FRC 2015 Control System Notes

• FRC, FRC2015

These are notes I took while watching the FRC Behind the Lines episode "2015 Control System Beta Teams" (https://www.youtube.com/watch?v=uUYlS2Vkyuo) They are organized into broad categories, but are otherwise not cleaned up.

Hardware

  • RoboRio (hardware)
    • CAN built in
    • NXP port
      • add additional I/O
      • Integrated w/ WpiLib - hardware ports are 0-9; NXP is 10+
      • Must be broken out w/ custom PCB
  • CAN
    • Asynchronous - refreshes automatically
      • Default refresh rates (configurable)
        • Jaguar: 20ms
        • CAN talon: 10ms
    • Monitoring on driver station
    • Can check % utilization & other statistics on webdash (below), to determine fault causes
  • Power distribution board
    • Blinky yellow light for brownout
    • More intelligent (connects to RoboRIO via CAN)
    • Per-port current sensing - see what's using power
  • Voltage regulator module
    • 2A spec is max peak (momentary) - only 1½A continuous
    • RoboRio prevents itself from switching off by detecting brownout and switching off other subsystems
      • 6.3-6.8V — 5v power rail — servos, sensors
      • 4.5-6.3V — PWM/CAN controllers, relays
        • This can cause stuttering as they cause brownouts, switch off, recover; lather, rinse, repeat.
      • Lower voltages: RoboRIO itself switches off, then WiFi bridge
      • Recovers quickly (<100ms?)
  • Weidmuller connectors
    • Wire whiskers can cause intermittent shorts
      • Will mostly occur on the field, not in pits, due to vibration
    • Wires: strip to 8mm; shorter sizes can cause issues. Recommend tinning wires
    • Insertion/removal can cause wires to bunch up and not connect as well

Software

  • RoboRio - Software
    • User button - can be programmed to do anything
      • e.g. reset sticky faults (see below)
    • Web Dashboard
      • http://roborio-3173/
      • Update RoboRio firmware
      • CAN bus:
        • List devices
        • Update firmwares
        • See device info
        • control devices manually
      • Sticky faults
        • Must be cleared manually
        • e.g.: brownouts cause yellow blinky light on PDB
        • Can also reset faults from code
      • Many other features
    • Running Linux; configured as real-time OS
      • Can set priorities on tasks (e.g. drives=very important; logging=not as important)
      • 3rd party libraries (e.g. OpenCV)
      • Has package mananger: opkg
        • Connect RoboRio to Internet, use to download & install additional software
      • Can install anything you like manually
    • 2 cores! - spin up another thread via WpiLib tasks or Linux pthreads API
  • Driver station
    • Lots more data displayed
    • Multicast DNS (mDNS)
      • Special dlink setup tool (like last year)
      • dlink now has DHCP server, issues IP addresses to any connected device
        • no more manual IP configuration! — Plug & play!
      • Reserved block for manual allocation if necessary
  • Programming — Java SE 8 embedded (up from JRE 1.3 (!))
    • Lambda expressions! Enums! Etc! (No more MissingMath!)
    • API - WPIlib
      • Very backward-compatible
      • 0-indexed instead of 1