Introduction

To control DYNAMIXEL, communication should be established according to the protocol of DYNAMIXEL. DYNAMIXEL is driven by receiving binary data. Examples of programs for the transmission of this kind of data are described in detail in the User’s Manual of DYNAMIXEL-only controller or the USB2DYNAMIXEL. Thus, this manual describes only the method and protocol of communication used in DYNAMIXEL on the assumption that Main Controller can transfer binary data.

• DYNAMIXEL Protocol 2.0 supported devices: MX-28, MX-64, MX-106, X Series (2X Series included), PRO Series, P Series.
• DYNAMIXEL Protocol 2.0 supported controllers: CM-50, CM-150, CM-200, OpenCM7.0, OpenCM9.04, CM-550, OpenCR, OpenRB-150
• Other: 2.0 protocol from R+ Smart app, DYNAMIXEL Wizard 2.0

TIP : See DYNAMIXEL Protocol Compatibility Table.

Note: MX(2.0) is a special firmware for the DYNAMIXEL MX series supporting the DYNAMIXEL Protocol 2.0. The MX(2.0) firmware can be upgraded from the Protocol 1.0 by using the Firmware Recovery in DYNAMIXEL Wizard 2.0.

Packet

Main Controller and DYNAMIXEL communicate each other by sending and receiving data called Packet. Packet has two kinds: Instruction Packet, which Main Controller sends to control DYNAMIXEL, and Status Packet, which DYNAMIXEL responses to Main Controller.

ID

ID is a specific number for distinction of each DYNAMIXEL when several DYNAMIXEL’s are linked to one bus. By giving IDs to Instruction and Status Packets, Main Controller can control only DYNAMIXEL that you want to control

DYNAMIXEL Protocol

DYNAMIXEL does the Asynchronous Serial Communication with 8 bit, 1 Stop bit, and None Parity.

If DYNAMIXEL with the same ID is connected, packet will collide and network problem will occur. Thus, set ID as such that there is no DYNAMIXEL with the same ID. To change the DYNAMIXEL’s ID, reference the DYNAMIXEL Control Table section in the DYNAMIXEL Wizard 2.0.

NOTE: The DYNAMIXEL’s initial ID is 1 at the factory condition.

Half Duplex

Half duplex UART is a serial communication protocol where both TxD and RxD cannot be used at the same time. This method is generally used when many devices need to be connected to a single bus. Since more than one device are connected to the same bus, all the other devices need to be in input mode while one device is transmitting. The Main Controller that controllers DYNAMIXEL actuators sets the communication direction to input mode, and only when it is transmitting an Instruction Packet, it changes the direction to output mode.

Tx, Rx Direction

For Half Duplex UART, the transmission ending timing is important to change the direction to receiving mode. The bit definitions within the register that indicates UART_STATUS are as the following

• TXD_BUFFER_READY_BIT: Indicates that the transmission DATA can be loaded into the Buffer. Note that this only means that the SERIAL TX BUFFER is empty, and does not necessarily mean that the all the data transmitted before has left the CPU.
• TXD_SHIFT_REGISTER_EMPTY_BIT: Set when all the Transmission Data has completed its transmission and left the CPU.

The TXD_BUFFER_READY_BIT is used when one byte is to be transmitted via the serial communication channel, and an example is shown below.

  TxDByte(byte bData)
  {
    while(!TXD_BUFFER_READY_BIT); //wait until data can be loaded.
    SerialTxDBuffer = bData; //data load to TxD buffer
  }

When changing the direction, the TXD_SHIFT_REGISTER_EMPTY_BIT must be checked. The following is an example program that sends an Instruction Packet

1  DIRECTION_PORT = TX_DIRECTION;
2  TxDByte(0xff);
3  TxDByte(0xff);
4  TxDByte(0xfd);
5  TxDByte(0x00);
6  TxDByte(bID);
7  TxDByte(bLengthLow);
8  TxDByte(bLengthHigh);
9  TxDByte(bInstruction);
10  TxDByte(Parameter0); TxDByte(Parameter1); ...
11  TxDByte(bCrcLow);
12  DisableInterrupt(); // interrupt should be disable
13  TxDByte(bCrcHigh);  // last TxD
14  while(!TXD_SHIFT_REGISTER_EMPTY_BIT); // Wait till last data bit has been sent
15  DIRECTION_PORT = RX_DIRECTION; // Direction change to RXD
16  EnableInterrupt(); // enable interrupt again

WARNING : Please note the important lines between LINE 12 and LINE 16. Line 12 is necessary since an interrupt here may cause a delay longer than the return delay time and corruption to the front of the status packet may occur.

Byte to Byte Time

The delay time between bytes when sending an instruction packet. If the delay time is over 1.5ms, then DYNAMIXEL actuator recognizes this as a communication problem and waits for the next header (0xff 0xff 0xfd) of a packet again.

Instruction Packet

Instruction Packet is the command packet sent to the Device.

Header

The field that indicates the start of the Packet

Reserved

Uses 0X00 (Note that Reserved does not use 0XFD). The Reserved functions the same as Header.

See the next image of a table of the Packet Details of the DYNAMIXEL Wizard 2.0, which shows that the Reserved (0x00) are included in the Header field.

A table of Packet Details of DYNAMIXEL Wizard 2.0

Packet ID

The field that indicates an ID of the device that should receive the Instruction Packet and process it

1. Range : 0 ~ 252 (0x00 ~ 0xFC), which is a total of 253 numbers that can be used
2. Broadcast ID : 254 (0xFE), which makes all connected devices execute the Instruction Packet

WARNING: Be sure that Broadcast ID(254 (0xFE)) return Status Packet for Ping, Sync Read and Bulk Read only, other [Instruction] aside from Ping, Sync Read and Bulk Read will not return Status Packet to Broadcast ID.

Length

The field that indicates the length of packet field.

1. Devided into low and high bytes in the Instruction Packet
2. The Length indicates the Byte size of Instruction, Parameters and CRC fields

• Length = the number of Parameters + 3
• Status Packet includes 1 byte length ERROR field’s data.

Instruction

The field that defines the type of commands.

Parameters

1. As the auxiliary data field for Instruction, its purpose is different for each Instruction.
2. Method of expressing negative number data : This is different for each product, so please refer to the e-manual of the corresponding product.

CRC

16bit CRC field which checks if the Packet has been damaged during communication.

1. Devided into low and high bytes in the Instruction Packet
2. Range of CRC calculation: From Header (FF FF FD 00) to Parameteres before CRC field in Instruction Packet
3. Calculating CRC and examples: CRC Calculation

Status Packet

Status Packet is the response packet transmitted from the device to a main controller. Note that it has the same construction as the Instruction Packet except the ERROR field is added.

Instruction

Instruction of the Status Packet is designated to 0x55 (Status)

Error

The field that indicates the processing result of Instruction Packet

• Alert : When there is some hard ware issue with the Device, this field is set as 1. Checking the Hardware error status value of the Control Table can indicate the cause of the problem.
• Error Number : When there has been an Error in the processing of the Instruction Packet.

Parameters

1. As the auxiliary data field for Instruction, its purpose is different for each Instruction.
2. Method of expressing negative number data : This is different for each product, so please refer to the e-manual of the corresponding product

Response Policy

1. Broadcast ID(254 (0xFE)) is responded to Ping, Sync Read and Bulk Read only. For instance, Broadcast ID is not responded to Sync Write and Bulk Write Instruction.
2. A response to Instruction can be determined depending on a value of Status Return Level in Control Table. For more details, see the selectable value from Status Return Level in Control Table of the DYNAMIXEL in use.

Packet Process

Processing Order of Transmission

1. Generate basic form of Packet and afterwards Byte Stuffing(0xFD)
   • Inspection range : Everything within the Instruction field to the Parameter field (not the CRC)
   • Processing method : When the pattern “0xFF 0xFF 0xFD” appears, add Byte Stuffing (0xFD) (If “0xFF 0xFF 0xFD” already exists, add a 0xFD to change it to “0xFF 0xFF 0xFD 0xFD”)
2. Length : Modify to Length with Byte Stuffing applied
3. CRC : Calculate CRC with Byte Stuffing applied

Processing Order of Reception

1. Search for Header(0xFF 0xFF 0xFD) : Ignore the Byte Stuffing(“0xFF 0xFF 0xFD 0xFD”).
2. Packet ID : If Packet ID is valid, receive additional transmission the size of Length
3. CRC : Calculate with the received Packet with Byte Stuffing included, and once CRC is matched then remove Byte Stuffing

Instruction Details

Note that given examples use the following abbreviation to provide clear information.

• Header : H
• Reserved: RSRV
• Length: LEN
• Instruction: INST
• Error: ERR
• Param: P

Ping (0x01)

Description

• Instruction to check the existence of a Device and basic information
• Regardless of the Status Return Level of the Device, the Status Packet is always sent to Ping Instruction.
• When the Packet ID field is 0xFE(Broadcast ID) : All devices send their Status Packet according to their arranged order.

Packet Parameters

Note : Status Packet is received from each Device.

Example 1

Conditions

• ID1(XM430-W210) : For Model Number 1030(0x0406), Version of Firmware 38(0x26)
• Instruction Packet ID : 1

Ping Instruction Packet

ID 1 Status Packet

Example 2

Conditions

• ID1(XM430-W210) : For Model Number 1030(0x0406), Version of Firmware 38(0x26)
• ID2(XM430-W210) : For Model Number 1030(0x0406), Version of Firmware 38(0x26)
• Instruction Packet ID : 254(Broadcast ID)

Ping Instruction Packet

ID 1 Status Packet

ID 2 Status Packet

Read (0x02)

Description

• Instruction to read a value from Control Table
• Method of expressing negative number data : This is different for each product, so please refer to the e-manual of the corresponding product
• Read Instruction does not respond to Broadcast ID(254 (0xFE))

Note: If requesting the response for the excess range of its Control Table, the Status packet will fill Access Error in its error field, and return the packet with no parameters.

Packet Parameters

Example

Conditions

• ID1(XM430-W210) : Present Position(132, 0x0084, 4[byte]) = 166(0x000000A6)

Read Instruction Packet

ID 1 Status Packet

Write (0x03)

Description

• Instruction to write a value on the Control Table
• Method of expressing negative number data : This is different for each product, so please refer to the e-manual of the corresponding product

Packet Parameters

Example

Conditions

• ID1(XM430-W210) : Write 512(0x00000200) to Goal Position(116, 0x0074, 4[byte])

Write Instruction Packet

ID 1 Status Packet

Reg Write (0x04)

Description

• Instruction that is similar to Write Instruction, but has an improved synchronization characteristic
• Write Instruction is executed immediately when an Instruction Packet is received.
• By using Reg Write and Action Instruction, one can operate multiple devices simultaneously.
• Reg Write Instruction registers the Instruction Packet to a standby status, and sets Control table Registered Instruction to ‘1’.
• When an Action Instruction is received, the registered Packet is executed, and sets Control Table Registered Instruction to ‘0’.

Packet Parameters

Example

Condition

• ID1(XM430-W210) : Write 200(0x000000C8) to Goal Velocity(104, 0x0068, 4[byte])

Reg Write Instruction Packet

ID 1 Status Packet

Action (0x05)

Description

• Instruction that executes the Packet that has been registered using Reg Write Instruction
• When controlling multiple devices using Write Instruction, there will be a difference in the time of execution between the first device that receives the Packet and the last device that receives the Packet.
• By using Reg Write and Action Instruction, one can operate multiple devices simultaneously.

Example

Condition

• ID1(XM430-W210) : Instruction has been already registered by the Reg Write Instruction.

Action Instruction Packet

ID 1 Status Packet

Factory Reset (0x06)

Description

• Instruction that resets the Control Table to its initial factory default settings.
• When Factory Reset (0x06) Instruction is performed, a device is rebooted and the LED blinks four times in a row.
• In case of when Packet ID is a Broadcast ID 0xFE and Option is Reset All 0xFF, Factory Reset Instruction(0x06) will NOT be activated.
  • This feature is applied from MX(2.0) FW42, X-series FW42 or above.

Parameters

Example

Conditions

• ID1(XM430-W210) : Apply reset with option 0x01(Reset all except ID)

Factory Reset Instruction Packet

ID 1 Status Packet

Reboot (0x08)

Description

• Instruction to reboot the device

Example

Conditions

• ID1(XM430-W210)

Reboot Instruction Packet

ID 1 Status Packet

Clear (0x10)

Description

• This instruction resets certain information of DYNAMIXEL
• Supported DYNAMIXEL : MX (2.0) with Fw v42 or above, DYNAMIXEL-X series with Fw v42 or above

Parameters

Example

Conditions

• ID1(XM430-W210) : Resets multi turn revolution information

Clear Instruction Packet

ID 1 Status Packet

Control Table Backup (0x20)

Description

• Instruction to store current Control Table status data to a Backup area, or to restore EEPROM data.
• The Control Table Backup works properly only if Torque Enable in RAM area is set as ‘0’ (Torque Off status). If the Torque Enable is set as ‘1’ (Torque On), Status Packet with Result Fail will be returned.
• Supported DYNAMIXEL: X430/540 Series(Fw v45 or above), X330 Series(Fw v46 or above), P Series(Fw v12 or above).
• Available items in Control Table for data backup:
  • All Data in EERPOM
  • Velocity P.I Gains
  • Position P.I.D Gains
  • Feedforward 1st & 2nd Gains
  • Profile Acceleration
  • Profile Velocity
  • Indirect Addresses (Except DYNAMIXEL-P Series)

Parameters

Example

Example 1 Conditions

• ID 1(XC330-T288) : Backup the Control Table.

Control Table Backup Packet

ID1 Status Packet

Example 2 Conditions

• ID1(XC330-T288) : Restoring EEPROM data
• DYNAMIXEL will be rebooted after a successful restoration.

Control Table EEPROM Restoring Packet

ID1 Status Packet

Sync Read (0x82)

Description

• Instruction to read data from multiple devices simultaneously using one Instruction Packet
• The Address and Data Length of the data must all be the same.
• If the Address of the data is not continual, an Indirect Address can be used.
• Status Packet will be returned in order, according to input ID in the Instruction Packet.
• Packet ID field : 0xFE (Broadcast ID)

Parameters

Note : Each device individually returns Status Packet for Sync Read instruction.

Example

Conditions

• ID1(XM430-W210) : Present Position(132, 0x0084, 4[byte]) = 166(0x000000A6)
• ID2(XM430-W210) : Present Position(132, 0x0084, 4[byte]) = 2,079(0x0000081F)

Sync Read Instruction Packet

ID 1 Status Packet

ID 2 Status Packet

Sync Write (0x83)

Description

• Instruction to control multiple devices simultaneously using one Instruction Packet
• The Address and Data Length of the data must all be the same.
• If the Address of the data is not continual, an Indirect Address can be used.
• Packet ID field : 0xFE (Broadcast ID)

Parameters

Example

Conditions

• ID1(XM430-W210) : Write 150(0x00000096) to Goal Position(116, 0x0074, 4[byte])
• ID2(XM430-W210) : Write 170(0x000000AA) to Goal Position(116, 0x0074, 4[byte])

Sync Write Instruction Packet

Fast Sync Read (0x8A)

Description

• Enhanced Instruction for faster communication compared to Sync Read
• One Status Packet is structured and returned for all DYNAMIXELs if using Fast Sync Read Instruction regardless of number of DYNAMIXELs chained, as if one DYNAMIXEL returns Status Packet.
• Instruction Packet is formatted in the same way as Sync Read
• Supported DYNAMIXEL:
  • X430/540 Series (Fw v45 or above, 2XL/2XC Not Supported)
  • X330 (Fw v46 or above)
  • P Series (Fw v12 or above)
  • RH-P12-RN(A) (Fw v13 or above)

Note: DYNAMIXEL Tips | Use Fast Sync and Fast Bulk Read Instruction for Speedy Communication

Parameter

Note: CRC values are used for internal calculation in DYNAMIXEL to confirm packet integrity between DYNAMIXELs. You can let the main controller check CRC only at the end of Status Packet.

Note: Each device respectively returns a particular part of Status Packet in response to Fast Sync Read Instruction. For more details, see Example below.

Note: Fast Sync Read Status Packet does not perform Byte Stuffing(0xFD) process.

Example

Example Description

• ID3(XC330-T288) : Present Position(132, 0x0084, 4[byte]) = 166(0x000000A6)
• ID7(XC330-T288) : Present Position(132, 0x0084, 4[byte]) = 2,079(0x0000081F)
• ID4(XC330-T288) : Present Position(132, 0x0084, 4[byte]) = 1,023(0x000003FF)

Fast Sync Read Instruction Packet

ID 3 Status Packet

ID 7 Status Packet

ID 4 Status Packet

Bulk Read (0x92)

Description

• Similar to Sync Read, this is an Instruction to read data from multiple devices simultaneously using one Instruction Packet
• This Instruction can be used even if the Address and Data Length of the data for each device are not all the same.
• The same ID cannot be used multiple times in the Parameter. In other words, it can only read once from each individual device.
• Status Packet will be returned in order, according to input ID in the Instruction Packet.
• If the Address of the data is not continual, an Indirect Address can be used.
• Packet ID field : 0xFE (Broadcast ID)

Parameters

Note : Each device individually returns Status Packet for Bulk Read instruction. See the Example below for more details.

Example

Condition

• ID1(XM430-W210) : Present Voltage(144, 0x0090, 2[byte]) = 119(0x0077)
• ID2(XM430-W210) : Present Temperature(146, 0x0092, 1[byte]) = 36(0x24)

Bulk Read Instruction Packet

ID 1 Status Packet

ID 2 Status Packet

Bulk Write (0x93)

Description

• Similar to Sync Write, this is an Instruction to control multiple devices simultaneously using one Instruction Packet
• This Instruction can be used even if the Address and Data Length of the data for each device are not all the same.
• The same ID cannot be used multiple times in the Parameter. In other words, it can only write once for each individual device.
• If the Address of the data is not continual, an Indirect Address can be used.
• Packet ID field : 0xFE (Broadcast ID)

Parameters

Example

Condition

• ID1(XM430-W210) : Set Max Voltage Limit(32, 0x0020, 2[byte]) to 160(0x00A0)
• ID2(XM430-W210) : Set Temperature Limit(31, 0x001F, 1[byte]) to 80(0x50)

Bulk Write Instruction Packet

Fast Bulk Read (0x9A)

Description

• Enhanced Instruction for faster communication compared to Bulk Read.
• One Status Packet is structured and returned for all DYNAMIXELs using Fast Bulk Read Instruction regardless of number of DYNAMIXELs chained, as if one DYNAMIXEL returns Status Packet.
• Instruction Packet is formatted in the same way as Bulk Read
• Supported DYNAMIXEL:
  • X430/540 Series (Fw v45 or above, 2XL/2XC Not Supported)
  • X330 (Fw v46 or above)
  • P Series (Fw v12 or above)
  • RH-P12-RN(A) (Fw v13 or above)

Note: DYNAMIXEL Tips | Use Fast Sync and Fast Bulk Read Instruction for Speedy Communication

Parameters

Note: CRC values are used for internal calculation in DYNAMIXEL to confirm packet integrity between DYNAMIXELs. You can let the main controller check CRC only at the end of Status Packet.

Note: Each device respectively returns a particular part of Status Packet in response to Fast Bulk Read Instruction. For more details, see Example below.

Note: Status Packet responded from Fast Bulk Read does not perform Byte Stuffing(0xFD) process.

Example

Example Description

• ID3(XC330-T288) : Present Position(132, 0x0084, 4[byte]) = 166(0x000000A6)
• ID7(XC330-T288) : Present PWM(124, 0x007C, 2[byte]) = 421(0x01A5)
• ID4(XC330-T288) : Present Temperature(146, 0x0092, 1[byte]) = 31(0x1F)

Fast Bulk Read Instruction Packet

ID 3 Status Packet

ID 7 Status Packet

ID 4 Status Packet