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UART/RS485 Bus Servo Communication Protocol

v1.0.25

1. Introduction

This document introduces the UART/RS485 Bus servo communication protocol. The protocol uses asynchronous serial communication technology, providing a standardized solution for the transmission of control commands and status feedback between the master device and multiple servos.

1.1 Communication Mechanism

This protocol is based on half-duplex asynchronous serial communication, using 8 data bits, 1 stop bit, and no parity bit. During communication, TxD and RxD cannot be used simultaneously; therefore, only one device can transmit data at a time, while the other devices remain in receiving mode. This half-duplex communication mode is suitable for scenarios where multiple devices share the same communication bus.

1.2 Servo ID

In the entire communication system, each servo motor is assigned a unique ID for effective device addressing on the bus. The communication protocol uses a command-response mechanism to ensure reliable interaction in multi-device environments. The protocol defines the packet structure, parameter fields, checksum rules, and error handling methods in detail to ensure stable operation of the servos in various applications.

[!NOTE]

The default factory servo ID is 0.

1.3 Command Interval

To ensure stable communication, it is recommended that the command interval be between 5-10ms.

By ensuring a sufficient time interval, communication timeouts or errors can be effectively avoided, and reliable transmission of data packets is ensured.

2. Control Commands

Command Name Command ID Response Packet Type
Ping 01 (0x01) Fixed
Single-Turn Position Control (Basic) 08 (0x08) Optional
Single-Turn Position Control (Advanced – Time-based) 11 (0x0b) Optional
Single-Turn Position Control (Advanced – Speed-based) 12 (0x0c) Optional
Read Single-Turn Current Position 10 (0x0a) Fixed
Multi-Turn Position Control (Basic) 13 (0x0d) Optional
Multi-Turn Position Control (Advanced – Time-based) 14 (0x0e) Optional
Multi-Turn Position Control (Advanced – Speed-based) 15 (0x0f) Optional
Read Multi-Turn Current Position 16 (0x10) Fixed
Stop Instructions 24 (0x18) Optional
Reset Loop 17 (0x11) Optional
Damping Control 09 (0x09) Optional
Set Origin Point 23 (0x17) Optional
Synchronous Instruction 25 (0x19) /
Asynchronous Write Instruction 18 (0x12) Optional
Asynchronous Activate Instruction 19 (0x13) /
Read Data 03 (0x03) Fixed
Data Monitor 22 (0x16) Fixed
Customize Configuration Parameters 04 (0x04) Optional

3. Packet Structure

3.1 Command Packet

Command Packet is the standard data structure used by the master control to send control or query commands to the servo.

  • header: Fixed as 0x12 0x4C, used to identify the start of the command packet.
  • cmd_id: The control command for this packet.
  • length: Indicates the number of bytes of the subsequent data (content), used for packet parsing.

  • content: Stores control parameters (e.g., servo ID, target position, motion time, power, etc.), depending on the control command.

  • checksum: The result of adding all bytes and taking the modulo 256, used to check data integrity.

Communication Mechanism:
The master control sends a command packet to the servo to send control or read requests. After receiving a valid command packet, the servo parses the parameters and returns the corresponding Response Packet.

![command package](images_rs485/command package.svg)

3.2 Response Packet

Response Packet is the standard data structure returned by the servo to the master control after receiving and parsing a valid Command Packet. It contains the execution result and related data. The overall structure is the same as the command packet, but the starting position identifier and data content definitions differ.

  • header: Fixed as 0x05 0x1C, used to identify the start of the response packet.
  • cmd_id: The control command for this packet.
  • length: Indicates the number of bytes of the subsequent data (content), used for packet parsing.

  • content: Returns the execution result or corresponding data (e.g., current angle, voltage, temperature, version, read-back parameters, etc.), depending on the control command.

  • checksum: The result of adding all bytes and taking the modulo 256, used to check data integrity.

response_package

[!NOTE]

Response Packet Types

  • Fixed Response:Response packet is always returned.
  • Optional Response: Whether a response is returned depends on the PC configuration parameter Response after action(default = No).
  • Recommendation: For time-sensitive batch control scenarios (e.g., multi-servo synchronous control), it is recommended to disable configurable responses to reduce bus occupation. However, during debugging and fault diagnosis, enabling them is recommended for quick issue identification.

4. Data Types

Data Types Data Name Length Minimum Value Maximum Value
uint8_t Signed Short Int 1 0 255
uint16_t Unsigned Short Int 2 0 65,535
int16_t Signed Short Int 2 -32,768 32,767
uint32_t Unsigned Long Int 4 0 4,294,967,295
int32_t Signed Long Int 4 -2,147,483,648 2,147,483,647
uint8_t[n] Variable-Length Byte Array n

[!CAUTION]

The byte order used in the servo communication protocol is Little Endian. For example, a uint16_t value of 4,660, represented in hexadecimal as 0x1234, will be sent/received in the order of 0x34 0x12, with the low byte first and the high byte last.

5. Ping

5.1 Overview

  • By sending the Ping command for the corresponding servo motor ID, the status of whether the servo is online can be determined based on the response packet.

  • Command ID: 01 (0x01)

5.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Ping (0x01)
length 1 uint8_t 1 byte (0x01)
servo_id 1 uint8_t servo ID (range 0 ~ 254)
checksum 1 uint8_t checksum = Σ(Byte[0..4]) % 256

command_0x01

0x12 0x4c 0x01 0x01 0x00 0x60

Example Explanation:

  • Check if the servo with ID 0 is online.

5.3 Response

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x05 0x1c)
cmd_id 1 uint8_t Ping (0x01)
length 1 uint8_t 1 byte (0x01)
servo_id 1 uint8_t servo ID (range 0 ~ 254)
checksum 1 uint8_t checksum = Σ(Byte[0..4]) % 256

response_0x01

0x05 0x1c 0x01 0x01 0x00 0x23

Example Explanation:

  • Calculate and compare the theoretical checksum with the checksum in the response packet: If they match, then Servo with ID 0 is online.
  • It is recommended to set a maximum wait time timeout. If no response is received within this time, it indicates that the servo is offline.

6. Single-Turn Position Control (Basic)

6.1 Overview

  • Control the specified ID servo (or all servos) via the command to move to the target position (±180°) within the set motion time, and the execution power can also be set.

  • Command ID: 08 (0x08)

6.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Single-Turn Position Control (Basic) (0x08)
length 1 uint8_t 7 bytes (0x07)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
0xff represents all online servos
position 2 int16_t Target position, unit: 0.1°
range : +1800 ~ -1800 (+CW / −CCW)
time 2 uint16_t Motion time, unit: ms
power 2 uint16_t execution power, unit: mW
If power = 0 or exceeds the power protection value, the execution will follow the power protection value
checksum 1 uint8_t checksum = Σ(Byte[0..10]) % 256

command_0x08

0x12 0x4c 0x08 0x07 0x00 0x84 0x03 0xf4 0x01 0x00 0x00 0xe9

Example Explanation:

  • Set servo ID 0,
  • Move to the target position of +90° within 500ms,
  • Configure the power protection value to the maximum execution power, operating at maximum power.

6.3 Response (Optional)

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x05 0x1c)
cmd_id 1 uint8_t Single-Turn Position Control (Basic) (0x08)
length 1 uint8_t 2 bytes (0x02)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
result 1 uint8_t 0x01: Success execution| 0x00: Failure
checksum 1 uint8_t checksum = Σ(Byte[0..5]) % 256

response_0x08

0x05 0x1C 0x08 0x02 0x00 0x01 0x2c

Example Explanation:

  • The ID 0 servo returns a value of 0x01, indicating successful execution.

[!CAUTION]

By default, no response packet is returned. A response will only be sent if the servo configuration parameter Respond after action is set to Yes in the PC configuration.

7. Single-Turn Position Control (Advanced – Time-based)

7.1 Overview

  • Control the specified servo ID (or all servos) via command to move to the target position (±180°) within the set motion time. The execution power can be configured, and acceleration/deceleration parameters are supported to achieve trapezoidal speed profile motion.

  • Command ID: 11 (0x0b)

7.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Single-Turn Position Control (Basic) (0x0b)
length 1 uint8_t 11 bytes (0x0b)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
0xff represents all online servos
position 2 int16_t Target position, unit: 0.1°
range : +1800 ~ -1800 (+CW / −CCW)
time 2 uint16_t Motion time, unit: ms
accel 2 uint16_t Acceleration time, unit: ms
decel 2 uint16_t Deceleration time, unit: ms
power 2 uint16_t execution power, unit: mW
If power = 0 or exceeds the power protection value, the execution will follow the power protection value
checksum 1 uint8_t checksum = Σ(Byte[0..14]) % 256

[!WARNING]

The acceleration and deceleration time settings cannot be less than 20 ms, otherwise they will not take effect.

command_0x0b

0x12 0x4c 0x0b 0x0b 0x00 0x84 0x03 0x58 0x02 0x64 0x00 0xc8 0x00 0x00 0x00 0x81

Example Explanation:

  • Set servo ID 0,

  • Move to the target position of +90° within 500ms,

  • Acceleration time: 100 ms, deceleration time: 200 ms,

  • Configure the power protection value to the maximum execution power, operating at maximum power.

7.3 Response (Optional)

8. Single-Turn Position Control (Advanced – Speed-based)

8.1 Overview

  • Control the specified servo ID (or all servos) via command to move to the target position (±180°) within the set motion speed. The execution power can be configured, and acceleration/deceleration parameters are supported to achieve trapezoidal speed profile motion.

  • Command ID: 12 (0x0b)

8.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Single-Turn Position Control (Advanced – Speed-based) (0x0c)
length 1 uint8_t 11 bytes (0x0b)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
0xff represents all online servos
position 2 int16_t Target position, unit: 0.1°
range : +1800 ~ -1800 (+CW / −CCW)
speed 2 uint16_t Motion speed, unit: 0.1°/s
accel 2 uint16_t Acceleration time, unit: ms
decel 2 uint16_t Deceleration time, unit: ms
power 2 uint16_t execution power, unit: mW
If power = 0 or exceeds the power protection value, the execution will follow the power protection value
checksum 1 uint8_t checksum = Σ(Byte[0..14]) % 256

[!WARNING]

The acceleration and deceleration time settings cannot be less than 20 ms, otherwise they will not take effect.

command_0x0b

0x12 0x4c 0x0c 0x0b 0x00 0x84 0x03 0xd0 0x07 0x64 0x00 0xc8 0x00 0x00 0x00 0xff

Example Explanation:

  • Set servo ID 0,

  • Move to the target position of +90° at a motion speed of 200°/s,

  • Acceleration time: 100 ms, deceleration time: 200 ms,

  • Configure the power protection value to the maximum execution power, operating at maximum power.

8.3 Response (Optional)

9. Read Single-Turn Current Position

9.1 Overview

  • Read the current position of the servo with a specified ID via command. The returned value represents the single-turn current position (±180°) of the servo. This function can be used for real-time monitoring of the servo’s motion status.

  • Command ID: 10 (0x0a)

9.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Read Single-Turn Current Position (0x0a)
length 1 uint8_t 1 byte (0x01)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
checksum 1 uint8_t checksum = Σ(Byte[0..4]) % 256

command_0x08

0x12 0x4c 0x0a 0x01 0x00 0x69

Example Explanation:

  • Read Single-Turn Current Position of the servo with ID 0.

9.3 Response

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x05 0x1c)
cmd_id 1 uint8_t Read Single-Turn Current Position (0x0a)
length 1 uint8_t 3 bytes (0x03)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
position 2 int16_t Target position, unit: 0.1°
range : +1800 ~ -1800 (+CW / −CCW)
checksum 1 uint8_t checksum = Σ(Byte[0..6]) % 256

response_0x08

0x05 0x1C 0x0a 0x03 0x00 0x86 0x03 0xb7

Example Explanation:

  • The position value returned by the servo with ID 0 is 0x86 0x03. After unpacking, the obtained value is +902,
  • After converting it to the angular system, it indicates that the single-turn current position of the servo is +90.2°.

10. Multi-Turn Position Control (Basic)

10.1 Overview

  • Control the specified ID servo (or all servos) via command to move to the target position (±3,686,400°/1,024 turns) within the set motion time, and the execution power can also be set.

  • Command ID: 13 (0x0d)

10.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Multi-Turn Position Control (Basic) (0x0d)
length 1 uint8_t 11 bytes (0x0b)
servo_id 1 uint8_t servo ID, range 0 ~ 254(0x00 ~ 0xfc )
0xff represents all online servos
position 4 int32_t Target position, unit: 0.1°
range : +3,686,400 ~ -3,686,400 (+CW / −CCW)
time 4 uint32_t Motion time, unit: ms
power 2 uint16_t execution power, unit: mW
If power = 0 or exceeds the power protection value, the execution will follow the power protection value
checksum 1 uint8_t checksum = Σ(Byte[0..14]) % 256

command_0x08

0x12 0x4c 0x0d 0x0b 0x00 0xa0 0x0f 0x00 0x00 0x88 0x13 0x00 0x00 0x00 0x00 0xc0

Example Explanation:

  • Set servo ID 0,

  • Move to the target position of +400° within 5000ms,

  • Configure the power protection value to the maximum execution power, operating at maximum power.

10.3 Response (Optional)

11. Multi-Turn Position Control (Advanced – Time-based)

11.1 Overview

  • Control the specified servo ID (or all servos) via command to move to the target position(±3,686,400°/1,024 turns) within the set motion time. The execution power can be configured, and acceleration/deceleration parameters are supported to achieve trapezoidal speed profile motion.

  • Command ID: 14 (0x0e)

11.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Multi-Turn Position Control (Advanced – Time-based) (0x0e)
length 1 uint8_t 15 bytes (0x0f)
servo_id 1 uint8_t servo ID, range 0 ~ 254(0x00 ~ 0xfc )
0xff represents all online servos
position 4 int32_t Target position, unit: 0.1°
range : +3,686,400 ~ -3,686,400 (+CW / −CCW)
time 4 uint32_t Motion time, unit: ms
accel 2 uint16_t Acceleration time, unit: ms
decel 2 uint16_t Deceleration time, unit: ms
power 2 uint16_t execution power, unit: mW
If power = 0 or exceeds the power protection value, the execution will follow the power protection value
checksum 1 uint8_t checksum = Σ(Byte[0..18]) % 256

[!WARNING]

The acceleration and deceleration time settings cannot be less than 20 ms, otherwise they will not take effect.

command_0x0b

0x12 0x4c 0x0e 0x0f 0x00 0x70 0x17 0x00 0x00 0xb0 0x04 0x00 0x00 0x64 0x00 0x64 0x00 0x00 0x00 0x7e

Example Explanation:

  • Set servo ID 0,
  • Move to the target position of +600° within 1200ms,
  • Acceleration time: 100 ms, deceleration time: 100 ms,
  • Configure the power protection value to the maximum execution power, operating at maximum power.

11.3 Response (Optional)

12. Multi-Turn Position Control (Advanced – Speed-based)

12.1 Overview

  • Control the specified servo ID (or all servos) via command to move to the target position (±368,640°) within the set motion speed. The execution power can be configured, and acceleration/deceleration parameters are supported to achieve trapezoidal speed profile motion.
  • Command ID: 15 (0x0f)

12.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Multi-Turn Position Control (Advanced – Speed-based) (0x0f)
length 1 uint8_t 13 bytes (0x0d)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
0xff represents all online servos
position 4 int32_t Target position, unit: 0.1°
range : +3,686,400 ~ -3,686,400 (+CW / −CCW)
speed 4 uint32_t Motion speed, unit: 0.1°/s
accel 2 uint16_t Acceleration time, unit: ms
decel 2 uint16_t Deceleration time, unit: ms
power 2 uint16_t execution power, unit: mW
If power = 0 or exceeds the power protection value, the execution will follow the power protection value
checksum 1 uint8_t checksum = Σ(Byte[0..16]) % 256

[!WARNING]

The acceleration and deceleration time settings cannot be less than 20 ms, otherwise they will not take effect.

command_0x0b

0x12 0x4c 0x0f 0x0d 0x00 0x70 0x17 0x00 0x00 0xd0 0x07 0x64 0x00 0x64 0x00 0x00 0x00 0xa0

Example Explanation:

  • Set servo ID 0,
  • Move to the target position of +600° at a motion speed of 200°/s,
  • Acceleration time: 100 ms, deceleration time: 100 ms,
  • Configure the power protection value to the maximum execution power, operating at maximum power.

12.3 Response (Optional)

13. Read Multi-Turn Current Position

13.1 Overview

  • Read the current angle of the servo with a specified ID via command. The returned angle value represents the servo’s multi-turn current position (±3,686,400°), along with information on the number of turns (±1,024 turns). This function can be utilized for real-time monitoring of the servo’s motion status.
  • Command ID: 16 (0x10)

13.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Read Multi-Turn Current Position(0x10)
length 1 uint8_t 1 byte (0x01)
servo_id 1 uint8_t servo ID, range 0 ~ 254(0x00 ~ 0xfc )
checksum 1 uint8_t checksum = Σ(Byte[0..4]) % 256

command_0x08

0x12 0x4c 0x10 0x01 0x00 0x6f

Example Explanation:

  • Read Multi-Turn Current Position of the servo with ID 0.

13.3 Response

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x05 0x1c)
cmd_id 1 uint8_t Read Multi-Turn Current Position (0x10)
length 1 uint8_t 7 bytes (0x07)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
position 4 int32_t Target position, unit: 0.1°
range :+3,686,400 ~ -3,686,400 (+CW / −CCW)
turns 2 int16_t Lap information, unit: turn
range : -1024 ~ 1,024
checksum 1 uint8_t checksum = Σ(Byte[0..6]) % 256

response_0x08

0x05 0x1c 0x10 0x07 0x00 0x23 0x13 0x00 0x00 0x01 0x00 0x6f

Example Explanation:

  • The position value returned by the servo with ID 0 is 0x23 0x13 0x00 0x00. After unpacking, the obtained value is +4,899,
  • After converting it to the angular system, it indicates that the multi-turn current position of the servo is +489.9°,
  • The circle value returned by the servo with ID 0 is 0x10 0x00. After unpacking, the obtained value is 1，
  • Combined with the direction of the position value returned previously, it indicates that the current number of circles of the servo is 1 positive circle.

14. Stop Instructions

14.1 Overview

  • The stop instruction is utilized for rapid halting in servo motion control. Users can select different stop types according to their needs. This instruction can also be applied to restore the locking force after stall protection is triggered, as well as to re-establish the locking force at the current position when the locking force has been released.
  • Command ID: 24 (0x18)

14.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Stop Instructions (0x18)
length 1 uint8_t 4 bytes (0x04)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
mode 1 uint8_t Release locking force after stopping: 0x10
Maintain locking force after stopping: 0x11
Enter damping control after stopping: 0x12
power 2 uint16_t execution power, unit: mW
If power = 0 or exceeds the power protection value, the execution will follow the power protection value
checksum 1 uint8_t checksum = Σ(Byte[0..7]) % 256

command_0x01

0x12 0x4c 0x18 0x04 0x00 0x11 0x70 0x17 0x12

Example Explanation:

  • Set servo with ID 0 to enter the “stop motion” state,
  • With the stop mode set to 0x11, maintaining the locking force after stopping. The execution power is maintained at 6,000 mW (if the set power exceeds the power protection value, it will be executed according to the power protection value).

14.3 Response (Optional)

15. Reset Loop

15.1 Overview

  • Reset loop of the servo via command, and re-record the current absolute position as the present position.
  • Command ID: 17 (0x11)

15.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Reset Loop (0x11)
length 1 uint8_t 1 byte (0x01)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
checksum 1 uint8_t checksum = Σ(Byte[0..4]) % 256

[!WARNING]

The command to reset loop is only effective when the servo is in the released state. To ensure proper execution, it is recommended to first issue a stop instruction before performing the resetting loop.

command_0x01

0x12 0x4c 0x11 0x01 0x00 0x70

Example Explanation:

  • Assuming the current position is +489.9°,
  • Reset loop of the servo with ID 0, and re-record the current absolute position as the present position,
  • If we then send a read position command, the position read will be +489.9° – 360° = +129.9°.

15.3 Response (Optional)

16. Damping Control

16.1 Overview

  • Allow the servo to adjust to different positions under the action of external forces, and enable the setting of its execution power.
  • Command ID: 09 (0X09)

16.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Damping Control (0x09)
length 1 uint8_t 3 bytes (0x03)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
power 2 uint16_t execution power, unit: mW
If power = 0 or exceeds the power protection value, the execution will follow the power protection value
checksum 1 uint8_t checksum = Σ(Byte[0..6]) % 256

[!WARNING]

The damping control command is only effective when the servo is in the released state or damping state. To ensure proper execution, it is recommended to first issue a “Stop Instruction” before performing damping control operations. 

0x12 0x4c 0x09 0x03 0x00 0xf4 0x01 0x5f

Example Explanation:

  • Set the servo with ID 0 to damping control,
  • Set its execution power to 500 mW.(If power exceeds the power protection value, the execution will follow the power protection value)

16.3 Response (Optional)

17. Set Origin Point

17.1 Overview

  • Set the current position as the Origin Point of the servo via the command.
  • Command ID: 23 (0x17)

17.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Set Origin Point (0x17)
length 1 uint8_t 2 bytes (0x02)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
reset 1 uint8_t 0x00 (Default)
checksum 1 uint8_t checksum = Σ(Byte[0..5]) % 256

[!WARNING]

The set origin point command is only effective when the servo is in the released state. To ensure proper execution, it is recommended to first issue a “Stop Instruction” before performing setting origin point operations.

command_0x03

0x12 0x4c 0x17 0x02 0x00 0x00 0x77

Example Explanation:

  • Set the current position of the servo with ID 0 as its origin point.

17.3 Response (Optional)

18. Synchronous Instruction

18.1 Overview

  • The synchronous instruction is used to simultaneously send control information for multiple servos in a single command. Each servo matches and parses the corresponding parameters based on its unique ID, and only executes the content relevant to itself. After all servos have received the information, they start simultaneously, achieving coordinated and synchronized movement of multiple servos.
  • Command ID: 25 (0x19)

18.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Synchronous Instruction (0x19)
length 1 uint8_t (%d*%n+3) bytes
cmd_id 1 uint8_t Effective Synchronous Command id
length 1 uint8_t Effective Synchronous Command length : %d
count 1 uint8_t the count of servo : %n
content 1 uint8_t the content of effective command
checksum 1 uint8_t checksum = Σ(Byte[0..%d%n+6]) % 256

[!WARNING]

command_0x01

0x12 0x4c 0x19 0x11 0x08 0x07 0x02 0x01 0x2c 0x01 0xe8 0x03 0x00 0x00 0x02 0x58 0x02 0xd0 0x07 0x00 0x00 0xe5

Example Explanation:

  • Send synchronous instruction to the servos with ID 1 and ID 2,
  • Set the servo motor with ID 1 to move to the target position of +30° within 1000ms, configure the power protection value to the maximum execution power, operating at maximum power.
  • Set the servo motor with ID 2 to move to the target position of +60° within 2000ms, configure the power protection value to the maximum execution power, operating at maximum power.
  • Both servos will execute the commands simultaneously after receiving them.

18.3 Effective Synchronous Command

Command Name Command ID Length:%d
Single-Turn Position Control (Basic) 08 (0x08) 7 (0x07)
Single-Turn Position Control (Advanced – Time-based) 11 (0x0b) 11 (0x0b)
Single-Turn Position Control (Advanced – Speed-based) 12 (0x0c) 11 (0x0b)
Multi-Turn Position Control (Basic) 13 (0x0d) 11 (0x0b)
Multi-Turn Position Control (Advanced – Time-based) 14 (0x0e) 15 (0x0f)
Multi-Turn Position Control (Advanced – Speed-based) 15 (0x0f) 15 (0x0f)
Data Monitor 22 (0x16)

18.4 Response

  • The Synchronous Instruction does not have a response packet.
  • If the Effective Synchronous Command received by the servo with the corresponding ID has a response packet, then return the respective response data.

19. Asynchronous Write Instruction

19.1 Overview

  • Asynchronous writing is composed of a combination of an asynchronous write instruction and a effective synchronous command.
  • After the command is issued, the online servo will write the next Effective Asynchronous Command into its own buffer zone and execute it immediately upon receiving the Asynchronous Activate Instruction.
  • Command ID: 18 (0x12)

19.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Asynchronous Write Instruction (0x12)
length

[!IMPORTANT]

  • The instruction takes effect on all servos on the bus, and upon receipt, the buffer zone is activated.
  • The buffer zone is only permitted to store one Effective Asynchronous Command at a time.
  • If a servo with the same ID receives an instruction again, it will be executed as a regular instruction.

command_0x12

0x12 0x4c 0x12 0x00 0x70
0x12 0x4c 0x08 0x07 0x00 0x84 0x03 0xf4 0x01 0x00 0x00 0xe9

Example Explanation:

  • Step 1: Issue an asynchronous write instruction, and all online servos activate their buffer zones.
  • Issue a control instruction with ID 0, and write the content into the buffer zone.
    • Set the servo motor with ID 0 to move to the target position of +90° within 500ms；
    • configure the power protection value to the maximum execution power, operating at maximum power.

19.3 Effective Asynchronous Command

Command Name Command ID Length
Single-Turn Position Control (Basic) 08 (0x08) 7 (0x07)
Single-Turn Position Control (Advanced – Time-based) 11 (0x0b) 11 (0x0b)
Single-Turn Position Control (Advanced – Speed-based) 12 (0x0c) 13 (0x0d)
Multi-Turn Position Control (Basic) 13 (0x0d) 11 (0x0b)
Multi-Turn Position Control (Advanced – Time-based) 14 (0x0e) 15 (0x0f)
Multi-Turn Position Control (Advanced – Speed-based) 15 (0x0f) 15 (0x0f)

19.4 Response

  • There is no response packet for the asynchronous write instruction.
  • For the specific content of the response packet for a effective asynchronous command, please refer to 6.3. Response (Optional).

20. Asynchronous Activate Instruction

20.1 Overview

  • The asynchronous activate instruction is used to trigger the execution of commands stored in the buffer zone. Upon completion, the buffer zone is cleared and closed.
  • Command ID: 19 (0x13)

20.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Asynchronous Activate Instruction (0x13)
length 1 unit8_t 1 byte (0x01)
action 1 unit8_t 0x01: Cancel | 0x00: Execute
checksum 1 unit8_t checksum = Σ(Byte[0..4]) % 256

[!CAUTION]

  • Regardless of whether the instruction is executed or canceled, the servo buffer will be cleared and closed.

  • After power-off, the buffer content automatically becomes invalid.

command_0x01

0x12 0x4c 0x13 0x01 0x00 0x72

Example Explanation:

20.3 Response

  • There is no response packet for this instruction.

21. Read Data

21.1 Overview

  • By sending instructions, you can individually obtain the working status parameters (such as voltage, current, temperature, etc.) and configuration parameters of the servo; the relevant information is returned via response data packets.
  • Command ID: 03 (0x03)

21.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Read Data (0x03)
length 1 uint8_t 2 bytes (0x02)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
data_id 1 uint8_t Please refer to the working status parameters and servo configuration parameters.
checksum 1 uint8_t checksum = Σ(Byte[0..5]) % 256

command_0x03

0x12 0x4c 0x03 0x02 0x00 0x03 0x66

Example Explanation:

  • Read the current power of the servo with ID 0.

21.3 Response

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x05 0x1c)
cmd_id 1 uint8_t Read Data (0x03)
length 1 uint8_t 3 bytes (0x03)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
data_content 1/2 int8/16_t Based on the return values of the parameters read from the instructions, Please refer to the operating status parameters and servo configuration parameters.
checksum 1 uint8_t checksum = Σ(Byte[0..6]) % 256

response_0x03

0x05 0x1C 0x03 0x04 0x00 0x03 0x62 0x01 0x8e

Example Explanation:

  • The power value returned by the servo with ID 0 is 0x62 0x01. After unpacking, the obtained value is +354, indicating that the current servo power is 354mW.

22. Data Monitor

22.1 Overview

  • By sending instructions, the operating status parameters (such as angle, voltage, current, temperature, etc.) of servos can be obtained in batches; the relevant information is returned via response data packets.
  • Command ID: 22 (0x16)

22.2 Command

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Data Monitor (0x16)
length 1 uint8_t 1 byte (0x01)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
checksum 1 uint8_t checksum = Σ(Byte[0..4]) % 256

command_0x01

0x12 0x4c 0x16 0x01 0x00 0x75

Example Explanation:

  • Obtain the operating status data of the servo with ID 0.

22.3 Response

Byte Name Length Data Type Description
header 2 uint16_t Fixed identifier ( 0x05 0x1c )
cmd_id 1 uint8_t Data Monitor (0x16)
length 1 uint8_t 16 bytes (0x10)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
voltage 2 uint16_t Current operating voltage, unit: mV
current 2 uint16_t Current operating current, unit: mA
power 2 uint16_t Current operating power, unit: mW
temperature 2 uint16_t Current operating temperature, please refer to the ADC-temperature mapping table.
status 1 uint8_t Status indicator bit
position 4 uint32_t Current position, unit: 0.1°
turns 2 int16_t Current number of revolutions, unit:turn
checksum 1 uint8_t checksum = Σ(Byte[0..19]) % 256

[!TIP]

It is recommended to set a maximum waiting time, timeout. If no response is received within this time, it indicates that the servo is not online.

response_0x01

0x05 0x1c 0x16 0x10 0x00 0x83 0x1e 0x1e 0x00 0xea 0x00 0x2c 0x07 0x00 0xaf 0x0b 0x00 0x00 0x00 0x00 0xdd

Example Explanation:

  • By unpacking the response data of the servo with ID 0, the obtained operating status data is as follows:
    • ID: 0x00 = 0
    • Voltage: 0x1e 0x83 = 7811 mV
    • Current: 0x00 0x1e = 30 mA
    • Power:0x00 0xea = 234 mW
    • Temperature:0x07 0x2C = 1836 adc value
    • Status:0x00 = 0
    • Posotion：0x00 0x00 0x0b 0xaf = 2991 299.1degrees
    • Turn：0x00 0x00 = 0

23. Customize Configuration Parameters

23.1 Overview

  • Write the servo’s configuration parameters via commands.
  • Command ID: 04 (0x04)

23.2 Command

Command Length Data Type Description
header 2 uint16_t Fixed identifier (0x12 0x4c)
cmd_id 1 uint8_t Customize Configuration Parameters (0x04)
length 1 uint8_t 2 bytes (0x02)
servo_id 1 uint8_t servo ID, range 0 ~ 254 (0x00 ~ 0xfc )
data_id 1 uint8_t Please refer to the servo configuration parameters.
data_content n int8/16_t Please refer to the servo configuration parameters.
checksum 1 uint8_t checksum = Σ(Byte[0..n+6]) % 256

23.3 Response (Optional)

Appendix

A. operating status parameters

data_id Parameter Name Data Type Unit Notes
1 Voltage uint16_t mV
2 Current uint16_t mA
3 Power uint16_t mW
4 Temperature uint16_t ADC Please refer to the ADC-temperature mapping table
5 Status indicator bits uint8_t BIT[0] – Set to 1 when instruction is being executed, clear to 0 after execution is complete
BIT[1] – Set to 1 for instruction execution error, clear to 0 after next correct execution
BIT[2] – Set to 1 for stall protection, clear to 0 after stall is resolved
BIT[3] – Set to 1 for overvoltage protection, clear to 0 after voltage returns to normal
BIT[4] – Set to 1 for undervoltage protection, clear to 0 after voltage returns to normal
BIT[5] – Set to 1 for overcurrent protection, clear to 0 after current returns to normal
BIT[6] – Set to 1 for overpower protection, clear to 0 after power returns to normal
BIT[7] – Set to 1 for overtemperature protection, clear to 0 after temperature returns to normal

ADC-temperature mapping table

Temperature(℃) ADC Temperature(℃) ADC Temperature(℃) ADC
50 1191 60 941 70 741
51 1164 61 918 71 723
52 1137 62 897 72 706
53 1110 63 876 73 689
54 1085 64 855 74 673
55 1059 65 835 75 657
56 1034 66 815 76 642
57 1010 67 796 77 627
58 986 68 777 78 612
59 963 69 759 79 598

B. servo configuration parameters

data_id Parameter Name Data Type Unit Notes
33 Command Response Switch uint8_t 0x00: Do not send response packet (default)
0x01: Send response packet
34 Servo ID uint8_t Range 0 ~ 254
36 Baud Rate Configuration uint8_t 0x01 – 9,600
0x02 – 19,200
0x03 – 38,400
0x04 – 57,600
0x05 – 115,200 (default)
0x06 – 250,000
0x07 – 500,000
0x08 – 1,000,000
37 Stall Protection Switch uint8_t When the servo operates beyond the Power Protection Value
0x00: (Stall protection OFF) Reduce output to the power protection value (default)
0x01: (Stall protection ON) Release holding torque
38 Stall Power Upper Limit uint16_t mW
39 Voltage Protection Lower Limit uint16_t mV
40 Voltage Protection Upper Limit uint16_t mV
41 Temperature Protection Threshold uint16_t ADC
42 Power Protection Value uint16_t mW
43 Current Protection Value uint16_t mA
46 Power‑On Holding Torque Switch uint8_t 0x00: Release torque (default)
0x01: Maintain torque
48 Angle Limit Switch uint8_t 0x00: Off (default)
0x01: On
49 Power‑On Soft‑Start Switch uint8_t 0x00: Off (default)
0x01: On
50 Power‑On Soft‑Start Time uint16_t ms
51 Servo Angle Upper Limit int16_t 0.1°
52 Servo Angle Lower Limit int16_t 0.1°

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