CAN Protocol

Note

This document describes the CAN Protocol. For examples of usage, check out our CAN Bus Guide.

Overview 

The ODrive CANSimple protocol uses standard 11-bit message identifiers.

CANSimple Message ID
- node_id: The node ID of the ODrive (<axis>.config.can.node_id). See Discovery & Addressing for details.
- cmd_id: The Command ID, identifying the message type. All available commands are listed in Messages.
Messages prefixed with Set_ are messages that the host can send to the ODrive.
Messages prefixed with Get_ are messages that the ODrive can send to the host. These messages can be enabled as Cyclic Messages or requested explicitly by the master. To explicitly request a message, the master sends a message with the RTR bit set, and the ODrive responds with the same ID and corresponding payload. (A message with of RTR=0 and an empty payload can also be used, but is susceptible to collisions with the ODrive’s response.)
All values are encoded in little endian (aka Intel format, aka least significant byte first).
Floats are encoded with the standard IEEE 754 Float format.
Reserved fields and padding in Host → ODrive messages must be set to 0.
Reserved fields and padding in ODrive → Host messages must be ignored.

CAN Messages - click on the message name for details
CMD ID	Name	Direction	Signals
0x000	Get_Version	ODrive → Host	Protocol_Version Hw_Version_Major Hw_Version_Minor Hw_Version_Variant Fw_Version_Major Fw_Version_Minor Fw_Version_Revision Fw_Version_Unreleased
0x001	Heartbeat	ODrive → Host	Axis_Error Axis_State Procedure_Result Trajectory_Done_Flag
0x002	Estop	Host → ODrive
0x003	Get_Error	ODrive → Host	Active_Errors Disarm_Reason
0x004	RxSdo	Host → ODrive	Opcode Endpoint_ID Reserved Value
0x005	TxSdo	ODrive → Host	Reserved0 Endpoint_ID Reserved1 Value
0x006	Address	Host → ODrive, ODrive → Host	Node_ID Serial_Number Connection_ID
0x007	Set_Axis_State	Host → ODrive	Axis_Requested_State
0x009	Get_Encoder_Estimates	ODrive → Host	Pos_Estimate Vel_Estimate
0x00b	Set_Controller_Mode	Host → ODrive	Control_Mode Input_Mode
0x00c	Set_Input_Pos	Host → ODrive	Input_Pos Vel_FF Torque_FF
0x00d	Set_Input_Vel	Host → ODrive	Input_Vel Input_Torque_FF
0x00e	Set_Input_Torque	Host → ODrive	Input_Torque
0x00f	Set_Limits	Host → ODrive	Velocity_Limit Current_Limit
0x011	Set_Traj_Vel_Limit	Host → ODrive	Traj_Vel_Limit
0x012	Set_Traj_Accel_Limits	Host → ODrive	Traj_Accel_Limit Traj_Decel_Limit
0x013	Set_Traj_Inertia	Host → ODrive	Traj_Inertia
0x014	Get_Iq	ODrive → Host	Iq_Setpoint Iq_Measured
0x015	Get_Temperature	ODrive → Host	FET_Temperature Motor_Temperature
0x016	Reboot	Host → ODrive	Action
0x017	Get_Bus_Voltage_Current	ODrive → Host	Bus_Voltage Bus_Current
0x018	Clear_Errors	Host → ODrive	Identify
0x019	Set_Absolute_Position	Host → ODrive	Position
0x01a	Set_Pos_Gain	Host → ODrive	Pos_Gain
0x01b	Set_Vel_Gains	Host → ODrive	Vel_Gain Vel_Integrator_Gain
0x01c	Get_Torques	ODrive → Host	Torque_Target Torque_Estimate
0x01d	Get_Powers	ODrive → Host	Electrical_Power Mechanical_Power
0x01f	Enter_DFU_Mode	Host → ODrive

The ODrive can be configured to send some messages periodically without a request from the host. This is done by setting the desired send intervals in <odrv>.axis.config.can. An interval of 0 disables the message. If the ODrive is unaddressed (node_id = 0x3f), all cyclic messages are disabled regardless of their configured interval.

Message	Configuration (`<odrv>.axis.config.can.[...]`)	Default Interval
Heartbeat	`heartbeat_msg_rate_ms`	100 ms
Get_Encoder_Estimates	`encoder_msg_rate_ms`	10 ms
Get_Iq	`iq_msg_rate_ms`	disabled
Get_Error	`error_msg_rate_ms`	disabled
Get_Temperature	`temperature_msg_rate_ms`	disabled
Get_Bus_Voltage_Current	`bus_voltage_msg_rate_ms`	disabled
Get_Torques	`torques_msg_rate_ms`	disabled

Watchdog 

The ODrive’s watchdog timer can be used as a safety feature to disable the motor when CAN communication is disrupted.

See axis.config.enable_watchdog on how to enable the watchdog timer.

The watchdog is reset by every Set_Input_Pos, Set_Input_Vel and Set_Input_Torque message, as well as when entering CLOSED_LOOP_CONTROL through Set_Axis_State.

Baudrate & Autobaud 

The ODrive’s baudrate (can.config.baud_rate) can either be explicitly configured by the user or left at 0 (default) to enable automatic baudrate detection (new in Firmware 0.6.11).

When using automatic baudrate detection, the ODrive starts in a “scanning mode” where it does not handle any CAN commands and does not send any CAN messages, but relies on incoming CAN traffic to detect the baudrate. For quick initialization, users are recommended to send a “beacon message” (any message ID / payload) at 10Hz or faster.

Once the scan completes, the ODrive responds normally to CAN messages and sends Cyclic Messages if applicable.

When the ODrive runs into a bus-off condition, it drops back into scanning mode.

In production systems it is recommended to configure the baudrate explicitily to guarantee deterministic startup time.

Supported baudrates for autodetection: 10kbps, 40kbps, 125kbps, 250kbps, 500kbps, 1Mbps.

Broadcast 

⇒ New in Firmware 0.6.9

The node ID 0x3f is a special broadcast address. When the host sends a message with this ID, it is received by all ODrives on the bus. If the broadcast message yields a response (typically Get_ messages with RTR=1), each ODrive responds with its own node_id.

If an ODrive is configured with node_id = 0x3f, it does not send out any cyclic messages or responses, except for the special message Address.

Discovery & Addressing 

⇒ New in Firmware 0.6.9

By default, an unconfigured ODrive starts with node_id = 0x3f, which represents an unaddressed state. In this state the ODrive does not send any cyclic messages (heartbeats, feedback, …).

The node ID can be configured:

Over USB using odrivetool or in the GUI.
Via CAN using automatic enumeration based on the Address (0x06) message. An interactive script for this is provided in Setting up the ODrive (CAN only) which should be sufficient for most commissioning scenarios.

Otherwise, a user application can implement its own procedure based on the use cases below.

Use cases:

Enumerate all ODrives on the bus:

Send (node_id = 0x3f, cmd_id = 0x06, RTR=1).

All ODrives that are already addressed (node_id != 0x3f) will respond immediately with their serial number and node_id.

All unaddressed ODrives (node_id == 0x3f) will respond after a small random delay, averaging 250 ms between each message.
Assign a new node ID (N) to an ODrive with unknown node ID and known serial number (SN):

Send (node_id = 0x3f, cmd_id = 0x06, Node_ID = N, Serial_Number = SN).

If the ODrive was at its default configuration, it will now start periodically sending Heartbeat and Get_Encoder_Estimates messages.
Assign a new node ID (new_N) to an ODrive with known node ID (old_N) and unknown serial number:

Send (node_id = old_N, cmd_id = 0x06, Node_ID = new_N, Serial_Number = 0).

Furthermore, the Identify field in Clear_Errors can be used to blink the status LED. This allows for setting up an interactive procedure that lets the user associate newly discovered unconfigured ODrives with their location in a multi-axis robot.

Bus-off handling 

“Bus-off” events are part of the CAN specification and are usually the result of a persistent fault condition on the CAN bus (e.g. short, disconnect or faulty bus node).

When the ODrive encounters a bus-off event, it reacts as follows:

if autobaud is enabled: Drops into scanning mode.
if autobaud is disabled: Restarts its CAN interface. If the fault condition persists, the CAN interface is restarted repeatedly. See also n_restarts.

DBC Files 

DBC files are machine-readable database files that describe CAN message formats.

The CANSimple .dbc file for each firmware version can be downloaded here.

Several tools and libraries exist to ingest DBC files. For example you can use the free CANdb++ software from Vector to view the database.

Interoperability with CANopen 

ODrives can coexist with CANopen devices on the same bus if caution is taken with the node ID assignment.

The following table lists the valid combinations of node IDs for both CANopen and CANsimple.

CANOpen node IDs	ODrive CANSimple node IDs
32 … 127	0x10, 0x18, 0x20, 0x28
64 … 127	0x10, 0x11, 0x18, 0x19, 0x20, 0x21, 0x28, 0x29
96 … 127	0x10, 0x11, 0x12, 0x18, 0x19, 0x1A, 0x20, 0x21, 0x22, 0x28, 0x29, 0x2A

Messages 

Get_Version

Command ID: 0x00
Direction: ODrive → Host

Start Byte	Name	Type	Description
0	Protocol_Version	uint8	Always reported as 2
1	Hw_Version_Major	uint8	`hw_version_major`
2	Hw_Version_Minor	uint8	`hw_version_minor`
3	Hw_Version_Variant	uint8	`hw_version_variant`
4	Fw_Version_Major	uint8	`fw_version_major`
5	Fw_Version_Minor	uint8	`fw_version_minor`
6	Fw_Version_Revision	uint8	`fw_version_revision`
7	Fw_Version_Unreleased	uint8	`fw_version_unreleased`

Heartbeat

Command ID: 0x01
Direction: ODrive → Host

Start Byte	Name	Type	Description
0	Axis_Error	uint32	`<axis>.active_errors` \| `<axis>.disarm_reason`
4	Axis_State	uint8	`<axis>.current_state`
5	Procedure_Result	uint8	`<axis>.procedure_result`
6	Trajectory_Done_Flag	uint8	`<axis>.controller.trajectory_done` (0: false, 1: true)

Estop

Command ID: 0x02
Direction: Host → ODrive
Empty Payload

Causes the axis to disarm with ESTOP_REQUESTED.

Get_Error

Command ID: 0x03
Direction: ODrive → Host

Start Byte	Name	Type	Description
0	Active_Errors	uint32	`active_errors`
4	Disarm_Reason	uint32	`disarm_reason`

RxSdo

Command ID: 0x04
Direction: Host → ODrive

Start Byte	Name	Type	Description
0	Opcode	uint8	0: read, 1: write
1	Endpoint_ID	uint16	Endpoint ID as found in `flat_endpoints.json`
3	Reserved	uint8	Must be set to 0
4	Value	uint32	Data type and length depend on endpoint ID

Sent by the host to read or write from/to arbitrary parameters. See Arbitrary Parameter Access for details.

TxSdo

Command ID: 0x05
Direction: ODrive → Host

Start Byte	Name	Type	Description
0	Reserved0	uint8	Must be ignored by host
1	Endpoint_ID	uint16	Endpoint ID as found in `flat_endpoints.json`
3	Reserved1	uint8	Must be ignored by host
4	Value	uint32	Data type and length depend on endpoint ID

Sent by the ODrive in response to an RxSdo with Opcode=READ. See Arbitrary Parameter Access for details.

Address

Command ID: 0x06
Direction: Host → ODrive, ODrive → Host

Start Byte

Name

Type

Description

0

Node_ID

uint8

node_id

1

Serial_Number

uint48

ODrive → Host: Serial number of the sending ODrive

Host → ODrive: The serial number that shall be associated with the specified Node_ID

7

Connection_ID

uint8

Connection ID. Can be left 0

Main section: Discovery & Addressing.

When an ODrive receives this message (subject to receive filters, that means node_id contained in the message ID must matches its own or be 0x3f), it takes the following action:

RTR=1 (or empty payload): Respond with own serial number and node_id.
Matching Serial_Number: Take on the new Node_ID.
Mismatching Serial_Number but matching Node_ID: Go to unaddressed state (node_id = 0x3f).
Mismatching Serial_Number and mismatching Node_ID: Ignore message.

Serial_Number == 0 is considered a wildcard that always matches.

Responses on this message are sent even if the ODrive is unaddressed (node_id = 0x3f). In this case, the response is sent after a random delay to avoid collisions.

Set_Axis_State

Command ID: 0x07
Direction: Host → ODrive

Start Byte	Name	Type	Description
0	Axis_Requested_State	uint32	`requested_state`

Get_Encoder_Estimates

Command ID: 0x09
Direction: ODrive → Host

Start Byte

Name

Type

Unit

Description

0

Pos_Estimate

float32

rev

<axis>.pos_vel_mapper.pos_rel or <axis>.pos_vel_mapper.pos_abs,

depending on ODrive.Controller.Config.absolute_setpoints

4

Vel_Estimate

float32

rev/s

<axis>.pos_vel_mapper.vel

This message is sent by the ODrive periodically by default. See also Cyclic Messages.

Set_Controller_Mode

Command ID: 0x0b
Direction: Host → ODrive

Start Byte	Name	Type	Description
0	Control_Mode	uint32	`control_mode`
4	Input_Mode	uint32	`input_mode`

Set_Input_Pos

Command ID: 0x0c
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Input_Pos	float32	rev	`input_pos`
4	Vel_FF	int16	0.001 rev/s (default) [1]	`input_vel`
6	Torque_FF	int16	0.001 Nm (default) [2]	`input_torque`

Set_Input_Vel

Command ID: 0x0d
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Input_Vel	float32	rev/s	`input_vel`
4	Input_Torque_FF	float32	Nm	`input_torque`

Set_Input_Torque

Command ID: 0x0e
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Input_Torque	float32	Nm	`input_torque`

Set_Limits

Command ID: 0x0f
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Velocity_Limit	float32	rev/s	`vel_limit`
4	Current_Limit	float32	A	`current_soft_max`

Set_Traj_Vel_Limit

Command ID: 0x11
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Traj_Vel_Limit	float32	rev/s	`vel_limit`

Set_Traj_Accel_Limits

Command ID: 0x12
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Traj_Accel_Limit	float32	rev/s^2	`accel_limit`
4	Traj_Decel_Limit	float32	rev/s^2	`decel_limit`

Set_Traj_Inertia

Command ID: 0x13
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Traj_Inertia	float32	Nm/(rev/s^2)	`inertia`

Get_Iq

Command ID: 0x14
Direction: ODrive → Host

Start Byte	Name	Type	Unit	Description
0	Iq_Setpoint	float32	A	`Iq_setpoint`
4	Iq_Measured	float32	A	`Iq_measured`

Get_Temperature

Command ID: 0x15
Direction: ODrive → Host

Start Byte	Name	Type	Unit	Description
0	FET_Temperature	float32	deg C	`<axis>.motor.fet_thermistor.temperature`
4	Motor_Temperature	float32	deg C	`<axis>.motor.motor_thermistor.temperature`

Reboot

Command ID: 0x16
Direction: Host → ODrive

Start Byte

Name

Type

Description

0

Action

uint8

0: reboot()

1: save_configuration()

2: erase_configuration()

3: enter_dfu_mode2()

Reboots the ODrive according to Action. This requires the axis to be in IDLE.

Get_Bus_Voltage_Current

Command ID: 0x17
Direction: ODrive → Host

Start Byte	Name	Type	Unit	Description
0	Bus_Voltage	float32	V	`vbus_voltage`
4	Bus_Current	float32	A	`ibus`

Clear_Errors

Command ID: 0x18
Direction: Host → ODrive

Start Byte	Name	Type	Description
0	Identify	uint8	`identify`

Equivalent to calling clear_errors().

Set_Absolute_Position

Command ID: 0x19
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Position	float32	rev	`pos_estimate`

Set_Pos_Gain

Command ID: 0x1a
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Pos_Gain	float32	(rev/s) / rev	`pos_gain`

Set_Vel_Gains

Command ID: 0x1b
Direction: Host → ODrive

Start Byte	Name	Type	Unit	Description
0	Vel_Gain	float32	Nm / (rev/s)	`vel_gain`
4	Vel_Integrator_Gain	float32	Nm / rev	`vel_integrator_gain`

Get_Torques

Command ID: 0x1c
Direction: ODrive → Host

Start Byte	Name	Type	Unit	Description
0	Torque_Target	float32	Nm	`effective_torque_setpoint`
4	Torque_Estimate	float32	Nm	`torque_estimate`

Get_Powers

Command ID: 0x1d
Direction: ODrive → Host

Start Byte	Name	Type	Unit	Description
0	Electrical_Power	float32	W	`electrical_power`
4	Mechanical_Power	float32	W	`mechanical_power`

Enter_DFU_Mode

Command ID: 0x1f
Direction: Host → ODrive
Empty Payload

Puts the ODrive into DFU mode (see Firmware Update). Equivalent to calling enter_dfu_mode2().