CAN Protocol
CAN Communication
Baud-Rate
The CAN communication baud-rate is 1Mbps.
Non-Periodic Communication
Messages can be sent to initialize
or stop CAN communication.
Remote frame can be used to request data.
If host sends remote frame, the Allegro Hand responds with it regardless periodic communication status.
Periodic Communication
The Allegro Hand control software attempts to communicate with the real or simulated hand at a regular control interval.
Every 3 milliseconds, the joint torques are calculated and the joint angles are updated.
CAN Frames
Arbitration Identifier
The Allegro Hand uses 11 bit standard arbitration identifier.
It is composed with two part.
Message ID
Messages marked with RTR can be sent by host in remote frame, and the Allegro Hand will respond it.
Device ID
Multiple Allegro Hand can be used in the same CAN bus.
In such case, Device ID field is used to distinguish each device.
Default device ID is 0, and it can be configured using Config message.
Changed Device ID is stored in internal non-volatile memory and will be retained for power cycle.
Data Structure
Each message has different data filed format.
All multi-byte data structures in data filed uses little endian
Servo ON
Data Length = 0
This message does not have data field.
Servo OFF
Data Length = 0
This message does not have data field.
Set Torque Finger #
Data Length = 8
Each finger has 4 joints. This message sets joint torque set-point. Torque set-point is 2 byte signed digit. Data field is composed as below.
Set Position Finger #
Data Length = 8
Each finger has 4 joints. This message sets position set-point. Position set-point is 2 byte signed digit. Data field is composed as below.
This message is not implemented yet.
Set Periodic Read
Data Length = 8
This message sets periodic report interval. Period is configured in milli-second. If period is set to 0, that message will not be reported periodically.
Config
Data Length = 6
This message sets Device ID and RS-485 baud-rate. If SET field bit is marked, corresponding data will be stored in internal non-volatile memory.
SET field is structured as below.
Dev.ID field is structured as below.
Baud-rate field is structured as below.
Information
Data Length = 7
Information message is composed with hardware version, firmware version, palm temperature, status flag. The Allegro Hand sends this message when the host request by remote frame.
Hardware Ver. And Firmware Ver. Is 2 byte number.
L/R field shows which side hand is. If this field is 0, it means the Hand is right hand.
Temp field shows palm temperature. Represented in signed Celsius degree.
Stat field represents current status. The same data can be retrieved using Status message.
-
S : Servo status. 0 means servo OFF.
-
F1 : One or more of joints is in high temperature fault state.
-
F2 : One or more of joints is in high temperature throttling state.
-
F3 : One or more of joints is in communication timeout state.
-
F4 : Palm is in high temperature fault state.
Serial
Data Length = 8
Serial number can be retrieved using CAN interface. It is stored in ASCII characters.
The Allegro Hand sends this message when the host request by remote frame.
Position Finger #
Data Length = 8
Joint position is reported through this message format. The Allegro Hand sends this message when the host request by remote frame or report period comes. All values are represented as signed 2 byte integer.
Joint angle can be calculated by this equation
Temperature Finger #
Data Length = 4
The temperature of joint is reported through this message format. The Allegro Hand sends this message when the host request by remote frame or report period comes. All values are represented as signed 1 byte integer.
Temperature is represented as Celsius degree.
Status
Data Length = 1
Hand Status can be retrieved by this message. The Allegro Hand sends this message when the host request by remote frame or report period comes.
Status bit field is same with Stat field in Information message.