CANary

A zero-configuration FRC robot program for electrical team QA. Deploy it, open RioLog, and read the report — or drop the single CANBusInspector.java file into your own robot project and call it whenever you need.

---

What it does

Passively listens to all CAN bus traffic and reports every device it sees:

Check	How
Which devices are present	Listens for status frames from each known manufacturer/type/ID combination
What each device is	Decodes manufacturer + device type from the CAN arbitration ID → human-readable name
Duplicate IDs	Flags any case where two devices of the same type share a CAN ID
Bus health	Reports utilization %, RX/TX error counts
NetworkTables output	Optionally publishes all results under the CANary table for dashboard use

---

How to run (standalone)

1. Deploy to the roboRIO via VS Code (Ctrl+Shift+P → WPILib: Deploy Robot Code)
2. Open Driver Station → View → RioLog
3. The report prints automatically every 10 seconds
4. The robot does not need to be enabled

---

Using in your own robot project

CANBusInspector.java is fully self-contained — it depends only on standard WPILib classes. You can copy the single file into any FRC Java project and call it directly.

Quick start

1. Copy src/main/java/frc/robot/CANBusInspector.java into your project's frc/robot/ package (or update the package declaration to match your own package).
2. Create an instance and call runInspection():

// In your Robot class or a command
CANBusInspector inspector = new CANBusInspector();

// Print report to RioLog only
inspector.runInspection();

// Print report AND push results to NetworkTables (under "CANary" table)
inspector.runInspection(true);

Periodic inspection example

Run the inspection on a timer (e.g. every 10 seconds) without blocking your main loop more than once per interval:

public class Robot extends TimedRobot {
    private final CANBusInspector inspector = new CANBusInspector();
    private static final double INSPECTION_INTERVAL_SECONDS = 10.0;
    private double lastInspectionTimestamp = 0.0;

    @Override
    public void robotPeriodic() {
        double now = Timer.getFPGATimestamp();
        if (now - lastInspectionTimestamp >= INSPECTION_INTERVAL_SECONDS) {
            lastInspectionTimestamp = now;

            // Print to RioLog only
            inspector.runInspection();

            // To also push results to NetworkTables, use the overload instead:
            // inspector.runInspection(true);
        }
    }
}

One-shot inspection example

Run the inspection once after a short boot delay to let all devices enumerate:

public class Robot extends TimedRobot {
    private final CANBusInspector inspector = new CANBusInspector();
    private boolean hasRun = false;

    @Override
    public void robotPeriodic() {
        if (!hasRun && Timer.getFPGATimestamp() > 5.0) {
            hasRun = true;
            inspector.runInspection();
        }
    }
}

Using scanBus() directly

If you need the raw device list for your own logic (e.g. pre-flight checks, dashboard widgets):

CANBusInspector inspector = new CANBusInspector();
List<CANBusInspector.DetectedDevice> devices = inspector.scanBus();

for (var device : devices) {
    System.out.println("Found: " + device.description() + " at ID " + device.deviceId());
}

---

NetworkTables output

When you call inspector.runInspection(true), results are published under the CANary NetworkTables table. You can view them in Shuffleboard, Glass, AdvantageScope, or any NetworkTables client.

Key	Type	Description
CANary/BusHealth/Utilization	double	Bus utilization (0–100%)
CANary/BusHealth/ReceiveErrors	int	Receive error count
CANary/BusHealth/TransmitErrors	int	Transmit error count
CANary/BusHealth/TxFullCount	int	TX-full count
CANary/BusHealth/Healthy	boolean	true when both error counters are zero
CANary/Devices	String[]	One entry per device: "ID | Name | Status"
CANary/Summary/DeviceCount	int	Total devices detected
CANary/Summary/DuplicateCount	int	Number of duplicate-ID groups
CANary/Summary/Result	String	"PASS", "FAIL", or "NO DEVICES"

Custom table path: Use the constructor overload new CANBusInspector(networkTable) to publish under a different NetworkTables path.

---

Example console output

==============================================================
  CAN BUS QA TOOL  —  Passive Device Scan
==============================================================
  Probing 1188 manufacturer/type/ID combinations...

--- BUS HEALTH ---
  Utilization:      9.2%
  Receive Errors:   0
  Transmit Errors:  0
  TX Full Count:    0
  Status:           ✓ HEALTHY

--- DETECTED DEVICES ---
  ID     Device                                    Status
  ------------------------------------------------------------
  0      Pigeon 2 IMU                              ✓ OK
  1      TalonFX (Kraken X60 / Falcon 500)         ✓ OK
  2      TalonFX (Kraken X60 / Falcon 500)         ✓ OK
  3      TalonFX (Kraken X60 / Falcon 500)         ✓ OK
  3      SPARK MAX / SPARK Flex                     ✗ DUPLICATE ID
  4      TalonFX (Kraken X60 / Falcon 500)         ✓ OK
  21     CANcoder                                   ✓ OK
  22     CANcoder                                   ✓ OK
  23     CANcoder                                   ✓ OK
  24     CANcoder                                   ✓ OK

--- SUMMARY ---
  Devices found:   10
  Duplicate IDs:   1

  *** RESULT: FAIL — Duplicate IDs must be resolved ***
    → Use Phoenix Tuner X or REV Hardware Client to
      reassign conflicting device IDs before handoff.

==============================================================

---

Fixing issues

Problem	Fix
No devices detected	Check CAN wiring (H/L reversed?), power to devices, termination resistors
Duplicate ID	Use Phoenix Tuner X (CTRE) or REV Hardware Client (REV) to reassign the ID
Expected device missing	Check that device's CAN connectors, power, and its own status LEDs
Unknown device shown	Add it to the DEVICE_NAMES lookup table in CANBusInspector.java
Bus errors at idle	Physical fault — check for shorts, missing termination, or a broken shield

---

How it works (for the curious)

Every FRC CAN device transmits periodic status frames. The 29-bit FRC CAN arbitration ID encodes:

[DeviceType: 5 bits][Manufacturer: 8 bits][APIClass: 6 bits][APIIndex: 4 bits][DeviceID: 6 bits]

WPILib's CAN class can open a receive filter for any (manufacturer, deviceType, deviceId) combination. This tool iterates over all known FRC manufacturer codes × device types × IDs 0–62, calls readPacketLatest() on each combination, and records any that have received a frame. The manufacturer + device type are then decoded into a human-readable name using a lookup table.

This is exactly the same principle used by Phoenix Tuner X and REV Hardware Client — just implemented as a deployable robot program that runs without a laptop connection.

---

Supported devices (out of the box)

• TalonFX (Kraken X60, Falcon 500) — CTRE
• CANcoder — CTRE
• Pigeon 2 IMU — CTRE
• CANdle LED Controller — CTRE
• CTRE PDH / PCM — CTRE
• SPARK MAX / SPARK Flex — REV
• REV Power Distribution Hub / Pneumatic Hub — REV
• navX-MXP / navX2 — Kauai Labs
• Redux Canandmag Encoder — Redux Robotics
• Playing With Fusion CANandcoder — PWF
• ThriftyNova Motor Controller — The Thrifty Bot
• Jaguar Motor Controller — Luminary Micro
• AndyMark PDB — AndyMark

Any unrecognized device will still show up as "[Manufacturer] [DeviceType]" — you can add a specific name to the DEVICE_NAMES map in CANBusInspector.java.

---

API reference

Method	Description
CANBusInspector()	Creates an inspector with results published to the default CANary NT table
CANBusInspector(NetworkTable)	Creates an inspector that publishes to a custom NetworkTables path
runInspection()	Scans the bus and prints a report to RioLog
runInspection(true)	Scans the bus, prints a report, and pushes results to NetworkTables
scanBus()	Returns a List<DetectedDevice> without printing anything — use for custom logic
DetectedDevice.description()	Human-readable device name (e.g. "TalonFX (Kraken X60 / Falcon 500)")
DetectedDevice.deviceId()	The 6-bit CAN ID (0–62)
DetectedDevice.duplicateKey()	Key for duplicate detection ("deviceType:id")

---

Dependencies

None beyond WPILib. This tool uses only edu.wpi.first.wpilibj.CAN, RobotController, and edu.wpi.first.networktables — all part of the standard WPILib installation. No vendor libraries required.