CanControl

CanControl is a library for controlling CAN-based motor controllers (REV Spark MAX, CTRE Talon SRX, Victor SPX) from Arduino boards using an MCP2515 CAN Shield. CanControl currently supports:

• REV Robotics Spark MAX (full support)
• CTRE Talon SRX (PercentOutput only)
• CTRE Victor SPX (PercentOutput only)

It handles the necessary FRC-style "Heartbeat" frames and providing high-level wrappers, so you can control FRC motor controllers without a roboRIO.

Features

• High-level C++ wrappers:
  • CanControl::SparkMax
  • CanControl::TalonSrxMotor
  • CanControl::VictorSpxMotor
• Universal heartbeat frames to keep FRC motor controllers enabled.
• Full features from the SparkMax
  • Low-level Spark MAX CAN protocol is auto-generated from REV's JSON spec (see gen.py and third_party/REV-Specs/).
• CTRE (Talon SRX / Victor SPX) support — percent/duty-cycle only
  • CTRE integration is implemented from the only available public example for percent output; no further official CAN protocol docs were provided by CTRE.

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Hardware

1. Arduino Board: tested with Arduino Uno and Arduino Mega 2560.
2. MCP2515 CAN Module: Standard SPI-based CAN controller board (often labeled "TJA1050 + MCP2515").
3. CAN Motor Controller: REV Spark MAX, CTRE Talon SRX, or Victor SPX.
4. 120Ω Termination Resistor: CRITICAL. You MUST have a 120Ω resistor connected between CAN-H and CAN-L at the ends of your bus to prevent signal reflection.

Wiring Instructions

MCP2515 Connections

The MCP2515 communicates via SPI. Connect it to your Arduino as follows:

Pin Name	Arduino Uno Pin	Arduino Mega Pin	Description
VCC	5V	5V	Power
GND	GND	GND	Ground
CS	10	53	Chip Select (Configurable in main.cpp)
SO / MISO	12	50	Master In Slave Out
SI / MOSI	11	51	Master Out Slave In
SCK	13	52	SPI Clock
INT	2 (Optional)	2 (Optional)	Interrupt (not strictly required for basic TX)

CAN Bus Wiring

1. CAN High (H): Connect MCP2515 H to Motor Controller Yellow wire.
2. CAN Low (L): Connect MCP2515 L to Motor Controller Green wire.
3. Termination: Ensure a 120Ω resistor connects H and L at the furthers point of the bus (often the MCP2515 itself has a jumper for this, check your module). In any case, you must have a resistor on both ends of the bus.

Note: Spark MAX controllers do not have built-in termination. You must add the resistor yourself if it's the last device in the chain.

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Installation & Usage

Using as a library in your own PIO project

In your own platformio.ini:

[env:mega]
platform = atmelavr
framework = arduino
board = megaatmega2560

lib_deps =
    https://github.com/willGuimont/CanControl.git

Using with Arduino IDE

Coming soon...

Cloning and Building (Development)

git clone https://github.com/willGuimont/CanControl.git
cd CanControl
git submodule update --init --recursive

Build and Upload (PlatformIO)

Open the project in VS Code with PlatformIO.

For Arduino Uno:

pio run -e uno -t upload

For Arduino Mega:

pio run -e mega -t upload

Usage

The example sketch (examples/main.cpp) immediately starts a "Heartbeat" to keep motors enabled. You can control a motor using the Serial Monitor (Baud Rate: 115200).

Serial Commands:

• s0.5: Set Speed to 50%
• s-0.5: Set Speed to -50%
• s0: Stop Motor
• h: Help menu

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CTRE Talon SRX & Victor SPX

Using CTRE devices requires that they be "FRC unlocked" to accept non-FRC frames. The FRC lock will be enabled by default and be persistent across power cycles if the device was ever connected to an FRC roboRIO. To unlock the device, you need to disconnect it from the roboRIO and power it while holding the reset button for about 5 seconds until the LED blinks green.

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Generated Spark MAX Low-Level API

The low-level Spark MAX protocol bindings are generated from doc/spark-frames-2.1.0.json (available from REVrobotics/REV-Specs) by gen.py and live in:

• include/low_level/low_sparkmax.h
• src/low_level/low_sparkmax.cpp

These files are auto-generated (see the header comment) and should not be edited by hand. Instead, update the JSON spec or generator and re-run gen.py.

The high-level SparkMax class in include/sparkmax.h wraps these generated structures to provide a user-friendly C++ API.

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Analysis Tools

Located in the tools/ directory (install requirements with pip install pyserial):

• can_monitor.py: Live monitor that talks to the Arduino sketch to print/log CAN traffic.

  python tools/can_monitor.py --port COM3 --output log.csv

• compare_logs.py: Compare two CSV logs to find timing differences or missing messages.

  python tools/compare_logs.py good_log.csv bad_log.csv

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Testing

This project uses PlatformIO's Unity-based test framework.

Run tests on your host (native):

pio test -e native -v

Run embedded tests on the board (e.g. Mega 2560):

pio test -e mega -v

The native tests live under test/test_native, and embedded tests under test/test_embedded.

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Troubleshooting

• "Sticky Fault for CAN Bus Error": This usually means missing termination. Add a 120Ω resistor between Green/Yellow wires.
• Motor LEDs Flashing Orange/Green: The motor is seeing some valid frames but timing out frequently. Check wiring and termination or heartbeat frequency.
• CTRE Motors: Must be Factory Defaulted or not "FRC Locked". If they were used on a roboRIO, hold the B/C button on boot to factory reset.

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