CanControl

CanControl is an Arduino library for controlling FRC CAN motor controllers using an SPI-based MCP2515 CAN module, no roboRIO required.

Project homepage.

Supported controllers

Controller	Support
REV Spark MAX	High-level control and generated low-level bindings from REV-Specs
CTRE Talon SRX / Victor SPX	PercentOutput only, based on CTRE's public HERO example

Hardware and wiring

You need an Arduino Uno or Mega, an MCP2515 CAN module, and a supported motor controller. The quick start below uses a Mega, Spark MAX with CAN ID 1, and an 8 MHz MCP2515 module.

MCP2515 Pinout

Pin	Arduino Uno	Arduino Mega	Description
VCC	5V	5V	Power
GND	GND	GND	Ground
CS	10	53	Chip Select
SO (MISO)	12	50	SPI Data Out
SI (MOSI)	11	51	SPI Data In
SCK	13	52	SPI Clock

CAN Bus Wiring

1. CAN-H: MCP2515 H -> Motor Controller Yellow wire.
2. CAN-L: MCP2515 L -> Motor Controller Green wire.
3. Bus Termination: Place a 120Ω resistor across CAN-H and CAN-L at each physical end of the bus (MCP2515 boards usually have an onboard jumper for one end).
4. Oscillator Frequency: Set MCP_8MHZ, MCP_16MHZ, or MCP_20MHZ to match the physical crystal on your MCP2515 board.

Note

REV Spark MAX Configuration: Configure device CAN IDs, motor type (Brushed/Brushless), idle mode, and firmware using the REV Hardware Client over a direct USB-C connection to your PC.

Important

CTRE Configuration & FRC Lock:

• CAN ID Setup: Set the device CAN ID using CTRE Phoenix Tuner, typically while connected to a roboRIO or CTRE CAN interface.
• FRC Lock & Unlocking: Whenever a CTRE motor controller operates on an FRC network with a roboRIO, it automatically becomes FRC locked and persists this state across power cycles, causing it to ignore non-FRC control frames. To use it with CanControl, disconnect it from the roboRIO, then power on the controller while holding the reset (B/C) button for ~5 seconds until the LED blinks green to unlock the device.

Quick start

1. Install

Add CanControl to your project's platformio.ini:

[env:mega]
platform = atmelavr
framework = arduino
board = megaatmega2560
lib_deps =
    willguimont/CanControl@^1.3.2

2. Run one motor

Put this sketch in src/main.cpp. It commands 25% duty cycle while sending periodic heartbeats. Match the CS pin and oscillator to your wiring; for Uno, use board = uno above and CS pin 10 below.

#include <CanControl.h>
#include <SPI.h>
#include <mcp2515.h>

MCP2515 mcp2515(53, 4000000UL); // Mega CS pin 53, 4 MHz SPI
CanControl::SparkMax motor(mcp2515, 1);

void setup()
{
    mcp2515.reset();
    mcp2515.setBitrate(CAN_1000KBPS, MCP_8MHZ); // Match module oscillator
    mcp2515.setNormalOneShotMode();
}

void loop()
{
    static unsigned long last_heartbeat = 0;
    if (millis() - last_heartbeat >= 20)
    {
        CanControl::send_heartbeat(mcp2515, CanControl::default_heartbeat());
        last_heartbeat = millis();
    }

    motor.set_duty_cycle(0.25f);

    delay(5);
}

Upload with pio run -e mega -t upload. This minimal sketch omits error reporting; the full example includes initialization checks and serial diagnostics.

Other APIs and examples

API	Header	Use when
Direct	<CanControl.h>	Controlling one motor with a simple sketch, as above
Queued	<can_controller.h> + <motors_queued/...>	Controlling multiple motors with automatic scheduling
Stateless commands	<commands.h>	Minimizing memory use and managing scheduling yourself

Direct and stateless calls require you to schedule heartbeats and space commands to avoid filling the MCP2515 transmit buffers. Queued control handles this when you call can_controller.update(dt_ms) regularly from loop(); it does not run in the background.

For CTRE motors, periodic global enable is also required. See examples for CTRE calls, complete sketches, serial commands, and memory measurements.

Troubleshooting

Symptom	What to check
Bus errors	CAN-H/CAN-L wiring and 120Ω termination at each end
No traffic	CS pin, SPI wiring, and oscillator setting (MCP_8MHZ, MCP_16MHZ, or MCP_20MHZ)
Motor does not enable	Configured CAN ID, periodic heartbeat, and CTRE global enable / FRC lock where applicable
Intermittent operation	Heartbeat timing, command spacing, and regular update() calls in queued mode

Development

See CONTRIBUTING.md for tests, protocol generation, CAN logging tools, and publishing instructions.

License

GNU General Public License v3.0 only (GPL-3.0-only).