Acronyms Galore: Wired for Success Advanced FRC Robot Wiring

Agenda – Advanced FRC Robot Wiring AIO / DIO PWM Serial / I2C / SPI CAN TCP/IP ARGHHH

Analog & Digital Inputs / Outputs Analog inputs vary over a set input range, and are interpreted by the RoboRio over that range Digital inputs may vary slightly over the input range, but are interpreted only as ‘on’ or ‘off’ (or 1 or 0, High or Low, True or False, etc.)

AIOs and DIOs The RoboRio has some easily accessible DIO / AIO pins (along the edge), and some less easily accessible ones (in the MXP connector) Software controls whether the pin is an ‘input’ (reads voltage on the pin) or an ‘output’ (drives or sets the voltage on the pin)

Limit Switches: Digital IO Examples of AIO/DIO Limit Switches: Digital IO Potentiometer ‘absolute’ shaft encoders: Analog IO Ultrasonic SRF04s: Digital IO Spikes: Digital IO

This is where ‘protocols’ come in! Sometimes you need to convey more than just ‘on and off’ or a ‘analog’ value This is where ‘protocols’ come in! English is a protocol for modulating sound waves to convey meaning Similarly, everything we are about to talk about is a protocol to convey information via electrical signals

Pulse Width Modulation One of the simpler protocols: The duration of the ‘on’ cycle vs the duration of the ‘off’ cycle conveys the information For servos and motor controllers in FRC, this cycle repeats at a known frequency with a known minimum and maximum pulse width

Examples of PWM LED Dimming: (Brightness = On duration / Off duration * max led brightness) Servo signals PWM Motor controllers

Many flavors of Serial communication RS-232: Single Ended, Point to Point RS-422: Differential Signaling, Point to Point RS-485: Differential Signaling, Multipoint Bottom Line: Unless you have a really good reason to use it, don’t

Two signals: (Aka a “two wire” serial bus) I2C Inter-Integrated Circuit (I2C) is a multi- master, multi-slave […] serial bus for ‘low speed’ communication Used a lot for sensors Two signals: (Aka a “two wire” serial bus) Serial Clock (SCL) Serial Data (SDA)

Used a lot for sensors, and memory SPI Serial Peripheral Interface (SPI) is a single master, multiple slave serial bus for ‘mid speed’ communication Used a lot for sensors, and memory (At least) four signals: (aka a “four wire” serial protocol) Serial Clock (SCLK) Master Out, Slave In (MOSI) Master In, Slave Out (MISO) Slave Select

Microcontrollers (e.g., Arduinos!) “Smart” batteries Examples of I2C / SPI (Some) LIDARs: I2C SD Cards: SPI Microcontrollers (e.g., Arduinos!) “Smart” batteries

CAN Controller Area Network (CAN) is a microprocessor oriented message based protocol originating in vehicles Two signals: CAN-H (CAN High) CAN-L (CAN Low)

RoboRio, PCM, PDP all communicate via CAN Examples of CAN RoboRio, PCM, PDP all communicate via CAN Talon SRXs and SD540Cs are CAN based motor controllers Kauai VMX-Pi, CTR-E Hero, and certain microcontrollers

TCP / IP Transmission Control Protocol (TCP) and the Internet Protocol (IP) are a suite of standards that underly modern computer networking Simply put, they do a *lot* of magic in making sure that the data you wanted sent from point A to point B gets there in good shape

The Internet (well, most of it…) Examples of TCP / IP The Internet (well, most of it…) How you hook your Robot and Driver Station to the FRC Field Management System (with some exceptions…) Usually how you communicate with co-processors

We just wired our robot, and something isn’t working! What do we do?! AARGH! We just wired our robot, and something isn’t working! What do we do?! Troubleshooting to the rescue! Troubleshooting is a Team sport Don’t be so sure it’s someone else’s fault!

Troubleshooting Steps If any component lets out the magic smoke, that is your first clue… After you (immediately) turn the robot off, don’t replace the faulty part until you figure out *why* the magic smoke came out Double and Triple check for reverse polarity wiring, too high a voltage, shorts, metal shavings, and other reasons that electricity could go where it should not

Troubleshooting steps Check your basic wiring Are there loose crimps? Wires coming out of their housings? Did pin 3 plug into pin 2 by accident? Did you tug test every wire and every connector? Especially if something is intermittent, check: That crimps did not break the copper of the wire That the wire is conductive despite how its bent Are the battery terminals loose?

Check your basic code Check code: Did you open and close communication protocol sessions appropriately? Are they configured for the right ports, pins, speeds, polarities? Are you transmitting and receiving the right amount of data? Are you timing out somewhere in your code? Did you read the manual to make sure you know what functions you are calling?

Make sure to note observations: Check Robot Condition Make sure to note observations: Does the battery need charging? (if the robot is disabled, the battery should read >~12V) Does the ‘wacky thing’ only happen when you turn right, lower the lift or activate the shooter? If so, make sure you don’t have a code or mechanical issue!

If the previous ‘basic’ steps did not help, breakout the tools! Investigative Tools If the previous ‘basic’ steps did not help, breakout the tools! Multimeters are every team’s friend! For advanced wackiness, you might need to break out advanced tools, like logic analyzers, oscilloscopes, network sniffers, etc.