot and connected to all of its electronics, whereas the Driver Station is kept with the drivers and connected to the game controllers. These two phones communicate with each other using WiFi Direct.
Robot Controller
The Robot Controller phone is responsible for controlling the robot and making decisions using sensor inputs, which is what your code will accomplish. Our code runs on the FTC Robot Controller app, which is what we upload onto the Robot Controller phone. You do not need to worry about wireless communication—that is handled by the app, not your code.
Driver Station
The Driver Station phone acts like a television remote. It allows you to control the execution of OpModes, configure hardware, and view telemetry data remotely. It runs the FTC Driver Station app. Your code should never make its way onto this phone directly—we accidentally uploaded to a Driver Station once, and the result was disastrous!
Types of 12V Connectors
Before we dive into the hardware controllers, we need to familiarize ourselves with a few types of connectors that deliver power from the 12V robot battery to the various components of the robot.
Anderson Powerpole
The Anderson Powerpole (or simply Powerpole) connector is the most popular power delivery connector in FTC. It typically delivers at least 12V to the various hardware controllers and motors of the robot.
XT30
The XT30 connector is primarily found on REV products only. It delivers power from the 12V robot battery to the REV Expansion Hubs.
Tamiya
The Tamiya connector is probably the second most popular connector in modern FTC. Most competition-legal batteries have a Tamiya interface.
JST VH
The JST VH connector connects REV Expansion Hubs to various 12V motors. They only deliver power.
Hardware Controllers
Hardware controllers act as the middleman between the Robot Controller and the individual hardware devices. We connect the Robot Controller to one or more hardware controllers, which connect to specific motors, servos, and sensors.
As of 2020-2021, ARC has one main type of hardware controller: REV Expansion Hubs.
REV Expansion Hub
Unlike the Modern Robotics system, the REV Expansion Hub combines the adapters for all types of peripherals into one unit. Each unit supports four motors, six servos, two analog sensors, four digital sensors, and four I²C sensors. Typically, each competition robot has two Expansion Hubs that are connected to each other using this process.
All motor encoder ports and sensor ports run at 3.3 volts in the REV ecosystem. To use any sensor or encoder that needs 5 volts to function correctly, a level shifter is needed to convert the voltage.
Info
Many of our motors have encoders that require 5 volts to function. Our NeveRest 40s, for example, have built-in encoders that function incorrectly when only 3.3 volts are supplied. When your RUN_USING_ENCODER or RUN_TO_POSITIONmodes do not function correctly, this could be the culprit!
REV's official guide to the Expansion Hub is a great reference for peripheral compatibility and troubleshooting purposes.
Check your Understanding
- What's the difference between the Robot Controller and the Driver Station? What are their respective roles?
- How do control signals travel from the driver's joystick to the motors on the robot? Describe the entire process.
- What is the name of the hardware controller used in ARC?